Water heater temp's, what's the ideal Min – Max?

revvinkevin · Jul 7, 2014

Six months or so ago I installed a new water heater but didn't really dial in the temp or even check it until today. At the kitchen faucet it's 150°. I know that's great for the dishwasher, however I think it might be a bit too hot otherwise.

So my question is: where should the water heater temp be set?

Or, what temp do you have yours set for?

Thanks so much in advance!
Kevin

whirlcool · Jul 7, 2014

On our Bradford White gas unit there is a red mark at 140F which I take indicates a normal setting and that's where we keep ours. We sometimes turn it up to 160F for laundry days. But then we turn it back to 140F when laundry is done.

I know a lot of people keep theirs set theirs at 120F. They do this so they can use full hot and not burn their fingers. Also parents who have small kids do this as a safety procedure.

Then you have your people who keep theirs set at "Vacation". The water is slightly warmer than room temperature. I think they do it because they are cheap. But I read an article somewhere that said this could be a dangerous practice because water in a water tank under 120F can pick up dangerous bacteria and heat at 120F will eliminate it. My nutty sister does this and when you take a shower at her place you have the water set to full hot and the water is just barely warm enough to be comfortable in. The nutty woman down the street from us does it because she thinks that if you have it set "too high" the hot water tank will flood your house with Carbon Monoxide fumes.

So I would think that 140F would be considered normal.

The link leads to an article that mentions bacteria in home water heaters.

http://www.treehugger.com/green-food/is-it-safe-to-turn-down-your-water-heater-temperature.html

washer111 · Jul 7, 2014

With a Solar-Water-Heater - there is no minimum or maximum! Anywhere from tap-cold to boiling, depending on the conditions.*1

The best solution is to temper the water to prevent scalding in the areas that need such protection. But honestly, I find that even 120ºF water is enough to produce steam and scald me - so how it "protects children" is beyond my comprehension. They always say to never bathe a baby at hotter than lukewarm - or else scalding occurs. So whats the difference?

Based on that article - water heaters hold probably be set to about 130º, to ensure Legionella is still being killed off. Perhaps mandate that, BUT, if people remembered to actually flush their water-heater tanks every year, then this probably wouldn't be an issue.

My advice: Set the water heater as cool as you feel safe in doing so. Perhaps engage in "prudent maintenance" to ensure your livelihood's protection.

If you are pressed for money - it might be worth considering upgrading your water heater, adding insulation or changing your usage habits to suit your utilities' usage plan. For example, Australians can (Make that COULD) purchase Electric water-heaters that have a full-tank element running off a timer for Off-Peak electric rates, and a smaller unit at the top of the tank for boosting during the day if the temperature dropped below a reasonable level.

*1:

Its actually expected/recommended by the manufacturer of our solar water heater to keep the electric or gas boosting element activated year-round - to ensure water of a minimum temperature of 140º - this is supposed to meet the Australian Standard, AS3498 that requires water heaters to have some means of eliminating Legionella growth. They must also be set no colder than 140º.

Personally, I think this is another example of overregulation and the "Nanny State" we live in. If people in the U.S. are using their water heaters at 120º or colder, without many headline issues - I think it is silly not provide the means to save energy. It is your life, after all.

We don't actually follow this recommendation, and I seriously hope other Aussies are doing the same. Energy already costs a fortune here - and the added burden isn't worth it. (We pay about $300 bi-monthly in the Winter for electricity. Thats going up another 2-3 c/kWh from July 1. Summer bills will easily reach $900)

arbilab · Jul 7, 2014

US water heaters ship set at 120F. Prolly cuz they could be sued for burns if set to 140 which dishwashers of course prefer. In short there is no ideal as long as you're paying to heat it. Higher tank temp, more heat is lost to radiation. If anyone in the house is likely to put their hand in tap hot, 120F is uncomfortable but not scalding in the time it takes to realize it's hot. Unless the person is insensitive to heat, blahblahblah.

