Noisey bypass valve

[ColinJackson]

I have installed a new heating system which generally works fine. I have a differential bypass valve in the system because all my radiators have thermostatic valves on. When the bypass is not bypassing everythings ok and when the the bypass is passing plenty of water it is ok but at the transistion period when it just starts to open it hums as I guess it is opening and closing quickly. I assume that when it opens it causes the pressure from the pump to drop slightly which then makes it close again. Any suggestions as to what might cure the noise. I have considered putting a length of 15mm on the out feed in order to give a little back pressure which will reduce the size of the 'gulps' it takes from the pumped pipe but I don't know if that will work. Has anybody any suggestions.

 

[oilman]

You could use a gate valve in series with the bypass valve, this would be adjustable, so you MIGHT be able to tune the system. Then again, it might be a faulty bypass valve.