Shower with 100% hot water or mix with cold?

[Ameli0rate]

To elaborate - does it make sense to set the water heater to a temperature where I can shower with the handle to full-hot, or should the water heater be set to a higher temp and I mix hot and cold in the shower?

Does energy savings figure in? If I mix my hot water with cold, I use less water heater water, but I have to heat it more to mix it with cold to get it comfortable.

If I turn it down, I use more water out of the water heater, so it drains faster and has to reheat more water..?

Do flow rates matter here?

 

[Marlinman]

If you put your water heater to 140 and mix cold water to reach 120 you will kill the bacteria in you system and increase the availability of hot water. These valves are readily available from many manufactures.

 

[Sponsor]

 

[Ameli0rate]

Interesting. I was thinking more from an efficiency standpoint (which is more efficient - mixing too hot water with cold, or setting the water heater at perfect-for-full-hot showers) but I never knew about the legionellosis risk, many thanks for the heads up.

While I'm curious about the efficiency calculation, it's irrelevant as I'm not willing to risk our health to save a few bucks a year.

I'll measure my temp at the tap tonight (for my curiosity) and then crank the think up to safe levels. Then I'll call my plumbing guy to see about a tempering valve.

 

[Jadnashua]

Stuff tends to grow in warm water...you really want the tank hotter, at least 120 and some will run it higher. COde where I live requires a tempering valve to ensure the outlet doesn't get hotter than 120. Having the tank set hotter will extend your shower time. All new shower valves have a stop to prevent the maximum temperature from becoming too hot - IF you adjust it properly!

Legionnaires disease is one thing you should look up.

It costs the same to heat water per volume. The higher the storage temperature will mean higher standby losses, but if the WH is in heated space, that heat is not wasted...it warms the area that would have had to be heated via the furnace.

 

[Ameli0rate]

I measured under the tap after my shower and the temp was 119f. Then I waited about 15 minutes to let the water heater cook for a bit and measured again, 125f.

It's perfect for showering, but too cold for germ elimination.

I've turned it up a point or two on the dial, so that should cure that. I am planning for a recirculator in the future, so I could have a plumber do that and the tempering valve at the same time. Then when I remodel the bathroom, the 'crossover' valve (whatever the proper term is for the valve that works in conjuction with the recirc pump is called) gets installed.

 

[Marlinman]

Legionnaires disease is killed at 140 degrees