# How hot does water have to be to kill germs? **URL:** \ **Category:** Factual Questions\ **Created:** [August 30, 2012, 9:51pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192 "2012-08-30T21:51:56Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![ThelmaLou](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thelmalou/32/390_2.png) [@ThelmaLou](https://boards.straightdope.com/u/ThelmaLou)\ **Post date:** [August 30, 2012, 9:51pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/1 "2012-08-30T21:51:56Z")
If I rinse my toothbrush or my Clarisonic (face cleaning brush thingie) in hot tap water for a good long time, like 20 seconds or so, am I killing any germs? ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [August 30, 2012, 10:06pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/2 "2012-08-30T22:06:36Z")
How many germs do you want dead? If you want it absolutely sterile, you need to get a fair bit above boiling, which means high pressure steam or an autoclave. Ordinary boiling water will kill the vast majority of germs, but a few hardy spores will survive. Very hot water will still kill most of the germs – 160° F ought to suffice, since that temperature is good enough for stuff you eat. The 120-140 from your hot water tap won’t kill much at all. But why worry? No matter how nasty your toothbrush is, it won’t have as many germs as are already living in your mouth. Same with you face brush thing. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [August 30, 2012, 10:08pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/3 "2012-08-30T22:08:38Z")
toothbrushes can deteriorate faster with the exposure to heat (so i’ve heard). hot tap water wouldn’t do much different than cold water. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [August 30, 2012, 10:29pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/4 "2012-08-30T22:29:58Z")
You’ll remove more germs just by washing them off; just hold it under the full-open tap for a few seconds and if it looks clean and doesn’t smell like toothpaste, it should be clean enough (and [don’t store it in the open near the toilet](http://serendip.brynmawr.edu/exchange/node/1839) if you are really concerned about germs, I keep mine on the bedroom dresser). ---
**Author:** ![ThelmaLou](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thelmalou/32/390_2.png) [@ThelmaLou](https://boards.straightdope.com/u/ThelmaLou)\ **Post date:** [August 30, 2012, 11:31pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/5 "2012-08-30T23:31:30Z")
> [@lazybratsche](#): > > How many germs do you want dead? I don’t know. ---
**Author:** ![The\_Surb](https://avatars.discourse-cdn.com/v4/letter/t/ce73a5/32.png) [@The\_Surb](https://boards.straightdope.com/u/The_Surb)\ **Post date:** [August 31, 2012, 12:57am UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/6 "2012-08-31T00:57:12Z")
Health dept. regulations in Michigan in 1987 required water to be 170°F to sterilize kitchen utensils. ---
**Author:** ![ThelmaLou](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thelmalou/32/390_2.png) [@ThelmaLou](https://boards.straightdope.com/u/ThelmaLou)\ **Post date:** [August 31, 2012, 1:00am UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/7 "2012-08-31T01:00:37Z")
> [@The\_Surb](#): > > Health dept. regulations in Michigan in 1987 required water to be 170°F to sterilize kitchen utensils. Thanks. That’s helpful. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [August 31, 2012, 1:28am UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/8 "2012-08-31T01:28:52Z")
There’s also a time element. The hotter the water is, the quicker it kills. ---
**Author:** ![Baracus](https://avatars.discourse-cdn.com/v4/letter/b/2bfe46/32.png) [@Baracus](https://boards.straightdope.com/u/Baracus)\ **Post date:** [August 31, 2012, 12:59pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/9 "2012-08-31T12:59:02Z")
> [@The\_Surb](#): > > Health dept. regulations in Michigan in 1987 required water to be 170°F to sterilize kitchen utensils. Nitpick: That temperature will _sanitize_ the utensils, meaning reduce the microbial load down to safe, but not zero, levels. _Sterilization_ means the elimination of all organisms, which requires a temperature greater than 170ºF. ---
**Author:** ![ThelmaLou](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thelmalou/32/390_2.png) [@ThelmaLou](https://boards.straightdope.com/u/ThelmaLou)\ **Post date:** [August 31, 2012, 1:25pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/10 "2012-08-31T13:25:06Z")
> [@Baracus](#): > > Nitpick: That temperature will _sanitize_ the utensils, meaning reduce the microbial load down to safe, but not zero, levels. _Sterilization_ means the elimination of all organisms, which requires a temperature greater than 170ºF. Good nitpick. That’s why I keep you all on my staff. ---
**Author:** ![Perderabo](https://avatars.discourse-cdn.com/v4/letter/p/a183cd/32.png) [@Perderabo](https://boards.straightdope.com/u/Perderabo)\ **Post date:** [August 31, 2012, 2:36pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/11 "2012-08-31T14:36:11Z")
> [@lazybratsche](#): > > If you want it absolutely sterile, you need to get a fair bit above boiling, which means high pressure steam or an autoclave. nitpick: [Strain 121](http://en.wikipedia.org/wiki/Strain_121) can thrive in an autoclave. It’s not a threat to people, our bodies are to cold for it. But it freaks me out just the same. Prions aren’t germs or even alive. But if you had some prions on a surgical instrument you would probably want them removed. I’m not sure I would trust an autoclave to do that. ---
**Author:** ![Minnie\_Luna](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@Minnie\_Luna](https://boards.straightdope.com/u/Minnie_Luna)\ **Post date:** [August 31, 2012, 4:11pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/12 "2012-08-31T16:11:53Z")
> [@Perderabo](#): > > nitpick: [Strain 121](http://en.wikipedia.org/wiki/Strain_121) can thrive in an autoclave. It’s not a threat to people, our bodies are to cold for it. But it freaks me out just the same. Prions aren’t germs or even alive. But if you had some prions on a surgical instrument you would probably want them removed. I’m not sure I would trust an autoclave to do that. Autoclaving does not fully inactivate prions, prions are not killed, but rendered inactive by chemical means combined with heat sterilization. I think bleach for 60 min will do it, followed by a cycle in the autoclave. I don’t remember the exact procedure for surgical instruments that come in contact with nervous tissue, but you need both. ---
**Author:** ![ThelmaLou](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thelmalou/32/390_2.png) [@ThelmaLou](https://boards.straightdope.com/u/ThelmaLou)\ **Post date:** [August 31, 2012, 10:18pm UTC](https://boards.straightdope.com/t/how-hot-does-water-have-to-be-to-kill-germs/633192/13 "2012-08-31T22:18:40Z")
> [@Minnie\_Luna](#): > > I don’t remember the exact procedure for surgical instruments that come in contact with nervous tissue, but you need both. My tissues get nervous at the very \*thought \*of contact with surgical instruments.