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Washing in "hot" water

greygarious Dec 23, 2009 10:00 AM

I suspect that we put more faith in the germ-killing ability of hot water than we should. Is the maximum temperature we can tolerate on our skin while washing our hands or foodstuffs or dishes hot enough to disinfect? It seems far more likely that it's the water, soap, and friction that do the job.

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  1. n
    nkeane RE: greygarious Dec 23, 2009 10:28 AM

    You're absolutely right. Hot water that you can stick your hand in and pull it back with skin still on it, is too cold to kill germs, for the most part. That being said, the warm water plus soap help dissolve the grease and thereby flush them away. I have heard that the most effective way to (hand)wash dishes is to wash in warm soapy water but rinse in cool, and let air dry. I believe the thinking is that the cool water promotes the growth of whatever bacteria are left behind(and there definitely are some left behind)less than the warm water, and air drying introduces less than then a towel(no matter how clean you think that towel is).

    I for one, will continue to jam 2 day old crusted lasagna pans in the dishwasher, set it to "pots&pans" and go blissfully on my way, *knowing*:-) I am 100% protected(should this be in the "magic house" thread?lol)

    4 Replies
    1. re: nkeane
      greygarious RE: nkeane Dec 23, 2009 10:43 AM

      Check your 5th sentence - I don't think you meant to write that cool water promotes bacterial growth.

      Edit: Oops - shaogo is right; never mind!

      1. re: greygarious
        shaogo RE: greygarious Dec 23, 2009 11:06 AM

        I read that, too. Read the sentence again, though. at the end of a parenthesis there's the all-important "less" The essence: cool water promotes ... *less* than the warm water...

        On-topic: it's nuts to burn oneself. To disinfect hands, the water would turn hands bright red and burnt in no time. The combination of soap, warm water and washing time are the three factors that disinfect hands. That's easier said than done, however, or should I say done but with a price. I work in a restaurant. I must wash my hands at least once or twice an hour, going from handling money to food to cleaning etc. I don't normally have a dry skin problem, but my hands are bone-dry despite use of lotions (corn-huskers lotion is great, though) and the skin's starting to split in places. It hurts.

        1. re: shaogo
          soupkitten RE: shaogo Dec 23, 2009 11:56 AM

          try plain olive oil-- it's foodsafe ;-P i'm greased up constantly this time of year, but it's a trick to do it lightly enough that knives etc aren't slipping out of your hands.

          just a note that restaurant dishwashing systems (mechanical) go to temps of 180 and above (kills germs, bacteria, etc), and by-hand (3 sink system) have a separate sanitizing soak followed by air-drying, after the initial soap and rinse. it's a little weird to do dishes at home, they just don't seem clean to me w/out the sanitizing rinse.

          1. re: soupkitten
            shaogo RE: soupkitten Dec 23, 2009 03:15 PM

            Thanks, soupkitten! Indeed, I'll try the olive oil. It never occurred to me. There're many times I'll use my hands to spread olive oil on something, but that's just when I'm cooking for myself. I spend a lot of time working the bar at our place, and I fear that even if I have the tiniest bit of oil on my hands, I'll leave fingerprints on the glasses. Who knows, maybe I'll get used to using it a bit and washing off my fingers only.

            I'm also with you about the dishwasher. Our home dishwasher is extremely energy-efficient and I think that's why it takes longer than home dishwashers I'd become used to. Oh, what a luxury to have the restaurant dishwasher turn oily, greasy, caked-on saucy plates into squeaky-clean mirrors -- and in under a minute!

    2. c
      chococat RE: greygarious Dec 23, 2009 11:50 AM

      I don't know if this is true or not, but a friend told me once that, from a foodservice safety perspective, the reason that warm (not necessarily hot) water is required for handwashing is because people won't tolerate the cold water for long enough to do a thorough hand washing.

      1. KaimukiMan RE: greygarious Dec 23, 2009 02:48 PM

        I grew up with the hot wash water in the sink, and a cool rinse in the other bowl. I have found that here in Hawaii a lot of people don't fill the sink at all, they keep the warm water running rinse first, then wipe/scrub with a soapy sponge and then rinse again. They dont think that having things soak in a warm batch of water gets things clean and is just a breeding place for germs.

        3 Replies
        1. re: KaimukiMan
          taos RE: KaimukiMan Dec 24, 2009 04:10 PM

          I don't know if this has anything to do with Hawaii. live about as far away from Hawaii as you can get and still be in the United States and this is how I wash dishes.

