# How hot should I set my hot water heater? **URL:** \ **Category:** Factual Questions\ **Created:** [June 4, 2004, 3:07am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572 "2004-06-04T03:07:39Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Mahaloth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mahaloth/32/1079_2.png) [@Mahaloth](https://boards.straightdope.com/u/Mahaloth)\ **Post date:** [June 4, 2004, 3:07am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/1 "2004-06-04T03:07:39Z")
Pretty straight forward question. What is the normal temperature to set the hot water heater in one’s home. I just moved and my new heater is defaulted to 70 Degrees Celcius. What do you suggest? Tell me either Fahrenheit or Celcius, but tell me which one, please. Thanks! ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [June 4, 2004, 3:12am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/2 "2004-06-04T03:12:17Z")
I _belive_ 120 degrees Fahrenheit is commonly accepted temp. ---
**Author:** ![Papermache\_Prince](https://avatars.discourse-cdn.com/v4/letter/p/f05b48/32.png) [@Papermache\_Prince](https://boards.straightdope.com/u/Papermache_Prince)\ **Post date:** [June 4, 2004, 3:17am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/3 "2004-06-04T03:17:05Z")
According to this United States Consumer Product Safety Commission [pag](http://www.cpsc.gov/cpscpub/pubs/5098.html). > [@](#): > > The CPSC notes that a thermostat setting of 120 degrees Fahrenheit (49 degrees Celsius) may be necessary for residential water heaters to reduce or eliminate the risk of most tap water scald injuries . . .Most adults will suffer third-degree burns if exposed to 150 degree water for two seconds. Burns will also occur with a six-second exposure to 140 degree water or with a thirty second exposure to 130 degree water. Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns… Celcius at 70 degrees = Fahrenheit at 158 degrees, so that’s too damn hot by these standards. ---
**Author:** ![Toddly](https://avatars.discourse-cdn.com/v4/letter/t/22d042/32.png) [@Toddly](https://boards.straightdope.com/u/Toddly)\ **Post date:** [June 4, 2004, 3:23am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/4 "2004-06-04T03:23:51Z")
I also agree with the 120 degree temperature. Thats what we set ours at and it is plenty hot. 70 C is much to hot. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [June 4, 2004, 3:36am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/5 "2004-06-04T03:36:18Z")
You should be aware that (at least in Massachusetts in the 1980s and early 1990s, when I built/renovated bathrooms in my house) temperature limiting devices were required for bathtubs, but not sinks [especially single fixture units). These were mixing valves that automatically metered some cold water into the hot, even when the hot water was on “full”. These were adjustable at the time of installion, but you might have to remove the entire fixture or open the wall a bit to change the setting. You probably don’t have this on your faucets however. So you have a choice: a less than satisfyingly hot bath, ot a potentially scalding faucet. In our house, we opted for hotter baths, but we have no small children anymore. ---
**Author:** ![Carnac\_the\_Magnificent](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Carnac\_the\_Magnificent](https://boards.straightdope.com/u/Carnac_the_Magnificent)\ **Post date:** [June 4, 2004, 3:42am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/6 "2004-06-04T03:42:14Z")
Some sources claim that lower temperatures raise the risk of Legionnaire’s Disease. Not so according to several sources, among this one: "Most importantly, more than 15 years of experience with lower heater temperatures in the U.S. has not resulted in an increase in Legionnaire’s Disease in non-institutional settings. Through regulations at the state level and then a voluntary change in industry standards nation wide, new hot water heaters in the U.S. have been factory-set at a maximum of 120 to 125 degrees Fahrenheit (49 to 52 degrees Celsius) since the late 1980s. People with certain medical conditions should check with their doctor before reducing the temperature of the water in their homes. These conditions include a weak immune system, lung and respiratory problems, or organ transplants. People with these conditions should keep their water heaters at 60 degrees Celsius to reduce the risk of bacteria in their water. Anti-scald devices on hot water taps or in water lines can provide burn protection in these homes. Most families, however, can safely lower their water temperature without concern for other health risks." [http://216.239.41.104/search?q=cache:dcH55brfsLcJ:www.safekidscanada.ca/ENGLISH/Safety\_Tips/ST\_Protect\_kids\_from\_scalds.html+"hot+water+heater"+legionnaire's&hl=en](http://216.239.41.104/search?q=cache:dcH55brfsLcJ:www.safekidscanada.ca/ENGLISH/Safety_Tips/ST_Protect_kids_from_scalds.html+%22hot+water+heater%22+legionnaire%27s&hl=en) ---
