Tempering valve operation

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Mikey

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My hot water tank typically has water at 150 degrees or so, which is fine for the laundry and dishwasher, but a little toasty for the bathrooms. As luck would have it, those two zones are in different directions from the water heater, so I'm thinking of installing a tempering valve to service the bathrooms. The problem is that the cold water stored in the pipes can be up to 120 degrees, since the pipes are in an attic in Florida.

My question is -- what happens with a tempering valve like the Watts 70A or L70A if it is set to, say 110 degrees, if the incoming "hot" is 150, and the incoming "cold" is 120? I'm guessing it will flow 100% "cold" until "cold" goes below 110, and then start adding "hot" to keep the output at 110.
 

hj

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heater

Then you do like a friend of mine used to do. He shut the water heater off so the water inside it would be at the house temperature of 75 or so, and used the 120 degree cold water for his hot and the "hot water" from the heater for his cold. But yes, the tempering valve will try its best to give 110 degree water.
 

Mikey

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Well, some like it hot, they say. My solar system keeps the stored water at over 150 on a good day, and I like it that way. I think I will put in the tempering valve, but the anti-scald shower valves are on their own for a while.

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Jadnashua

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The place I lived in Kuwait had the water tank on the roof getting so hot, the only way to get cool water was from the turned off WH in the house...it was hell if you ran out of that cooled water, since its input was hot and the insulated tank kept it that way for awhile. They only had running water a few hours of the day, you needed the tank (and gravity) to provide water the rest of the time.
 

Mikey

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I wonder if you could put a 2nd tank on the roof and expose it overnight when it can get pretty cold, then cover and insulate it during the day, to accumulate cold (or at least cool) water?
 

Jadnashua

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At night, it might drop to all of 90 or so, so, no, it wouldn't cool off much. Anyways, that was 25-years ago, and I only mention it for interest.
 

Master Plumber Mark

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Installing the tempering valve

You will probably mess up the
anti scald valves in your bath tubs and showers
with the tempering valves



They won't get a good reading if only 120 comes to them
and will probably fluctuate.....



Why go to all the trouble when you already have the
anti scald valves in place??
 

Jadnashua

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The anti-scald valves do two things, adjust the temp due to pressure variations between the hot and cold, and, only if you set it, adjust the maximum amount of hot water you can introduce into the mix. The big deficiency in this is if your incoming cold water varies a lot between winter and summer - you may not get it as hot as you like if it was adjusted in the summer, or if adjusted in the winter, it may end up hotter than you prefer. But, it works (within its limitiations) regardless of the incoming water temperature.

A thermostatically controlled valve basically doesn't care about the temperature of the hot water, as you have a tempering valve in the thing directly. It only becomes a problem if the cold water is hotter than the setting...it can only limit the hot, and give you (mostly) water from the cold side. If that is hotter than the thermostat setting, I don't think (I do not know) if it will then shut off the flow. I'm pretty sure, the limits of its capability is to only automatically adjust the mix, not restrict the flow from both supplies.
 

hj

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valve

A thermostatic valve reduces the cold flow to raise the temperature, and cuts the hot water flow to reduce the temperature. If the cold water temperature is higher than its setting, then it will completely stop the hot water flow and allow only "cold" water to flow.
 
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