          1. re: KaimukiMan
            c oliver RE: KaimukiMan Dec 26, 2009 02:46 PM

            I think you might get arrested in CA for leaving the water running while you wash your dishes :) Or brush your teeth or shave. Naughty water wasters all.

            1. re: KaimukiMan
              kubasd RE: KaimukiMan Dec 26, 2009 03:24 PM

              i live in ct and this is how i wash dishes...

            2. OCEllen RE: greygarious Dec 23, 2009 03:37 PM

              Gloves - I wear them always when washing dishes and used pure hot water as it comes from the tap.

              22 Replies
              1. re: OCEllen
                KaimukiMan RE: OCEllen Dec 24, 2009 01:31 PM

                The water coming out of your water heater should not be more than 140 degrees in order to avoid scalding (yes, it is a law.) That is not hot enough to kill anything.

                1. re: KaimukiMan
                  taos RE: KaimukiMan Dec 24, 2009 04:54 PM

                  So if I crank my hot water heater up so the water coming out of it is higher than 140 degrees I'm breaking the law? Is it a criminal violation or just like a parking ticket? Will I have to do jail time? Will it be on my permanent record forever? What if the water heater is just set that hot but no one ever touches it?

                  1. re: taos
                    Popkin RE: taos Dec 24, 2009 06:51 PM

                    It might be one of those things.... The installer has to set it no higher than 140. After that I'd think it's a case of "well, it's your water heater". Though I suspect that were you to sell your house, you might be obligated to lower the temp.

                    *disclaimer: pulling this from memory, from a few little blurbs. So don't take my word for it :P

                    1. re: taos
                      KaimukiMan RE: taos Dec 25, 2009 09:17 AM

                      Before this change (sometime in the 80's I beleive) hot water heaters were typicaly set to 160 or so, and resulted in many cases of people being scalded.

                      If you choose to set your's higher just hope no one visitng ever gets scalded, including any tradespeople, or you could have a nice fat lawsuit to deal with. I don't like the government interfering inside my home either, but most safety laws do have some basis in reality. I wouldn't advise you to take the railings off your staircase, or put plain glass in a sliding glass door instead of safety glass... but people do these things too.

                      1. re: KaimukiMan
                        johnb RE: KaimukiMan Dec 25, 2009 06:46 PM

                        Kamukiman is right IMO. It is really not good to set your water heater much higher than 120. At temperatures around 150 or so, there is a really big risk that eventually somebody will be scalded, perhaps badly, and if it happens to be, say, your 2 year old niece who was visiting you will feel really bad about that for the rest of your life, not to mention the effect on her. Don't take that risk.

                        If you hand wash your dishes in soapy 120-130 water, they won't be "sanitized", but the mechanical process of getting all the residue off is really good enough. Nobody is likely to get sick from them after that. If you insist on sanitizing, there are many home dishwashers that have sanitizing cycles (NSF rated) that will do the job--they have their own built-in heaters. That's probably your best bet.

                        1. re: johnb
                          taos RE: johnb Dec 26, 2009 07:22 AM

                          Here's the rub. I don't have a dishwasher and I can't put one in. So I crank the hot water heater up as high as I can stand in an effort get the dishes clean. i'm not sure what the temp is. There's no thermometer on the heater, but it seems pretty hot.

                          1. re: taos
                            greygarious RE: taos Dec 26, 2009 08:03 AM

                            Since the temperature required to kill bacteria with heat alone would burn your hands, you are achieving nothing but a higher energy bill. Comfortably warm water is enough to soften congealed fat, which is then dissolved and removed by soap and elbow grease. Germs that aren't washed and rinsed away are killed by air-drying. Dishwashers were unheard of 50 years ago and most of the world still doesn't use them and nevertheless isn't succumbing to the germs on their teacups.

                            1. re: greygarious
                              taos RE: greygarious Dec 27, 2009 09:16 AM

                              What if I: 1) let the water run on the dishes without my hands on them? 2) wear gloves?

                              By the way, your statement that "dishwashers were not unheard of 50 years ago" is false. My parents had one in their suburban tract house that was built in 1956. I believe it came as standard equipment with the house.

                              Here's an article on the history of the dishwasher.

                              It confirms that the dishwasher was invented in the mid 19th century and installed mostly in commercial establishments until the home dishwasher became common place a century later.

                              I also worked as a commercial dishwasher at a large hotel in the 1980s. We used very hot water and wore thick rubber gloves so we wouldn't scald our hands.