**Author:** ![mhendo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mhendo/32/3159_2.png) [@mhendo](https://boards.straightdope.com/u/mhendo)\ **Post date:** [June 4, 2004, 5:12am UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/7 "2004-06-04T05:12:55Z")
Our water heater doesn’t have a temperature scale on the dial, only the words “vacation,” “warm,” and “hot.” Hot is way too hot, even for someone like me who likes to have nice hot water available. I have it set half way between warm and hot, which is too hot to leave your hands underneath for more than a second, but which isn’t so hot that it scalds immediately on contact. I imagine it’s still hotter than most people would recommend, but there’s nothing i hate more than trying to wash dishes with lukewarm water. ---
**Author:** ![JimMacMillan](https://avatars.discourse-cdn.com/v4/letter/j/7bcc69/32.png) [@JimMacMillan](https://boards.straightdope.com/u/JimMacMillan)\ **Post date:** [June 4, 2004, 3:31pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/8 "2004-06-04T15:31:04Z")
I never understood why one would want to heat hot water 🙂 Jim ---
**Author:** ![Dung\_Beetle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dung_beetle/32/7945_2.png) [@Dung\_Beetle](https://boards.straightdope.com/u/Dung_Beetle)\ **Post date:** [June 4, 2004, 3:43pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/9 "2004-06-04T15:43:40Z")
Damn you,\*\* Jim\*\*, you beat me to it! 🙂 ---
**Author:** ![The\_Controvert](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)\ **Post date:** [June 4, 2004, 6:57pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/10 "2004-06-04T18:57:14Z")
You heat hot water to make it hott_er_. Or am I throwing cold water on your joke? ---
**Author:** ![RAWDuke](https://avatars.discourse-cdn.com/v4/letter/r/71e660/32.png) [@RAWDuke](https://boards.straightdope.com/u/RAWDuke)\ **Post date:** [June 4, 2004, 7:14pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/11 "2004-06-04T19:14:54Z")
Personally, I set my COLD water heater to hot. 😃 ---
**Author:** ![1010011010](https://avatars.discourse-cdn.com/v4/letter/1/ea666f/32.png) [@1010011010](https://boards.straightdope.com/u/1010011010)\ **Post date:** [June 4, 2004, 9:12pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/12 "2004-06-04T21:12:21Z")
> [@JimMacMillan](#): > > I never understood why one would want to heat hot water. So they could mix it with a larger volume of relatively colder water, and thus yeild a larger volume of warm water than would be possible with unheated hot water. Practically speaking, longer showers. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [June 4, 2004, 10:43pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/13 "2004-06-04T22:43:58Z")
Use the trial and error method. Set it for a certain temp, if it works out try a little colder, if it doesn’t try a little hotter. Eventually you should find the Goldilocks temp. Also note that your water might be hot enough for you (and your 3 bears) but not enough for your dishwasher. So if your glasses don’t come out crystal clear, you don’t need Cascade, just a warmer setting. ---
**Author:** ![Early\_Out](https://avatars.discourse-cdn.com/v4/letter/e/6f9a4e/32.png) [@Early\_Out](https://boards.straightdope.com/u/Early_Out)\ **Post date:** [June 4, 2004, 11:39pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/14 "2004-06-04T23:39:57Z")
> [@kanicbird](#): > > Also note that your water might be hot enough for you (and your 3 bears) but not enough for your dishwasher. So if your glasses don’t come out crystal clear, you don’t need Cascade, just a warmer setting. Whether this a problem or not depends upon whether your dishwasher will boost the temperature of the water, or just uses it as it comes from the water heater. For good results washing dishes, you need water that’s at least 140 degrees, I believe. If your water heater is set at 120, it’s not a problem if your dishwasher will fire up its heating coils and raise the temperature. (And **1010011010** , I think you’ve missed the joke. There’s no such thing as a “hot water heater.” If the water’s hot, it doesn’t need to be heated. There’s only a “cold water heater,” or, simply, a “water heater.”) ---
**Author:** ![Mahaloth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mahaloth/32/1079_2.png) [@Mahaloth](https://boards.straightdope.com/u/Mahaloth)\ **Post date:** [June 7, 2004, 2:29pm UTC](https://boards.straightdope.com/t/how-hot-should-i-set-my-hot-water-heater/248572/15 "2004-06-07T14:29:56Z")
Well, I’ve left it on 70 Degrees Celcius, and it seem just fine. That was the default temperature and it seems to work. The hot is very hot, but I can get warm water when I have the faucets in the middle.