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Hot or Cold tap water for boiling Pasta??

Is it an Old Wives Tale that you should boil cold water for making pasta??? I always heard that using hot water from the tap may contain chemicals/minerals that can contaminate the food...but obviously, cold water takes longer to boil.....

Silly question... but....

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  1. The reason why it is suggested you always start with cold water is simply....warm or hot water has been sitting in the pipes longer and may or may not have picked up something coming from the hot water tank heater. This may not be as much of a problem if your home is fitted with the newer super heaters and not the old water tank heater more common in older homes.

    1. the only difference is that hot water boils faster.
      if you use your hot water like a normal person there is no difference.

      1. Somewhere along the way, I was given to understand that unlike cold, hot tap water can contain lead leached from soldered pipes so should never be used for food or drink. Either in Cooks Illustrated or on America's Test Kitchen, there was a subsequent correction to their advice to start with hot tap water, citing this danger.

        4 Replies
        1. re: greygarious

          that's ancient times. lead solder went the way of the Dino many, many years ago....

          1. re: greygarious

            I can't speak for the US but in Canada they've prohibited the use of lead soldering materials since 1990. Lead still might leach into the water system from old lead mains, service lines etc but that would happen whether the water was hot or cold.

            http://www.hc-sc.gc.ca/ewh-semt/pubs/... (4.2.1)

            1. re: greygarious

              If you are worried in general, I'd get my pipes tested.

              The difference between tap water and hot water seems like a lot to us but considering absolute zero is like -460 deg f and lead's melting point is 621 degrees, the difference between hot and cold seems like it would be trivial to the lead. Running your water before using to "flush" seems like the bigger issue. (And nobody talks about all the carcinogens released by our gas stoves over the extra time to heat that water...)

              1. re: greygarious

                CPSC publication on the subject


                IF you suspect lead contamination:
                - let cold water run before using if the tap hasn't been used for 6hrs
                - don't use hot for consumption

                There have been limits on the lead content in solder since 1988.

                However I'd still like to see some quantitative study of the relative lead content from hot and cold taps. In a newer house with low lead solder there shouldn't be much of difference. Even in an old one, most of the lead may have already leached out of the solder in immediate contact with the water. Keep in mind that it is only that length of pipe from the hot water heater to the kitchen faucet that could make a difference. Hot water from the tank is only in contact with that pipe for a few seconds. The first draw will have been in contact with the pipe and its joints longer, but for most of the time it has been cool (you do let the water run a while till it gets hot, right?).

                Lead, if an issue, is more likely to be one for your morning coffee, when water has been sitting in the pipes overnight. By the time you make pasta, you have been using both hot and cold during meal prep.

              2. I had read somewhere that you should use cold water to start with for pasta, something about sediment etc.

                I dont use either nowdays. I use bottled water which is typically near room temperature.

                21 Replies
                1. re: swsidejim

                  Hot water leaches minerals that have accumulated on the walls of the pipes, so I always use cold water. I have a Brita pitcher, but I seldom use filtered water for cooking, except for making coffee/tea, or when baking.

                  1. re: Kelli2006

                    uhmmmm, where do you think those minerals come from? they come from the water, so if you use cold water they are in there too.

                    the only problem that may arise if your hot water system sits still for a looooong period of time., which i doubt would ever happen in a normal kitchen.

                    1. re: ScubaSteve

                      Yes, water has minerals in it, no matter the temperature. Many of these minerals are water soluble and and dissolve at high temperature. When you turn on the hot water, the pipe is most likely cold. As the water travels from the heater through the pipes, the minerals will harden on the suface of the pipe and form layers of minerals on the pipe. These minerals will dissolve back into the water when it runs hot through the pipe again, resulting in a higher concentration of minerals in the hot water that comes out of your tap than in the cold water.
                      Some of these minerals may be harmful to your health, i don't know. What i do know is they can make your food taste kind of "tinny".
                      (also if you do sugar work, this can really mess with the crystalisation of the sugar, always use cold water for sugar!)

                      Most of the chemicals that go into pipes are soluble in cold water too, so I don't think it makes a difference for the chemicals...

                      I've also heard something about cold water coming to a boil faster than hot water will. I have no idea how to explain that one, or if it's true...anybody?

                      1. re: hungryungry

                        No, it is not true. Hot water boils faster than cold water. End of story.

                        1. re: hungryungry

                          It's not only not true, it's nonsensical. When you heat cold water, it becomes hotter, and at some point it's the same temperature as the hot water from the tap, so they're both "hot water"! I think this bizarre but common misconception is based on the fact that the closer water gets to boiling, the more energy (and thus time, if you're heat source is producing heat at a constant rate) it takes to increase the temperature. Thus, it takes slightly longer to heat 210 degree water to 212 degrees than it does to heat 80 degree water to 82 degrees. But it makes no difference if your 140 degree water was heated in a water heater and or on the stove, except for the small difference caused by putting the hot water from the tap into a cold pot.

