Water Hammer

[Greg]

I have a submerged well pump and well troll pressure holding tank.  I also have a sediment filter that is just downstream of the blue pressure tank.  I have a problem with water hammer when the well pump kicks on.  Sounds like someone in the basement is hitting the wall with a sledgehammer.  The problem seems to occur after I clean the sediment filter.  I have to close two plastic screw type shut off valves to allow me to open the sediment filter to clean the cartridge.  I also open another valve which bypasses the sediment filter.  The cheap valves don't fully close so I  put a bucket under the sediment filter to catch water that trickles  out of the sediment filter housing.  I always seem to get air in my pipes from this periodic filter cleaning.  I think this is the source of my water hammer.  Yesterday I turned my well pump off and took the water pressure to zero.  I opened the drain on the blue tank to fully empty it.  I then turned the switch on for the submerged well pump and now it seems like the water hammer is resolving.  I checked the pressure on my blue tank and it was 28.  My tank is set 30 to 56 psi.  I've read your posts on check valves.  I have one that is built into the manifold just as the water line exits the blue tank.  Also one submerged I assume.  Would replacing my cheap plastic screw valves with better ball valves fix the problem and avoid air in the system when cleaning the sediment filter?  Should I remove the check valve connected near my pressure switch on the blue tank?  Thanks

[Cary Austin]

That problem is nearly always caused by the aboove ground check valve.  But this check valve should be on the "inlet" side of the pressure tank for any of this to make sense.  If so, then yes you need to remove the above ground check valve.  However, this check valve is probably masking the real problem, which is that your down hole check valve is leaking back.  The down hole check may not leak back after you remove the above ground check which puts full pressure on the bottom check, and may make it seal better.  If after removing the above ground check valve the pressure leaks off when you are not using any water, the bottom check will have to be replaced.  But you won't know until you remove the above ground check and see what the pressure does.