Tank cold water inlet is hot... recirc issue?

6 years ago

We think we have a faulty sink or shower valve as we have a lot of hot water somehow getting into our cold water. We also have insufficient hot water where we need it.

We also have a hot water recirc system.

In sorting out the mess, I noticed that the pipe delivering cold water to our electric tank water heater (about 2 feet of exposed pipe) is very warm, almost hot.

Is it normal for the cold inlet to be that warm? We are on a private well that delivers very cold water.

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Comments (5)

Jake The Wonderdog
6 years ago
a recirculating system will eventually send the water back to the water heater on the cold side.

I would try temporarily turning off the circ pump and shutting off the valve to the circulating loop to take that out of the equation.
piegirltoo thanked Jake The Wonderdog
klem1
6 years ago
Do you realize snuff drooling plumbers often go out on jobs like this and don't find the answer after 3 hours and $500? I seriously doubt anyone can answer your questions free without seeing the place.
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I agree with nigelsgarden that the recirc should work. Did you run a new line back to the hot water heater and feed the recirculated water back into the cold water inlet fitting on the heater? There are easy to install recirc pumps which use the cold water feed to the bath room as the return pipe. The problem here is that with the recirc pump running you won't have any cold water, because the cold water pipe will get packed full of hot water. Mark, if you saw anything discouraging feeding the mini hot tank with the hot water line it would have been to avoid the following situation": 1-You start showering, and the tank gives you nice hot water right away. 2-The nice hot water you use from the tank is replaced by the cold water in the 50 feet of pipe from the hot water heater to the bathroom. 3-As the limited supply of hot water in the mini hot tank starts to become exhausted, the shower will begin to cool down, because the cold purge water is filling the mini hot tank. 4-The shower probably won't go completely cold, because when the pipe purge is done, there will be hot water from the big hot water heater filling the mini hot tank, and the outlet temperature will rise again, until the temp at the shower equals the output form the main hot water heater. If you like to sing in the shower, the cold phase might give your voice a nice operatic vibrato (caused by shivvering) and the arrival of the very hot water can help you with a couple of high notes till you get everything regulated.
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Scott, FWIW, whether you have an expansion tank or well tank (which you have) doesn't matter a bit as your problem has nothing to do with a pressure/expansion tank. Woodbutcher (above) describes the application of both tanks correctly, they are identical inside and only differ in size. The issue appears to be a cross-connection between the hot and cold water. Your statement "I turned off the cold water intake to the water heater and the water started running straight cold" confirms this. - Dou you have a hot water tempering valve (usually close to the water heater) that could be back feeding between the H/C? - You said you already looked for a hot water recirc system and didn't find any. - Are there zonal shutoff valves (usually not!) so that you could isolate the problem to certain areas of the house? - If you shut off supply lines under sinks does the problem stop? - Diagnosing showers and tubs can be a problem because they can be piped as a bathroom group (lavatory + toilet + shower/tub) or individually off the supplies. If the shower/tub controls have built-n stops (uncommon) you can shut them off individually behind the faceplate. - Maybe shutoff EVERY faucet and shutoff valve inside/outside the entire house. Then start opening them one at a time, maybe repeat in different sequences. Hopefully you can physically isolate where the problem is in the house.
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piegirltoo
Original Author
6 years ago
Thanks, Jake the Wonder Dog, I'll try that.

klem1, I thought my question was pretty straightforward: "Is it normal for the cold inlet to be that warm". I wasn't asking for an overall diagnosis. I realize I may have a complicated plumbing problem. I'm not even sure why you bothered to respond.
Jake The Wonderdog
6 years ago
piegirltoo: So often a recirc system includes a temp sensor on the return loop that shuts off the pump when the return loop near the water heater gets warm (indicating that the hot water is completely circulated).

It's not uncommon for the return (cold water inlet on water heater) to be warm, but may indicate that the pump is running too much if it's hot.

Do try to limit the possible causes by temporarily shutting off the circ pump and closing off the valve to it (don't forget to open the valve before you turn the pump back on).

If you still have the issue with the circ system shut down, your next place to look is mixing valves. I've seen backflow through laundry sinks (they left hot and cold open and had a hose shutoff on the spout). I've seen backflow on anti-scald tub and shower valves also.

You can isolate a mixing valve by closing off either the hot or cold water to that valve and see if you still have the problem.
piegirltoo thanked Jake The Wonderdog
piegirltoo
Original Author
6 years ago
Brilliant! Thanks again. It's an interesting puzzle. We did have a plumber (a friend of ours) here for another purpose. He worked on sorting it out, but had to move on to another job. I'm sure he can fix whatever needs to be fixed, but he's out of commission for a few months with an injury (not work-related!) . Meanwhile we're taking cool-ish showers, which is ok just for summer.

Tank cold water inlet is hot... recirc issue?

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Tank cold water inlet is hot... recirc issue?

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Jake The Wonderdog

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