                          If you're worried about hot water leaching minerals from the pipes, then let it run for a few seconds until the water that's been sitting in the pipes is flushed out. Water that's moving through the pipes is not going to leach minerals in the few seconds it passes through the pipes. Furthermore, any water that's hot hasn't been sitting in the pipes long, since it starts to cool as soon as it leaves the water heater.

                          1. re: Ruth Lafler

                            haha! thanks, for the explanation, I really didn't think that one made much sense...

                            1. re: Ruth Lafler

                              It's not only not true, it's nonsensical. When you heat cold water, it becomes hotter, and at some point it's the same temperature as the hot water from the tap, so they're both "hot water"!

                              While this is true....the difference is hot water from tap is water heated...but never boiled and from a water heater that has mineral build up and whatever else inside it floating for years. I can recall my own home water heating lasting over ten years...yes I emptied the bottom on a regular basis, but still I do not know what remained inside.

                              When you start with cold tap water and boil on a stove(or other heat source) it becomes hotter than simply "hot water"......and from what I have read, the water is changed due to evaporation and loss of an amount of oxygen during the boiling process....

                              Whatever this does to the water....I will leave to a scientist to chime in.

                              1. re: fourunder

                                Water is water. The laws of physics are the laws of physics. The slight variations in mineral content from various sources aren't enough to make a difference in how fast water boils.

                                1. re: Ruth Lafler


                                  My comments had to do with whether the water started from the hot water heater or not.....not just minerals....but other impurities as well.

                                  1. re: fourunder

                                    You're starting from the unproven assumption that (1) there are significant amounts of impurities in tap water, and (2) there are significantly more/different impurities in tap water that's been heated in the water heater than there are in water from the cold water tap, and (3) these impurities somehow change the rate at which water changes temperature. But as I said, why don't you just try it for yourself.

                                    1. re: Ruth Lafler

                                      1 and 2 .....I'll bet you on any day

                                      3.....I mad no such claim and or assumptions

                                      But as I said, why don't you just try it for yourself.

                                      I never said I cared about how long it takes to boil water...but I do know it takes longer for cold to boil....anything else?

                                  2. re: Ruth Lafler

                                    are you quite sure about that? (I'm not trying to be confrontational, just curious, really) Because doesn't adding salt to water change it's boiling point? So couldn't other minerals also alter the properties of the water?

                                    1. re: hungryungry

                                      See above re: unproven assumptions about the difference in "impurities" between water from the water heater and water from the cold tap.

                                      Adding salt to water changes the boiling temperature slightly. And when you add salt there's a much larger concentration than these hypothetical other minerals -- you can, after all, taste the salt. And finally, this discussion isn't about the boiling point of water, it's whether cold water comes to a boil more quickly than hot water. Even if the boiling point of the water from the water heater is slightly different -- and thus the hot water has to reach a higher temperature -- it's not going to be enough difference to make up the 60-80 degree "head start" that water from the water heater has over water from the cold tap.

                                      Here's one guy who tried it: http://itotd.com/articles/521/water-f...

                                  3. re: fourunder

                                    "When you start with cold tap water and boil on a stove(or other heat source) it becomes hotter than simply "hot water" "


                                    Is anyone really making spaghetti in just the "hot water" that comes out of the tap? I, for one, am boiling the water regardless of whether I start with hot water or cold water. So when the water comes to a boil, it's all the same temperature no matter where it started out.

                                    Sort of like which weighs more: a pound of bricks or a pound of feathers?

                                    1. re: valerie

                                      The issue was the surprisingly common notion that cold water comes to a boil faster than hot water.

                                      If anyone actually has any doubts, it's easy enough to tell for yourself: measure the same amount of hot tap water and cold tap water into two pots, put them on the stove and see which one boils first.

                                      Go ahead, try it and report back.

                                      1. re: Ruth Lafler

                                        Not sure if you are responding to my post above, Ruth. Because if you see my post from earlier today, you will see that I get it.

                                        1. re: Ruth Lafler

                                          ahh, But i dont have two identical pots....
                                          And anyways it wouldn't be nearly as fun as this...

                                          1. re: Ruth Lafler

                                            This has been being debunked for decades - the explanation (the debunking explanation) I was given when I was a little kid is that cold water holds more gas(s) than hot, especially when hot means hot water sitting around in a tank-style water heater. Apparently a lot of people are prone to thinking water is simmering/boiling when they see bubbles rising to the surface, being ignorant of the difference between dissolved gases being released and the non-bubble-ous agitation you get when liquids do actually boil. So on the one hand, cold water does "something" faster than hot when you heat them, but that something isn't "boiling," it's de-gassing, for lack of a better word...

                                2. re: swsidejim

                                  You use bottled water to cook pasta? Wow. That's a lot of water.

                                  1. re: lawgirl3278

                                    yes, gallon jugs of bottled water for all cooking(pasta, stock, rice, etc.). Unitl the new water facility under construction is finished where I live I wont use the tap water for cooking, or drinking(it tests high for radium occasionally)

                                3. jfood uses hot water for pasta as it takes less time to boil. He has a well and the water is tested annually. Eben when he lived with city water he used hot water.

