I have a problem that no professional has been able to answer. The water meter will turn intermittently even when main valve is shut off. Water pressure on my fire sprinkler system has shown values as high as 150 psi. My pressure regulator is set at 65 psi. I have noticed that when the meter turns without any water usage, I can hear a knocking in the pipes. I have also noticed that this knocking only happens when the gas water heater is firing to heat the water. Any suggestions as how this can happen? Thanks.
Heat and cold cause air expansion and contraction if your system is wet it may have a relief valve bumping excess pressure down a drain, If it is a dry system I would make sure the flapper at the wet/dry division is not leaking by this can cause all kinds of trouble but these are usually on large systems, smaller home health care systems I have experience with are wet and as the water in the plumbing heats the relief vents Down a drain. This is much better than a over pressure that starts leaking in the living space.