My house has a mains pressure domestic hot water system (no loft cistern). Seems to mostly work well except that there is backflow through the thermo shower mixer (cold water seeps back into hot water pipe when the shower is turned off). Can't understand how this happens as it's an unvented system and pressure ought to be equal on both hot and cold feeds to the shower. Also where does the displaced hot water go to? One thing I have noticed is that the mains pressure reducing valve is fitted on the cold feed to the hot water tank after the point where the mains feeds to the cold taps. Is this correct and could it be the reason for the unequal pressure? Should I just fit a check valve to the hot feed to the shower?
Any advice gratefully received.
Any advice gratefully received.