                                  If anyone tells you the "chemicals" from leaching is a reason to start with cold, then remind them they take hot showers with the same water and their pores allow anything they are fearful of into their system.

                                  Not a silly question at all, but there are waaaaay more things jfood worries about in the food chain.

                                  1. Michael Chiarello says "Always start with cold tap water. Hot water has been sitting in the water heater, where it has gotten stale, flat, and tired. Remember, water is an ingredient, so how it tastes makes a difference. "

                                    I always try to do what Michael Chiarello (swoon swoon) says.

                                    3 Replies
                                    1. re: laliz

                                      and before your cold water comes to a boil it will also be stale, flat and tired (whatever that means).

                                      1. re: ScubaSteve


                                        I am in the Coffee Service business....where we supply coffee makers to businesses who purchase our products. Anyway, the coffee makers whether pour over or automatic models, heat the water and the water while it is held in a reservoir tank. Now in my company, we clean these tanks on a regular schedule of every six months. If you saw the build up of minerals and etc....of what is inside these tanks.....you would not address this issue so nonchalantly.

                                        1. re: fourunder

                                          i have seen what U are talking about, my GF works for *$'s.

                                          all i'm saying is that if you have a normal kitchen your hot water runs often enough so that any deposit or mineral or whatever that makes it into your hot water tap and then gets absorbed into your pasta is so small that it may as well be considered zero.

                                          and i don't think i'm being non-chalant, just practical.

                                    2. I thought it was just simple economics. It is cheaper to boil a pot of cold water on a stove top than to heat it in a hot water heater and keep it hot.

                                      3 Replies
                                      1. re: Passadumkeg

                                        Feel the outside of your hot water heater; do the same on the pasta pot. Which is loosing more heat to its surroundings?

                                        Do you salt your pasta water? Think of all the minerals in that water.

                                        1. re: paulj

                                          Yup. Your water heater is already keeping 40 gallons (or more) of water hot. Drawing off a gallon to boil your pasta isn't going to make an appreciable difference.

                                          1. re: paulj

                                            Thanks, Ruth. Paul, no I don't usually salt the water, but I had a physical on Mon. and for an old fart, I'm in amazingly good health. And as far as minerals go, I've been exposed to agent orange, wounded 2 1/2 times, worked underground in a uranium mine for 3 years (I don't need a night light), am in the sun all the time as a registered Maine guide, and I'm gonna worry about a little salt? Last night I salted the water, for the first time in years (w/ Baltic sea salt, of course) for a big pot of spaghetti carbonara!
                                            ps worked 4 hours yesterday w/ a chain saw in 15 degree weather and then split the wood and stacked almost a cord of wood to heat my house. My back is a bit sore, however.
                                            Oh, yes Happy New Year!

                                        2. How about introducing another 'impurity' to the discussion? Chlorine used to purify (as in kill bacteria) the water. Is there a higher or lower concentration of it in freshly drawn cold water, or hot water that has been in the tank some time? Does it affect food taste or cooking qualities?

                                          If you don't notice a difference when brewing your tea or coffee, then you shouldn't notice one when boiling pasta, or cooking rice.

                                          I suspect that if there are significant differences in the mineral content of your hot and cold water, that you should have the water pipes and heater checked. How old is that heater? Most don't last more than 10 yrs. How old are the water pipes? Possibly as old as the house.

                                          2 Replies
                                          1. re: paulj

                                            Chlorine dissipates as water sits -- that's why you let the water sit overnight before putting it in a fish tank. Thus, if there is a difference, the water from the water heater should have less chlorine than water fresh from of the water supply.

                                            1. re: Ruth Lafler

                                              paulj did you take high school chemistry?

                                          2. The easiest and most practical way to make a decision is to run your hot water until it's hot. Fill a glass and set aside. Run the tap until the cold water is cold. Fill a glass and set aside. When they are both "room temperature," taste them. If there is no taste difference, doesn't matter. If one tastes better than the other, use it.

                                            1. A hot water heater holds 30 or 40 gallons of water. When you use a quart or two to cook, fresh water comes in and mingles with the 39 an a half gallons that are already in there. This happens every time you use hot water. A little bit out, a little fresh with the bulk. It is possible that some of the water in the tank has been there since the tank was installed. And water does go bad. A plumber once told me "Never use water from a hotwater heater for anything but washing."

                                              11 Replies
                                              1. re: ChrisOC

                                                Hot water comes out the top of the tank; cold enters near the bottom. Since water rises as it gets warmer (assuming temperatures above 4C), I'd say that the hot water you draw for pasta is no 'older' than the last long shower.

                                                1. re: paulj

                                                  Yup. Cold water in the bottom, hot water out the top -- that's how you can have running hot water, instead of a few seconds of hot water and then cold water. And another thing: water doesn't "go bad." Really, it doesn't. If you keep it in a sealed container for a long time it goes flat (the dissolved oxygen comes out), and the reason they want you to exchange out your "emergency" bottled water is that after a long period of time it could be developing some bacterial growth (unlikely, but those safety experts are pretty fanatical). But in a situation where it's constantly being mixed with fresh water, even that doesn't happen.

