# Hot Water For Hygiene **URL:** \ **Category:** Factual Questions\ **Created:** [June 11, 2004, 10:01am UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791 "2004-06-11T10:01:31Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![talkvegas](https://avatars.discourse-cdn.com/v4/letter/t/bc8723/32.png) [@talkvegas](https://boards.straightdope.com/u/talkvegas)\ **Post date:** [June 11, 2004, 10:01am UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/1 "2004-06-11T10:01:31Z")
A friend of mine says his workplace has had a hot water heater broken for over a month. The company refuses to fix it. My friend claims hot water should be provided in the rest rooms and clean up areas for personal cleaning. The boss man says that the cleaning and sanitization comes from the soap, and that water temperature is for comfort only. Can the company really ignore the lack of hot water and is a warmer water temperature really just a convenience item when it comes to washing your face and hands? ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [June 11, 2004, 10:51am UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/2 "2004-06-11T10:51:10Z")
Short answer: hot water is better than cold [http://www.straightdope.com/mailbag/msoapwater.html](http://www.straightdope.com/mailbag/msoapwater.html) ---
**Author:** ![MrFantsyPants](https://avatars.discourse-cdn.com/v4/letter/m/7ba0ec/32.png) [@MrFantsyPants](https://boards.straightdope.com/u/MrFantsyPants)\ **Post date:** [June 11, 2004, 11:24am UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/3 "2004-06-11T11:24:32Z")
> [@talkvegas](#): > > Can the company really ignore the lack of hot water and is a warmer water temperature really just a convenience item when it comes to washing your face and hands? Tell him to wash his dishes in cold water then get back to you. He’s full of it. ---
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [June 11, 2004, 12:23pm UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/4 "2004-06-11T12:23:29Z")
Unless one’s hands are REALLY grimey, cold water should do fine for hand washing. Personal cleaning? Does this company have showers? Or do you mean like tupperware containers for lunch or something. Cold water should be fine for dishwashing and cleaning hands, but hot water would be better. I believe the reason why hot water is better is because it imparts thermal energy to the dirt and soap. the detergent molecules are moving more vigoriously and thus are more likely to capture some dirt molecules into their little micelle of hygeinc doom. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [June 11, 2004, 12:46pm UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/5 "2004-06-11T12:46:39Z")
Hot water also melts oily substances. Try running a knife with butter on it under cold water, then hot water, the hot definitely works better. ---
**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\ **Post date:** [June 11, 2004, 1:27pm UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/6 "2004-06-11T13:27:57Z")
> [@Harmonix](#): > > I believe the reason why hot water is better is because it imparts thermal energy to the dirt and soap. the detergent molecules are moving more vigoriously and thus are more likely to capture some dirt molecules into their little micelle of hygeinc doom. Sounds like scientific reasoning, so let’s see how big this difference might be: How much greater is the thermal enegy in 40[sup]o[/sup]C water, compared with 10[sup]o[/sup]C? As the thermal energy is proportional to the absolute temperature, that is easily seen by comparing 313K and 283K, which is about 10%. Clearly not enough to make much of a difference. > [@1920s Style "Death Ray"](#): > > Hot water also melts oily substances. Try running a knife with butter on it under cold water, then hot water, the hot definitely works better. Much more likelly. But I believe that there’s another effect as well. The solubility of most solids (as opposed to gasses!) increases with increasing temperature. Unfortunatelly I have no data on the solubility of grime versus temperature, but if any dopers have such tables, please post them! It’s also worth noting that the viscosity of water decreases noticably as the temperature increases. I don’t think this effect is great enough to cause any measurable difference when washing up though. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [June 12, 2004, 5:16am UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/7 "2004-06-12T05:16:08Z")
> [@MrFantsyPants](#): > > Tell him to wash his dishes in cold water then get back to you. No, don’t tell _him_ anything. Clearly, he wouldn’t listen anyway. Tell your local health inspector. Or the nearest office of OSHA. Or your Union Steward. Or the local TV station’s Investigative Reporter (especially during sweeps week). Or even try telling your boss’s boss (and mention how embarrassing it would be for the company if “somebody” were to tell all these other people). ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [June 12, 2004, 7:33am UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/8 "2004-06-12T07:33:20Z")
> [@Popup](#): > > Sounds like scientific reasoning, so let’s see how big this difference might be: How much greater is the thermal enegy in 40[sup]o[/sup]C water, compared with 10[sup]o[/sup]C? As the thermal energy is proportional to the absolute temperature, that is easily seen by comparing 313K and 283K, which is about 10%. Clearly not enough to make much of a difference. But the rate and amount of energy transferrence is related to the temperature differential. Given that 10C water is likely to be colder than the detergent, it will cool things down while the 40C water will heat things up. ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [June 12, 2004, 12:49pm UTC](https://boards.straightdope.com/t/hot-water-for-hygiene/249791/9 "2004-06-12T12:49:02Z")
Also, from this factsheet - [Washing Away Misconceptions About Gloves and Handwashing](http://www.rce.rutgers.edu/pubs/pdfs/fs991.pdf) (PDF!) > [@](#): > > Myth: The hotter the water you use for handwashing, the > better. > > Fact: In the past the Food and Drug Administration has > recommended that water temperature be 120°F for > handwashing. Recently they have changed their > recommendation 105°F ([http://vm.cfsan.fda](http://vm.cfsan.fda). > gov). There is no research to prove that higher > temperatures improve handwashing (18). > Handwashing water is not hot enough to kill > bacteria. However, hotter water is more likely to > cause excessive drying of the skin. It is harder to > remove bacteria from dry skin because of extra > cracks and grooves, and dry skin can make > handwashing painful (14). As a rule, the best > temperature to wash hands is the warmest temperature > that you find comfortable.