                              In any case, the reason I use hot water, isn't because I'm hoping to totally santize the dishes. My dishes don't really need sanitizing. They're are too many free-flating germs around the house anyway. If I wanted sanitizing, I'd use bleach. I use hot water to get the grease off quickly and easily.

                              1. re: taos
                                greygarious RE: taos Dec 27, 2009 10:11 AM

                                I was a child in the 1950's on Long Island. Most of the houses in the neighborhood were built 10-20 years earlier, without them, and nobody had installed one. There was an occasional kitchen sink with an after-market disposal but even that was rare. So I'll amend that time frame to say that 50 years ago unless you had a newly built home, you were unlikely to have a dishwasher. Mine was built 40 years ago and has one that I never use.

                                1. re: taos
                                  c oliver RE: taos Dec 27, 2009 11:38 AM

                                  Your last sentence is exactly why I do it. One of SIL's washes with tepid water. When they visit us, I wind up rewashing some things, esp. the wine glasses that can't go in the DW. (I dont let him SEE me do this.)

                              2. re: taos
                                alanbarnes RE: taos Dec 26, 2009 11:14 AM

                                You simply can't sanitize dishes by hand-washing them. As others have noted, the temps required would nearly immediately cause blistering burns on your hands.

                                If killing the germs on the dishes is that important to you, you can wash, rinse, and then sanitize them in a diluted bleach solution. Or pop 'em in a 175F oven for half an hour.

                                1. re: alanbarnes
                                  Steve RE: alanbarnes Dec 26, 2009 02:39 PM

                                  I don't know what you mean exactly by sanitize. It doesn't seem to be a major health risk to wash dishes by hand.

                                  1. re: Steve
                                    alanbarnes RE: Steve Dec 26, 2009 03:28 PM

                                    Sanitize - to make sanitary. To kill any microorganisms that may be present. Washing dishes with soap and warm water makes them clean, but it doesn't sanitize them. There is still the possibility that germs are present on the dish.

                                    Do I worry about this in my kitchen at home? Not a bit. But this thread is about killing germs.

                                    In commercial kitchens, health codes require that dishes not only be clean, but sanitary. This is typically accomplished either with heat (a commercial dishwasher gets up to about 180F) or with oxidizing agents.

                                    Ever notice the little 3-compartment sinks on food carts? They're required because one bowl holds the wash water, the second holds the rinse water, and the third holds a sanitizer.

                                    @johnb: I'm not saying that the dishes in a home kitchen need to be sanitized. I'm just saying that hot water isn't going to do the trick. And if somebody wants or needs to up the ante with regard to kitchen hygiene (for example, if somebody in the house is has a serious communicable disease or is immunocompromised), sanitizing dishes is one of many steps that should be taken, and it isn't an overwhelmingly difficult task.

                                  2. re: alanbarnes
                                    johnb RE: alanbarnes Dec 26, 2009 02:40 PM

                                    Of course it's also true that even if you do sanitize your dishes, by whatever method, there are so many other non-sanitary things around that are getting on your food (your hands for starters) that sanitizing them isn't going to accomplish anything anyway. It's akin to using a bulletproof vest to protect yourself from a gas attack.

                                    1. re: alanbarnes
                                      chef chicklet RE: alanbarnes Dec 26, 2009 04:32 PM

                                      What about the mw, will that do it?

                                      1. re: chef chicklet
                                        alanbarnes RE: chef chicklet Dec 26, 2009 04:45 PM

                                        The microwave is an effective way to sanitize damp things - kitchen sponges, dishrags, etc. - but I'm not sure how it would work with dishes. The reason it's so effective with a damp sponge is that the water in the sponge gets the whole thing so hot that bacteria can't survive.

                                        But I don't know whether the microwaves could reliably overheat the moisture inside each individual bacterium. And if you're microwaving dry dishes, you're eventually going to roast your magnetron because there's not much if anything to absorb the waves. Never mind the potential problems with any metallic trim or paints...

                                        1. re: chef chicklet
                                          greygarious RE: chef chicklet Dec 26, 2009 06:08 PM

                                          Use a 1:28 bleach to water solution if you're that particular. For that matter, you might as well add bleach to your tap water. Ever see what the inside of an old water main looks like? Lately my tap water tastes of bleach - this happens periodically, when the town supply gets compromised. Adding a little bleach to the drinking water in kennels and other animal housing is also safe, and standard in many operations.

                                          1. re: greygarious
                                            c oliver RE: greygarious Dec 26, 2009 06:12 PM

                                            Just a higher level of chlorine.