                                                  Plumbers are just as susceptible to myths and old wives tales as other people. In fact, some of the most ridiculous things I've ever heard have come from plumbers, carpenters, electricians, etc. who should have known better.

                                                2. re: ChrisOC

                                                  I want to thank you all for your profound responses to what I just thought was a silly little question....Reading all your posts hasn't provided me with a definitive answer to this issue, but I chose this morning to ponder why the "Tournament of Roses Parade" is on 3 TV networks..is that how I want to start the New Year...NOT
                                                  So I chose to conduct a Physics Experiment:

                                                  I put 3 cups of cold tap water and 3 cups of hot tap water in a Wolfgang Puck 2 QT stainless steel saucepan on a gas stove, and turned the burners on full tilt

                                                  The cold water boiled in 7 minutes 31 seconds, the hot in 6 minutes 44 seconds

                                                  Hypothesis: Hot water boils faster!!!!!!!! However, mitigating factors could be the location of the pot upon the burner, or variances in the flow of the flame from the burner proper due to drafts in the air......

                                                  I will accept the prevailing wisdom in your posts and the sage advice of Mr. Chiarello and always use COLD WATER to boil

                                                  HAPPY NEW YEAR EVERYBODY!!!!!!!!

                                                    1. re: Passadumkeg

                                                      This is almost as much fun as the old "hot water freezes faster that cold water"

                                                      1. re: ChrisOC

                                                        Either. Used both, no difference.

                                                        1. re: ChrisOC

                                                          The freezing issue is called the Mpemba effect. See the link below, it's very facinating.


                                                        1. re: paulispumonti

                                                          Technically cold water does boil faster then hot in a way. It depends how you look at it. The cold water probably about 50 degrees or so went from that 50 all the way to the 212 mark. Thats 162 degree increase. The hot went from about 140 degrees to 212. Only 72 degrees.And as you stated there was only 47 seconds difference!

                                                          Obviously if you put almost boiling water in one pot and cold water in another pot the hot will reach boiling first but the rate of temperature change in the cold will be much faster. Thats what brought this whole myth to life.

                                                          And think about this... when somebody says hot water... how hot? 90 degress or 200 degrees? How cold?

                                                          Excellent thread though Paul. People loved it. I had a blast reading all the responses : )

                                                          1. re: Mojin6

                                                            Harold McGee is trying to make the case for cooking pasta in a much smaller amount of water, and even starting with the pasta in cold water!

                                                            1. re: paulj

                                                              Well, I never use as much water as they say --- I figure as long as there's room for the water to circulate and the pasta to move freely and expand without sticking there's enough water.

                                                      2. I start with cold water to boil pasta. Depending on the age of your hot water heater and pipes, you may experience a difference in taste between hot and cold taps. The hot water heater will accumulate deposits over time that change the taste of the water and anything you cook in it. It may take a few minutes longer to reach a boil with cold water, but I prefer the taste. I add a pinch or so of salt to increase the boiling point of the water, not to salt the pasta. I prefer the taste of Chateau d'Sink over the filtered stuff from the front of the fridge, and some bottled water brands over others.

                                                        People who say they aren't bothered by the build up of sediments have never had an opportunity to drain and replace a hot water heater, or like me, they may prefer one tap over another.

                                                        2 Replies
                                                        1. re: geppetto

                                                          I start with cold tap water and alot of salt to flavor the pasta.
                                                          I recently got a Noritz installed and got rid of the hot water heater for good. I love having the endless hot water and never have to worry about replacing yet another water heater that's rusted out & leaking

                                                        2. I've used water from the hot tap to make tea. It tastes different, and there is sediment in it. Of course, this may be something to do with the age of the building (I think Georgian), but we don't have an old-style boiler.

                                                          But I heard that some building killed a load of people off when their water-tower contained legionaires disease. One sec:

                                                          1. Sorry, double post. Here:

                                                            And this explains it a bit better:

                                                            It says about sediment providing nutrition for the bacteria and
                                                            "Legionella is most likely to proliferate in water systems that have a temperature between 20C and 50C. Human blood temperature of approximately 37C is the most ideal temperature for proliferation. Stagnant water within the above temperature range appears to provide the ideal conditions for proliferation of Legionella."

                                                            But it dies at 60C apparantly. Better be safe than sorry.

                                                            Come to think of it, I did have a bout of flu shortly after drinking that tea.

                                                            1 Reply
                                                            1. re: Soop

                                                              You make tea with water straight out of the tap? 'Cause most people boil water to make tea, which kills everything. Most water heaters keep the warmer than 50 degrees Celsius (122 degrees F.).

                                                              The water systems that produce Legionella aren't drinking water systems, but heating/cooling systems, since Legionnaires' disease isn't caused by drinking water, but by inhaling bacteria-laden water particles suspended in air.

                                                            2. Having just read through this thread, I can't help but post the following logical question. Several posters claim, and cite various industry "expert" types (such as plumbers, coffee machine techs, etc.) as saying, that hot tap water has more minerals than cold tap water because the hot water heater is full of mineral deposits that get into the water when it heats it and those minerals come out your tap. These extra minerals are variously "bad" for you, make hot water boil slowly, destroy pasta, whatever.

