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Dec 30, 2008 06:12 AM

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.


            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:

                                  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.