                                            1. re: greygarious
                                              KTinNYC RE: greygarious Dec 27, 2009 10:26 AM

                                              What are people doing in their homes that they need to chlorinate their dishes? It's a good suggestion for the paranoid or those with extreme immune deficiencies but for the rest of us this is overkill.

                                              1. re: KTinNYC
                                                greygarious RE: KTinNYC Dec 27, 2009 11:04 AM

                                                I was responding to chef chicklet's quest for sterility - me, I fill the dishpan,
                                                add Palmolive detergent and hot tap water, let' em soak till the water is warm, then use a dishcloth, rinse under a thin stream of cold water, and into the dishrack to air-dry. The pre-wash in this house is 3 greyhounds and I am quite sure that on occasion I've mistaken dishes they "cleaned" for ones I've washed. Paranoid I'm not.

                                                1. re: greygarious
                                                  KTinNYC RE: greygarious Dec 27, 2009 11:08 AM

                                                  Yes, I know you were just answering a question. I certainly didn't think you were doing this on a regular basis in your home!

                                                  1. re: greygarious
                                                    c oliver RE: greygarious Dec 27, 2009 11:40 AM

                                                    LOL, gg. For years we never let my MIL know that the dogs (then Labs) were licking the plates. But now she loves the dogs more than us so it's okay :) And that way we're not wasting either - ah, how these threads weave, eh?

                              3. s
                                Steve RE: greygarious Dec 23, 2009 04:17 PM

                                I am not aware of any warm water standard for killing bacteria. When I go camping, all the dishes get washed in cold water all the time. Same thing at primitive cabins. In fact, I would say that the cups and dishes at most primitive cabins never get washed in anything but cold water.

                                1. maria lorraine RE: greygarious Dec 24, 2009 03:34 PM

                                  The effectiveness of hot water has been studied extensively for its germ-killing potential, and 180 degrees F. seems to be the magic number. Lots of lab experiments were done that tested various pathogens -- listeria, e. coli, etc. -- and at what temp those pathogens were killed. Studies are available online if you search.

                                  This came even more to light when a few years ago Hobart (the maker of commercial dishwashing equipment) not so secretly funded a "study" that said hot water was not required -- warm water would suffice -- but only if there was a final sanitizing compartment wherein the dishes were submerged for a certain amount of time. The kicker is that Hobart manufactures the dishwasher with the special sanitation sink and sells all the chemicals needed for that final sanitation procedure. It was a sham study, of course, but what came to light yet again was the temperature at which pathogens die. This applies to a restaurant situation however.

                                  On the homefront, I never worry about the dishes I wash by hand in less than 180 degree F water. I use the hottest water that I can stand, soap, and a scrubber. The mechanical action of scrubbing -- just like when washing one's hands -- does make a difference in bacterial content.

                                  1 Reply
                                  1. re: maria lorraine
                                    Will Owen RE: maria lorraine Jan 17, 2010 03:30 PM

                                    I put in a "pearl-diving" stint in a small cafe when I was in school - this was in California - and the washing was all done strictly by hand. I had three sinks: wash, rinse, and disinfect. The washed dishes went into the rinse water, and then into the disinfectant solution. When we were rushed they'd go directly into service, but most of the time they'd get a spray-down first, though the disinfectant solution was not as aromatic as regular bleach. The water had to be replenished frequently, as it needed to stay above a certain temperature - I don't remember what that was, but it was REALLY hot. I was supposed to wear gloves, but I was young at the time and both immortal and bulletproof ;-)

                                  2. Kajikit RE: greygarious Dec 29, 2009 08:29 PM

                                    Hot water does a much better job of dissolving/removing grease and grime than cold. The detergent does the disinfecting. Oh, and really hot water rinses dishes more sparkly clean.

                                    1. l
                                      lgss RE: greygarious Jan 17, 2010 12:41 PM

                                      When any of us was sick my mother would boil water on the stove and put the flatware in it and dip rims of drinking glasses in it. Don't know how much it helped. When we were younger we had "name" (at one time they had the plastic labels one could make with a device that created raised letters) glasses where everyone had a specific color and always used the same one for meals. Unfortunately, the "name" glasses were aluminum.

                                      1. d
                                        dagwood RE: greygarious Jan 17, 2010 04:39 PM

                                        It was always my understanding, (as well as anectodedly-proven in-practice), that rinsing in cold water provides a cleaner rinse.

                                        That said, I practice this in-home only. When I worked in a commercial setting the rinse water (prior to the disinfectant) was in the hottest water one's hands could tolerate.

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