                                                              Now, here's my question, which I don't think anyone brought up before. Since the water in your house all comes from the same input pipe (source), it all starts with the same minerals. If the hot water heater is taking out some of these and depositing them in itself, then isn't the hot tap water LOWER in minerals than the cold tap water?? Answer: yes it is.

                                                              Which once again makes one wonder about some of the things that get stated as facts.

                                                              15 Replies
                                                              1. re: johnb

                                                                Now, here's my question, which I don't think anyone brought up before. Since the water in your house all comes from the same input pipe (source), it all starts with the same minerals. If the hot water heater is taking out some of these and depositing them in itself, then isn't the hot tap water LOWER in minerals than the cold tap water?? Answer: yes it is.
                                                                Sorry, but I would argue the answer is no...The input water source comes from a much larger pool, so parts per whatever, whether mineral, sediment or other impurity, is much less concentrated than from a 55 gallon or less home water heater. Also, as it has been suggested from another poster in this discussion who argues the same view as yours, the deposits at the bottom of the water heater is "sludge". her description, not mine.

                                                                Some questions for you...have you ever purchased bottled water for you home to consume for a non-emergency? Have you ever offered a guest in your home bottled water to drink? Have you ever cleaned out a coffee maker with vinegar or other substance??? If so, I can only surmise it has to do with either a maintenance issue or taste. When you make a soup, stew or braising liquid, do you use hot water from the tap as well?

                                                                For anyone who uses hot water to start a boil...that's fine with me.....I just prefer to use cold.


                                                                1. re: fourunder

                                                                  The fact that the "sludge" is in the water heater means that it's *not* in the water coming out of the water heater. It can't be in both places! The fact that there is sludge in the water heater means that less went out than went in.

                                                                  If you switched the tank around so you were drawing water off the bottom (which you don't), or if you stirred the sediment back into the water every week (which you don't), then the water from the hot water tank would have more sediment (at least in the short term), but if it were picking up sediment from the tank on a regular basis, then there wouldn't be any sediment in the tank! The sediment is coming out of the water, not going into it! The longer the water sits, the less sediment it has: moving water carries more sediment than still water.

                                                                  1. re: Ruth Lafler


                                                                    and then when you figure that only a small amount of water is actually being absorbed into the pasta the amounts of impurities you may be ingesting drops even further.

                                                                    1. re: ScubaSteve

                                                                      I know this is a bit late in the day, but I just want to say that you are dishing out some very bad disinformation. For instance, the notion that lead solder, etc. is no longer used in the U.S. may be technically correct, but there are many older homes that still contain it. Many heavy metals, PCBs, and other organic contaminants adhere to the inside of pipes and water heaters in a kind of calcareous accretion which typically renders them inert, UNTIL hot water dissolves them and sends them out your tap. The amounts may be small, but this is very important -- there is NO safe level for lead. None! The EPA can say what it likes, but they've been wrong before. No lead is safe, no matter how small the PPB. This is especially true for developing fetuses and small children. What's more, even healthy adults can develop hypertension or even psychiatric issues from years of ingesting small amounts of lead. Lead builds up in bone and other tissues. The same is true for mercury and other heavy metals. You can make your coffee with hot tap water if you like, and perhaps you will live to a ripe, healthy, old age, but then again, if you develop some strange neurological disorder or raging high blood pressure, don't say you weren't warned.

                                                                  2. re: fourunder

                                                                    I think you're confusing a hot water heater with a distillation apparatus. If you distill, you boil off water which leaves impurities behind in greater concentration. But a hot water heater doesn't do that. It is a closed system that merely heats the water. Nothing is lost in the process---go down and look at your water heater---you will notice there is no steam rising off it---in fact, it should be heating the water to only 120-130 F---any hotter is dangerous, and that's a long way from boiling in any case. So whatever impurities come into the tank leave unless they are deposited within, and if that happens less go out.

                                                                    It is possible for a poorly designed or built WH to rust a little, and in that case one might get some ferrous oxide in his hot water. However, if this is happening, you will likely soon be getting a new water heater, so it shouldn't be a long term issue. And you won't need as much Geritol. It is also possible that the anode, which is sacrificing itself to prevent your tank rusting, may put out a bit of something--I doubt it would affect your pasta, but somebody more knowledgeable than I will have to comment on that.

                                                                    As to my personal water habits, I have a 1200 ft. deep well that produces very clean nice water, so there is no issue. I constantly castigate my wife for buying Aquafina, which given our excellent tap water I consider to be a total waste of money in addition to the environmental downside. I don't use hot water for cooking, mainly because it is a long run from my HWH and thus wastes a lot of gas reheating all that extra water. Also, I have an instant HWH, tho I'm not sure whether that's relevant to any of the matters under discussion here.

