Heat encroaching on the cold water inlet


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Old 01-11-10, 05:26 AM
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Heat encroaching on the cold water inlet

The cold water supply line into the hot water tank get very warm. The fridge line is just above the tank so that water also runs warm. The next closest faucet (kitchen sink) starts warm but cools down after running a few moments. Similar behavior the farther away the faucet is from the water heater.

I think heat from the water heater is migrating up the cold water line. Space is limited in the H20 closet - is a heat trap or expansion tank best? Should it be both or ???

There's no check valve, expansion tank or heat trap installed today. Plumber says "dont use check valve but expansion tank and heat trap (putting a U-bend on the inlet pipe) will help."

Its a 60 gal. electric which geothermal heat pump assist (pre-heats water and circulates it into the bottom of the tank).
 
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Old 01-11-10, 03:37 PM
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I've moved your questions over to the 'water heater' forum.

Not sure why your plumber is saying not to use the check valve, because that probably will help. IF you go with a check valve, you absolutely MUST install the expansion tank.

A heat trap doesn't necessarily need to be a 'U bend' on a domestic water system... you can just use elbows to drop a foot or so below the top of the tank, then elbow back up again. You should probably have a trap on the hot outlet also, perhaps more so.

Check your 'dip tube' in the tank, if the dip tube is intact it should allow very little 'migration' of the hot water up the cold pipe.

Are you on a private well? What you describe is more likely to occur when there are pressure swings such as would occur on a private well system. If this is the case, a heat trap may not be all that effective. Check valve is the way to go for this case.
 
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Old 01-12-10, 05:11 AM
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Heat encroaching on the cold water inlet Reply to Thread

Plumber said not to install check valve because of the "constant" circulation to the heat-pump pre-heater (de-super heater). I dont know anything Your thoughts on the dip tube could be because the DSH injects hot water into the bottom of the tank. Good point but there is no way to get the dip tube outlet below the DSH input - DSH is tied into the bottom of the tank at the drain valve.

Not a private well. Again, could be the circulation by the DSH pump that causes pressure variations.

Thanks for the thoughts. If anyone reading the "Water Heater" forum also has some input I would appreciate!
 
 

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