As to legionella, will grow below 140-150 but pritdang unlikely to get in there from a chlorinated supply. Wellwater, deeper subject. Or catchment. How does the COLD tank not grow wildlife? Rainwater isn't sterile ya know.

How oh how did humans ever survive to reach an age where nannyments prohibit us from doing anything dangeroos (sic)?

beekeyknee · Jul 7, 2014

Ours is set as high as it will go. It fluctuates a bit when not used recently, so HOT it is.

appnut · Jul 7, 2014

Mine is set at 120. It's an electric Whirlpool SmartSaver. I remember hearing or reading somewhere that higher temperatures shorten the life of water heaters.

frigilux · Jul 7, 2014

My natural gas heater is set so water coming from the tap is around 142 degrees F. Probably hotter than needed---both dishwasher and washing machine have internal heaters---but old habits die hard, I guess.

Personally, 120 degrees as a max temp isn't hot enough. Were there little kids in the house, I'd think differently.

chachp · Jul 7, 2014

Between the Hot and Very Hot setting.

I have a Rheem Natural Gas water heater. It's about 6 months old. I have it set between the Hot and Very Hot setting and it comes out at about 130-135 at the kitchen faucet. That seems good for me to get a hot shower.

Both my Dishwasher and Washing Machine heat the water so I could get by with a lower setting but I like nice hot showers.

polkanut · Jul 7, 2014

Ours is set kind of in the middle @ roughly 130 degrees. It's a nice all-purpose temp for our needs.

DADoES · Jul 7, 2014

As discussed in previous discussions on water heaters, my tankless unit is set at 102°F for showering and "warm"-ish clothes washing. I raise it as needed for some tasks, but not for the dishwasher being as it has onboard heating. I occasionally *lower* it a little for a cooler shower such as after mowing the yard.

super32 · Jul 7, 2014

We are set at 130. I will push it up to 140 during the winter simply for showering. The dishwasher and washer have heaters so there really is no reason for us to go any higher.

daveamkrayoguy · Jul 7, 2014

We just got a new water heater, more than a month ago, so right now it's a bit of a battle to try to adjust the temperature control on it, so we don't freeze, or burn...

This is really only critical with the bathtub, (Isn't it always?!) but now our daughter wants to take her own showers, by herself...

So an awful lot of fine-tuning the Hot & Cold faucet controls is needed, as I reach into the tub, wetting my upper-extremities, soaking the bathroom outside of the tub, and all...!!!!

-- Dave

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xraytech · Jul 7, 2014

I had my mothers a Whirlpool set at the highest setting somewhere between 150-160.
Now I need to figure out how to change the temp on my water heater it's about a 2008 model, it seems to be set around 115-120 and I'd prefer 140-150 mostly for dish washing in the sink and laundry needs

jons1077 · Jul 7, 2014

120-140 degrees

We got a tankless water heater installed when we had the new furnace installed with natural gas. It allows for a range of 120-140 degrees. I tend to keep it at the 140 degrees mark because the dishwasher works better and the rinses are warmer in the washers.

rp2813 · Jul 7, 2014

Right around 130 here. That's hot enough to work with, and the Miele dishwasher has an on-board heater. Most dishwashers with heaters suggest a minimum setting of 120. For me, 130 gets most jobs done and probably evens things out for rinses in the Miele since the water heater is around 20' away, as the pipes run.

It makes no difference for the laundry. Having the heater set at 140 or 150 would only prompt the Affinity's auto-temp function to start mixing in cold water that much sooner during the fill. :-/

brisnat81 · Jul 7, 2014

Our Solar system is Tempered so that the hot water is limited to 120F

If we electrically boost the water temp, the maximum tank temperature goes up to 140F but the temp at the taps stays at 120F

During summer in the hot weather when there is lots of solar gain, the tank temp can get up as high as 170F, the TPR valve starts to open at 185F to let cold water in to cool the tank down. Again, the tempering valve keeps the tap temp to 120F.