                                                                    The answer to many of the questions posed in this thread depends a lot on one's own water source. If you have a good source, you should act differently from those with a lesser source. For example, I'm always amused at people in NYC who buy bottled water. NYC has about the best water there is (and it's generally unmetered to boot)!! Most of it is pure rainwater and is so clean and soft (free of minerals) there is no need to treat it. Now if you live in, say, Memphis and get your water out of the Mississippi (do they?), well given what is in there by the time it gets to Memphis perhaps second thoughts would be appropriate.

                                                                  3. re: johnb

                                                                    John, it's good to have a curious mind, and it's good not to accept everything at face value. Here's an acid test for you to figure out what works best in your present situation. Draw a flask full of cold water from your cold water tap. Turn on the hot water, let it run long enough that you're sure the cold water in the pipes has been displaced by water from your hot water tank. You can even let it run long enough to get hot if you wish. Draw a flask of that water. Send them both off to a lab for analysis and make your decision based on the results. And one more test too.... Let both the hot water and cold water from the tap gain room temperature, then taste them and see which tastes best.

                                                                    The simplistic side of your "well, if all the chemicals from the hot water are in the bottom of the tank" argument is specious. There are all sorts of possibilities based on the age of the tank, the age of the house, plastic pipes, copper pipes, concrete pipes. People have already mentioned leached lead content from copper plumbing. If the sediment in the bottom of the water tank is agitated by new water rushing in to replace the water being drawn and the chemical sludge gets mixed into the water, you WILL get it in your pasta pot when you draw hot water to cook with.

                                                                    Basically, there are nearly uncountable variables. The only circumstance I know of when there is no possible dire consequence to using hot tap water to cook with is if you have a whole house water filter and an "on demand' hot water heater. No problems there. It's just basic common sense. Think it through!

                                                                    1. re: Caroline1

                                                                      If the "sediment in the bottom of the water tank is agitated by new water rushing in to replace the water being drawn" were happening on a regular basis, the sediment wouldn't be accumulating in the first place. Where do you think the sediment comes from? It comes from the cold water entering the tank -- the same cold water you're suggesting is a better! Furthermore, the water "rushes" in at the bottom of the tank, and the water is drawn off the top of the tank, the tank is several feet tall, and the sediment is heavier than water, which is why it's on the bottom in the first place. How, again, is the sediment at the bottom getting into your pasta water?

                                                                      I don't see how people are continuing to argue that somehow the fact that there's sediment in the water tank means there's more sediment in the water, when the whole reason it's in the tank is that IT'S SETTLED OUT OF THE WATER!!!!!!!

                                                                      Furthermore, lead cannot leach into your water in the few seconds the water is travelling from the water heater to the tap. If you're worried about that, flush the taps -- if the water has been sitting in the pipes long enough to leach lead (assuming your pipes even have lead), then the water isn't hot anymore any way. BTW, plastic pipes aren't used for supply lines, only for drain lines, which, obviously, has no effect on the water before you use it.

                                                                      1. re: Ruth Lafler


                                                                        You're pretty right, except that nowadays plastic is indeed used for supply lines. Unless there are code issues in a specific area, or an owner was willing to pay the difference, I doubt there many houses less than three years old anywhere that have anything other than plastic pipes, and that includes hot water lines (and it could go a lot further back than that).

                                                                        I base the three year thing on a discussion I had with my plumber, who told me he was the last one locally to make the switch, and my house is three years old (I don't know how far back he made the switch). I suspect the area I'm in (North Carolina mountains) would have been one of the last holdouts--it's one of those holdout type places.

                                                                        1. re: johnb

                                                                          I was curious, so I looked it up -- plastic (CPVC) water supply lines only became code in California in 2008.

                                                                          Ick. I'm glad I have copper with lead-free solder!

                                                                          1. re: Ruth Lafler

                                                                            California---always behind the rest of the country!!!! :)

                                                                            1. re: johnb

                                                                              More like in the forefront of being very rigorous before allowing "environmental exposure" to new chemicals (see, Proposition 65, the Safe Drinking Water and Toxic Enforcement Act of 1986). I'm certain before they could approve it they went through massive studies, public comment, etc.

                                                                        2. re: Ruth Lafler

                                                                          Oh dear. Well, in the first place, Ruth, the particulates of the sediment are not sieved and graded into uniforms size. Some parts are small, some are large. The water coming into the tank at the bottom hits the area where the sediment settles, thus maximizing the agitation. I did not say that ALL of the sediment will be drawn into the pipes, but if enough of the smaller particulates are agitated enough, they certainly will. It never occurred to me that I needed to get this basic.

                                                                          As for leaching lead, you do understand that the entire hot water system is a CLOSED system, don't you? And water IS fluid. There is no air in the system, so it is water water everywhere! There are soldered joints in older systems (and newer, I know people who insist on copper pipes today, regardless of cost) that are very near the water tank, not just way down the line. Close enough that induction currents inside the water heater may well pull the leaching lead contaminants into the tank, as well as pushing them down pipe from the tank. We're dealing with fluid here. Lead contact with water is not as much of a problem in older systems as it is in new systems as time will lead to a protective build up of calcification and sedimentation that "seals" the lead from maximum exposure. Well trained plumbers are also fairly successful at minimizing the amount of solder required to seal a joint. DIY solder projects can be questionable. Again, things so basic It never occurred to me it would not be understood.

