What Is The Right Temperature Setting For A Water Heater

Tom_22

I understand something like 120 F is scalding. So is there any reason to set a residential hot water heater higher than that?

TomBk

EJW

Water Temp.

120 is what you want but you might need hotter water at certain places like the dishwasher. If you use a tempering valve on the water heater you can increase the temp. of the water heater and connect the dishwasher before it. Then you can set the tempering valve at 120 for the rest of the house. EJW

Mark Hunt

Legionella


is a nasty germ that can grow in a water heater under 140 degrees.

We install ours with tempering valves and run them at 140+.



Mark H

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Firedragon_4

A perfect situation would be 140 F to kill

off the bacteria leaving the heater and no more than 111 F to prevent scalding at the tap according to the AMA. Only one device that will do that, an anti-scald valve.

Mike T., Swampeast MO

All kinds of reasons that people set a temp higher than 120°.

Some like really hot showers. I get bitter complaints in the winter when the thermostatic shower valves "run out" at around 120°. I've measured temp of some people's hot showers—-133°-137°.

Higher temp at the hot water heater will frequently give you "more" hot water as for many uses it will be mixed down in temp. A DHW system that would be undersized at 120° is often quite adequate at 140°.

Some buggie boos can still survive at 120°.

With dish washing, some clothes washing and really heavy cleaning, temps above 120° are often needed.

REASONS NOT TO SET ABOVE 120°.

Prohibited by most codes unless a tempering valve is installed at the hot water source.

Definite scald hazard--particularly to infants and elderly.

Generally wastes energy.

Jack_21

Temp

If you bathe in water over 105 you are no longer bathing but par-boiling. Thermostatic shower valves are set for 112, if I'm not mistaken. I have a Rinnai Continuum (I represent the company) on demand water heater and I have a temp adjusting touch pad in each of the bathrooms (96-120) and a higher temp (96-140) controller in the laundry room. When drawing a bath I set it for 104 and the unit makes 104...all day long. If I want higher temps I can set them. We each seem to have a preferred use temp. I never need over 120. You set higher temps in a tank because they do not have the reocvery rate. You have to run higher temp water to mix it down to get the capacity. Legionella is handled by simply setting the unit to 140 and running each faucet at that temp for about 10 min. Then go back to safe operating temps. No tempering valves required. No superheated water required. At a 70F temp rise the unit will make 4.5 GPM all day long, night too. BTW, the vast majority of these being sold today are using only one touch pad typically set at 120. This is primarily due to them being wired controllers. This fall the controllers will go to wireless and then they will be much simpler to install.

Tom_22

Can The Buggy Boos Live In The Pipes?

Hi Mike and All,

It sounds like if going with a conventional hot water tank heater it's best to set it at 140 F. If a tempering valve is used, can the buggy boos live in the downstream piping and faucets etc.?

TomBk