hot water from cold water line

mikea23

First your water service pressure is way to high install a regulator and drop to 70psi. that can solve the problem if not check shower bodies

dave price

hot water in cold water line

Recently, I have noticed that after sitting idle (like over night for example)a short duration of "hot" water is discharge from the cold water side of the sinks in my home. The nine year old, gas fired, 75 gal, Rheem water heater (model 21VR75 ) does not seem to operate excessively longer than usual. Following demand for hot water, it appears to cycle normally and shuts down as it should. The only recent change to the system was, setting the water heater to "vacation" while we were out of town last week and returning it to the previous setting upon our return.
As for the system itself. All the pipes are insulated and there are not any double check valves in use. Finally, the static municipal water service pressure runs between 80 psi (summer) and 120 psi (winter).
Any ideas why this is happening are more than welcome. Please advise!

Dave

J.C.A._3

Or washing machine valves for hot water crossing to the cold side.

I agree, the pressure is too high.

Larry C_13

House check valve?

I'll bet the water main has a check valve or a non relieving pressure regulator.

I assume it occurs only after a large hot water load has happened. The water heater is full of cold water. As it heats up, the warm water expands. The only place for the water to go, is back out the cold water inlet. It then rises in the cold water lines to the sinks.

How did you determine the water main static pressures? Did you use a peak recording pressure gauge?

I would suggest having a plumber install a thermal trap to minimize the amount of hot water migrating into the cold water lines. Or, another possibility is to install an expansion tank in between the water heater inlet and a check valve.

Check with a licensed plumber as to the legallity of the second suggestion.

Larry C

dave price

Static pressure is determined by by a Weksler EA 14F Pressure Gauge with a 1/4" NPT bottom connection, permanantly fitted 3ft aft of the load side of the meter. The siamese washing machine valve is regularly closed when not in use, there has not been any mechanical changes to the entire house at all. And as for the water main, there is only the conventional (non-remote read)water authority meter inside the house, nothing outside. I am not sure what Mike is refering to regarding checking the shower bodies? Larry is correct about the water in the inlet side of the water heater. That supply line is hot to the touch. But, this situation seems to occur more so over night or after being out all day. Almost a sort of migration back into the supply side you might say.

dave

Marty_9

go here for more help
http://www.waterheaterrescue.com/index.html