                                                                          And as John has already explained to you, no, plastic pipes are not restricted to drain lines. I'm not certain, but in many areas you can access building codes on line, including city, state, and federal codes. Building codes cover plumbing and such issues in detail.

                                                                          1. re: Caroline1

                                                                            I don't know what you mean by the hot water system being a 'closed system'. Cold water comes in from the city supply, entering the tank near the bottom. As the water is heated it rises. Hot water is drawn out from the top and to your tap. In effect, water flows through the tank, with a certain residence time in the tank.

                                                                            The slow build up of sediment in the bottom of the tank is a clear indication that, on average, more enters the tank in the cold water, than leaves via the hot. Cold entering may stir up the sediment a bit, depending on where that orifice is relative to the sediment, and its orientation. But during the heating, and the rise to the hot water exit, most of that sediment will settle back down. First draw in the morning should have less; the cold water after a long shower will have more.

                                                                            But what is the relevance of this sediment? The pasta isn't going to absorb it.

                                                                            Lead from solder joints in the hot water feed line may increase the lead content of the hot water that passes through. I have doubts about that 'induction currents' business; can you give a reference on that? Low lead solder has been mandated for a number of years (since 1988?). I quoted a government source that say that IF you are worried about lead, use the cold water. That doesn't mean that most of us need to be worried about lead in our hot water.

                                                                            If there is a difference in taste between your hot water and cold, I suspect it has to do the presence, or absence, of dissolved gases, oxygen and chlorine, due to the fact that the water has sat, hot, in the tank for some time. If you suspect a difference in sediment, you can easily test that by drawing samples, and let any sediment settle.

                                                                            1. re: Caroline1

                                                                              (1) Lead is not a problem in new systems, because lead-free solder has been required for 20 years. But hey, as you've often told us, you're 75 -- maybe you need to update you opinions with the times.
                                                                              (2) Cold water has sediment, too. For the umpty-umpth time, where do you think the sediment in the hot water tank comes from? On average, the water coming out of the tank has less sediment than the water coming out of the cold water tap, as demonstrated by the buildup of sediment in the tank.

                                                                              1. re: Ruth Lafler

                                                                                talk to a plumber though, and I've heard that they sometimes use lead soder to fix pipes because It's easier and quicker even though they aren't supposed to.
                                                                                If they get caught though, they have to repipe the whole building!

                                                                      2. I always start with whatever temperature water comes out of the tap.


                                                                        I can draw off a gallon of whatever-temperature water in twenty seconds or so, but my hot water heater pipes take a long time to heat up and I'd have to run the water for a minute just to get it hot. Water is expensive and precious in the desert, and it's cheaper to run the burner on the stove for an extra minute than to let the water run.

                                                                        It's the same reason why I set my spicket to "burning hot" when doing dishes -- the first water in the sink is probably room-temperature at best, but by the time I fill the sink to the level I need for washing dishes, it has gotten much hotter than I want and it evens out without wasting any more water than is necessary.

                                                                        All the water is fully aerated by the time it boils, so I'm not worried about that either.

                                                                        12 Replies
                                                                        1. re: Das Ubergeek

                                                                          Good point! I don't live in the desert, but water's precious to me too, so I start with cold, and I do the same as you when i fill up the sink for dishes. Even if the minerals in the water thing is a myth (which I don't believe) at least your saving water!

                                                                          1. re: hungryungry

                                                                            in california, i've been warned against drinking from the tap, so i just use bottle water for everything!! is it harmful to use the tap for cooking?

                                                                            1. re: grabtrees

                                                                              Who is warning you about the tap water? Your local water district? the state? or a purveyor of bottled water?

                                                                              1. re: grabtrees

                                                                                Not at all. Sometimes they get a little chlorine-happy, which isn't dangerous, just badtasting -- buy a filter.

                                                                                1. re: grabtrees

                                                                                  In California unless you're on a private well I wouldn't worry about the tap water being safe (see comments about Proposition 65, above). The water is not "harmful" although depending on where you live, the water may or may not taste good. I lived in the Santa Barbara area for several years, and the tap water tasted hideous and left nasty mineral deposits, but it wasn't harmful -- I used it for cooking, although not for drinking or washing my hair (sticky!), but that was an aesthetic choice.

                                                                                  Lots of people assume that if their water tastes bad, that it's unhealthy, but that's simply not the case: the minerals that make the water taste bad are harmless (except in certain specific medical conditions), and if there were harmful chemical contaminents they wouldn't necessarily have any detectible taste. Did you know that in some places there are epidemics of tooth decay among children caused in part by the fact that they're only drinking bottled water and not getting the benefits of fluoride in tap water?

                                                                                  Drink tap water! It's better for the environment and your pocket book!

                                                                                  1. re: Ruth Lafler

                                                                                    well moments ago on the Food Networks "Food Detectives" with Ted Allen, it was determined that a) hot water boils faster b) always use cold tap water for cooking as hot water contains impurities including lead.....

