Hot water from cold tap

[sailorchic34]

Originally Posted by CaptTom

Wouldn't the check valve be on the cold (inlet) side? I'm thinking the rest of the hot water plumbing would be able to absorb the expansion from the heating cycle, but just a wild guess.

Yes the check valve would be on the cold water inlet to the water heater. Water is not compressible under normal pressures and your looking at roughly 8 oz of expanded volume for a typical 6 gallon water heater.

[lateral]

We have cold water expansion valves on the bottom of our domestic cylinders on inlet & I have never seen one emit anything. "Yea old rules" had none for a closed system.
They just want stick all these "value enhancers" all over the place so they can charge more. Half the time my clients want em off. On for the inspector off for decent hot water. My plumber sayes "yeah whatever take it off yourself."
F$#king liability. (But we don't have ice.)

[sailorchic34]

Originally Posted by lateral

We have cold water expansion valves on the bottom of our domestic cylinders on inlet & I have never seen one emit anything. "Yea old rules" had none for a closed system.
They just want stick all these "value enhancers" all over the place so they can charge more. Half the time my clients want em off. On for the inspector off for decent hot water. My plumber sayes "yeah whatever take it off yourself."
F$#king liability. (But we don't have ice.)

I must not understand NZ English all that well. Pardon but I assume a expansion valve is a pressure relief valve. If you have a accumulator/expansion tank installed after the pump, the heated water backs up into the accumulator and the relief (expansion?) valve does not pop. Add a check valve on the inlet and it, that is the relief/expansion valve will pop.

I for one don't think a check valve is worth all that much, Though some manufacturers, mostly british, may require one due to the material of the tank.

[hycslim]

Found the problem. As suggested it was the check valve on the cold water feed to the tank. Took it off today, there is a flapper valve inside that was stuck open. Cleaned it up and reinstalled it and the water system works fine.

Thanks for the help.

Allan