I'm not sure why in the US they don't advocate Tempering valves more. That way you keep the tank hot enough to prevent legionella but you can still prevent scalding at the tap.

As a sidenote, any hotwater connected appliances in Australia advise that the hot water supply should not be higher than 140F

yogitunes · Jul 7, 2014

I have mine set at 160....the kids bathroom has tempering/anti-scald valves....

you have to consider, incoming temps, and demand times for keeping it that hot and available.....one or two persons is one thing....having a family and several machines hooked up and running....

I want to consider installing a second water heater....not sure if to zone it, or in-line with the first one....right now its just a 50 gallon tank.....

my last tank lasted 16 years.....

one top load machine can drain a big amount of hot water.....but I never understand why FL users now go to all COLD washes...whats the most its gonna draw, 3 or 4 gallons....that's the reason I use hot or warm washes, even running several machines is no big deal of energy usage....

beekeyknee · Jul 7, 2014

I just measured mine and it reads 130 degrees. I just got a KDS-60 (KDS-20) about a month ago and I'm noticing some things not coming clean, like smoothies that have been left to dry on. My mother never has this problem, but her w/h is at the other end of the house, so by the time the machine is done filling the hottest water is just getting to the machine. I've been noticing that this machine runs through it's cycles faster than hers. Could it be that hers is running longer to heat up the water since the heater is so far away. Could that be my problem? She's never had a problem with dishes not coming clean. And we have a water softener. I don't get it. I can tell the machine is running properly by the sound. I've heard it run 3/4 of my life. And this one's had a pump rebuild just recently.

rp2813 · Jul 7, 2014

If that KDS60 doesn't have a water heating option, then you probably need a minimum temp of 140 for it. As soon as the water for the first fill hits cold porcelain, it cools down, then relatively cold dishes, etc. serve to cool it even further, so you're not getting a very hot pre-wash. On lighter cycles, the first fill might involve detergent, which means you'll have a tepid wash temp.

beekeyknee · Jul 7, 2014

Well, I was reading the service manual for the machine and it said that wash times are longer for cooler water and wash times can vary from unit to unit. Since my w/h is so close to my kitchen, maybe I shouldn't flush the water from the faucet to bring hot water to the machine. It might run longer then and work better. At my Mom's we run the water, but as I said, the w/h is at the other end of the house. Could this be right?

beekeyknee · Jul 7, 2014

Ralph,

It says the machine heats the first fill to 150 degrees with 1400 watts and succeeding pre-washe and main washes are heated with 700 watts while the pump is running. That's the dual Calrod working, I suppose. I'm guessing that the water entering is to hot and causing the machine to run short washes? Maybe I should turn down the w/h? It does pause and heat the first fill to condition the tank and dishes, but it sure doesn't take very long. My Mom's heats much longer. Could this be the problem? Where's stevet when you need him? I need your expert advise. Or someone else? John, maybe, if you're home yet.

B.

rp2813 · Jul 7, 2014

Brian, I think you may be on the right track, but KA experts will know better than I would.

You may want to start a separate thread on this that will get the attention of Steve T.

gusherb · Jul 7, 2014

We have a 24 year old Ruud gas water heater with a thermostat that is not so accurate anymore, I try to keep the temp around 130, this past winter I got it to about 150 because it runs out too fast otherwise, due to our incoming water being 40 degrees and I like long hot showers.
I plan to get it replaced with a 75 gallon Rheem by the end of this year, next year new DOE regulations will basically force standing pilot natural draft WH's out of existence (I love the reliability and fact that they work without power)

revvinkevin · Jul 8, 2014

Thank you for all the info everyone! I turned it down a little today and will check the temp again in a couple days.

Kevin

chachp · Jul 8, 2014

Wash times KDS 20

Brian,

My daily driver is a KDS20 and it does not circulate water while heating. It just sits and heats the water. The variable times in the two machines you mentioned is likely due to the water temperature entering the machine but I didn't think the water temps adjust the actual time the machine circulates water so once the water hits the right temp I would think that evens the playing field between the two machines.