                                                                                    and more importantly NEVER DOUBLE-DIP!!!!!!!!

                                                                                    1. re: paulispumonti

                                                                                      Did they give any quantities regarding lead in the hot water, or was it just a generic warning?

                                                                                      1. re: paulj

                                                                                        Very generic..the segment was about 2 minutes....the chowhounders are much more in depth.... I am sincerely humbled that my original simple question has provoked all these responses relative to physics, science, and the safety of our water supply!!! ...and this is all about what we do with our water at home.....

                                                                                        What do you think happens in most restaurants????...I've worked in them for years....most everything comes out of a tap, and very few restaurants can afford filtration systems!!!!! YIKES!!!!!!

                                                                                        1. re: paulispumonti

                                                                                          Why should we be concerned that restaurants use tap water?

                                                                                          Anyhow, on a lighter note, if they did use bottled water to cook pasta, for example, they'd probably try to charge us $20 extra for the bottled water! :-) (Of course I wouldn't be surprised if this has already happened.)

                                                                                  2. re: grabtrees

                                                                                    Apparantly a quarter of a bottle of water (I don't know if they mean price or volume) is the amount of petrol it costs to transport it. And also, it's imported from places like Hawaii, who are then left to drink unclean water. Bottled water = insanely bad for the world.

                                                                                    1. re: Soop

                                                                                      If you have access to good tap water, then extensive use of bottled water wastes resources. But as a means of distributing water to places and people who don't have such access it isn't bad. The PETE plastic is one of the most recyclable plastics. Bottles can even reused in water purification processes. Laying a clear bottle out in the sun for half a day kills most of the pathogens with UV rays ( the process is called solar water disinfection http://www.sodis.ch/ )

                                                                                      1. re: Soop

                                                                                        Hawaii has perfectly safe tap water just about everywhere as far as I know. But your essential point is correct--bottled water is very questionable from an environmental standpoint.

                                                                                2. Good question, I always heard my mother say to use cold water because it's better than hot and tastes better when it comes to a boil, same for the kettle so I don't know what's behind this.

                                                                                  2 Replies
                                                                                  1. re: BamiaWruz

                                                                                    In Yiddish we call that a "bubbeh meisseh" (rhymes with "rub a nice-a") -- a "grandmother story" that is usually ungrounded in fact.

                                                                                    1. re: Das Ubergeek

                                                                                      Another bubbeh meisseh. Cut off the ends of a roast when putting it into the pan for baking! My Grandmother always did this.

                                                                                      She, of course, didn't realize that it was because the roast was too long for the pan to begin with.

                                                                                      So who are you going to believe, old tales or scientific fact. Basic thermodynamics, like we all learned in high school (at least if you were lucky enough to go to Brooklyn Tech)...it takes less energy to excite the molecules of water to raise already hot water to 100 degrees centigrade (212 degrees to normal people...ie, boiling) than the sluggishly moving molecules of cold water.

                                                                                      Basic sech'l (and not a bubbeh meiser!)

                                                                                      How else would you boil the luxshin in koogl?

                                                                                  2. Have you ever returned a plate of spaghetti in a restaurant to the kitchen complaining they used the wrong flavor of water?

                                                                                    Gad...it's all in the mind, you know.

                                                                                    1. Always use hot water, because the water heater heats the water more efficiently than the stove, so you save energy, money and time. Other than that there's no difference. If you're making drinks it's a different story, because of the dissolved oxygen (more in cold water) which affects the taste; but for pasta it doesn't make a bit of difference, because the water should be boiling before you add the pasta anyway.

                                                                                      Also, my pet peeve on this thread: it's a water heater, not a 'hot water heater.' Water comes in cold, and goes out hot. Hot water doesn't need to be heated. Sorry for the pedantry....

                                                                                      1 Reply
                                                                                      1. re: Bat Guano

                                                                                        More efficient to pour cold water into the kettle and then pot this into the pan.

                                                                                        It may well be that you have a specific water heater, rather than a combi-gas boiler though.

                                                                                      2. I use a filter at the tap that is not supposed to have hot water run through it, so my choice has been made for me.

                                                                                        1. Copper pipes don't accumulate sediment to any noticeable degree and if you run into lead, it's probably a very old sewer line- the joints used to be stuffed with oakum and lead poured over it. Water heater tanks, however, often have serious sediment buildup, to the point where the capacity drops noticeably, and operate at temperatures that many bacteria can survive, even thrive in; hot tap water is not something you want in your food.

                                                                                          1. Only my cold water is filtered at the tap, so that's what I always use for boiling anything.

                                                                                            1. If I need to boil a pot of water for anything, the water in that pot comes from the Hot tap.

                                                                                              I save time.

                                                                                              Not a silly question.

                                                                                              1. The concern is lead in your water and reducing the amount of lead in the water you consume is important. Therefore, it's recommended that you always flush the tap and always start with cold.

                                                                                                I grew up in a house with hard water where the hot water was softened with salt, so we never used hot water to cook. Turns out this was a good habit for me to form!

                                                                                                If you want the pot to boil faster, cover it with a lid, but use cold water for health and taste.