Dripping overflow from pressurised CH system on duplex tank line

[Andrall]

There is a constant drip from the 22dia overflow line which terminates at the HW cylinder but it is not the cylinder which is leaking as the tundish is always dry. There is cold water feed to the cylinder which has branches to 2 off expansion vessels with a PRV which can release across into the overflow line. I have set the expansion tank pressure which has a 15dia overflow to 1.5bar but this can decay by up to 1bar in 24 hours. I have attached a schematic which might assist.

Additionally, there is the PRV immediately downstream of the pump prior to the zone valve that externally leaks intermittently through the top of the body but not enough to be real problem as I have a tray under it to catch the water. I do not know the purpose of this PRV but it has a black plastic truncated cone shaped cover which when turned alters the spring pressure in vertical 0.1bar increments and is graduated 0 - 0.5bar.

Thanks in anticipation,
Andrall

 

[Chuck]

Your diagram is displaying to me as a solid black rectangle and I can't make sense of your question without it. A couple of pictures showing the problem areas would help too.

 

[Brambles]

If you have PRV’s that are operating / leaking or passing you need a decent plumber in to investigate and resolve. Sealed systems should not have perceptible leaks

 

[Andrall]

Gents,
Thanks for your input. Original black image was in error. Correct schematic now attached together with a photo of externally leaky PRV.

Regards,
Andrall

 

[ShaunCorbs]

If it’s the one with the numbers up the side that’s the auto bypass valve, when the port valves shut it allows the pump to still pump round via the bypass