I just installed a new valve (Hunter HPV). Everything works well except when the value is opened there is a fairly violent sounding thump-thump-thump sound. After 3 quick thumps, everything works well. When the valve shuts off, everything is very smooth. I have about 78 PSI coming into the valve. This happens on a recurring basis. Reducing the flow control significantly makes this go away.
I am trying to understand this problem better. Wet Boots provided the following comment in another thread about banging when the zone is first opened (as opposed to closing).
Also, note that there is banging when the zone is first opened, and that is not water hammer. It is something of an oscillation you can sometimes see when a system is first opened in the spring, where there is no water in the zone for the supply to 'push' against. When it happens on a recurring basis, you look to make changes. Installing check valves in the heads is one obvious choice nowadays, to keep a zone full of water, so there's something to 'push' against. Throttling down a zone valve flow control is another option. Changing zone valves is another.
So according to this, I have 3 options. 1) check-valves in the heads. I can try this, but I don't think anything is draining since the zone is very flat and nothing is noticeably draining. Should I still try this? 2) flow control - this works, but only if I reduce the flow significantly. 3) changing zone valves - what kind of zone valve would I try? What would it do (ie: feature) that the Hunter HPV isn't doing?
Thanks,
-Jeremy