If you are only having performance issues on the top rack only have you looked at the underside of the rubber tube that carries water to the upper wash arm? I had a similar issue in mine and it turns out the underside of mine had a huge gash in it and the upper wash arm wasn't getting the water pressure it should. As soon as I replaced that tube my top rack cleaning issue went away.

I'm referring to #14 on the attached. From what I understand it is common for these to fail and I have seen this part still available on places like Repairclinic.com. In my case I had an extra rack with a good one so I just swapped them.

magic_clean · Jul 8, 2014

Just an

observation Brian..........in picture # 6, it appears the lower wash arm is not fully seated on the shaft of the wash arm support. The stainless steel shaft should be flush with the top of the bronze wash arm bearing. This will negatively impact washability.

...L.P.

combo52 · Jul 8, 2014

Ideal Water Temperature

120F should be fine if your DW properly boosts at least the main wash and the final rinse, I would never go past 130F for the sake of the WHs life and the life of all the hot water plumbing inlet valves hoses etc in your home [ to say nothing about a huge waste of gas or electricity of heating water any hotter than that ].

KA KDS-20 DWs do not do a good job of heating water, the only way you get any real heating is to run the Soak N Scrub cycle + the sani-rinse option, so you really have to keep your incoming water temperature near 140F. I have the KDSS-20 and keep my WH at 130F and the KD does ok but no where as good as my 1987 WP when I use the Hi-Temp Wash option.

The problem with Hobart designed and built KA DWs is none of them ever had a thermal hold in either the main wash or final rinse so not only do you have to keep the incoming water temperature pretty high and even so the wash cycles were often too short to clean really dried on food soil off dishes.

John L.

jeffg · Jul 8, 2014

John, the problem is that a certain amount of heat loss occurs between the tank and whatever appliance it's servicing. At least from years of advice from Launderess and others here, the traditional wisdom is that 140F is required to kill most nasties, anything less and some kind of bleaching agent (chlorine, oxygen etc) is required to do the job. But to actually get a washer full of 140F water, especially in front-loading machines where very little water is used in the first place, normally requires at least 150-160F water in the tank.

If any or all of the above is incorrect, I'm open minded and would appreciate an explanation of why it's wrong.

washer111 · Jul 8, 2014

@jeffg

Your comments were supported by G.E. in the 80's with their literature for dishwashers.

I don't have any material I can post right now, but if you searched manuals for the GSD1200 or 2800 series, you'd find they suggest something along these lines (This is not word-for-word):

Start the machine on a normal cycle. Allow the machine to complete one rinse phase, and refill for a second time. Then, stop the machine and place a candy or meat thermometer towards the centre of the tub. If the water is not 120ºF, then you must set your water heater hotter.

Later on, they simply suggested running the tap hot, filling a glass, and taking a measurement. The former was more accurate - since you actually had some approximation of water was REALLY entering the machine.*

*If the machine was taking several fills to get "Strong-Hot" water on-tap, then setting the heater higher may not deliver hot water faster, but means when it eventually gets there, it can cause a larger temperature rise than the cooler water might.

I.e. Just because the water is 120º when it enters the dishwasher does not mean the tub temperature will be 120º. It will take several fills for this temperature to be reached. I have witnessed this with the DishDrawer: First fill with 120º water, gets me to about 86-90º, depending on room temperature. Second fill is about 95º. Based on that alone, it would take 3-4 fills to get anywhere near 120º.

During the rinses, it stays at about 120º, and maybe drops a little, depending on the cycle and length of each rinse (Typically 3-10 minutes). {These readings were taken with the machine's on-board diagnostic sensor. It can display the temperature, in ºC when the machine is operating. Therefore, I expect the readings are reasonably accurate}

jeffg · Jul 8, 2014

As far as we've ever read, 140F is and has always been considered the minimum temp for sanitary washing in industry/commercial standards, in absence of bleach. Again if this is bad info I'm hoping someone will correct it.

Water heater temp's, what's the ideal Min – Max?

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