water hammer

[mblair441]

I have equipped a new well with an AY McDonald 1hp 20gpm submersible set at 90 feet. The 50/20 pressure switch is set downstream from the CSV.  I have set the CSV140 both upstream and downstream from a surface checkvalve. Either way  I get severe water hammer when I  open up at full flow. Does the pump have an internal check? Do I need to remove the upper check?

[Cary Austin]

The extra check valves will cause water hammer at pump start or pump stop.  You must have a check valve on the pump itself, and that is the only check valve you need.  But if the water hammer is happening when you "open up to full flow" then you probably have too much air in the pressure tank.  You need to change the pressure switch setting to 30/50, and make sure you have no more than 25 PSI air charge in the tank.

[mblair441]

the tank is one of those little 2 gallon surge tanks. It is set about 6 inches downstream from the pressure switch and about 12" downstream from the csv. The pressure switch is a new Square D Pumptrol, factory set at 30 on 50 off. Does my pump have an internal check? Is the set up correct if I remove the surface check valve that is between the pump and the CSV?

[Cary Austin]

All submersibles should have a check valve either built in or attached directly to the pump.  This is the only check valve needed.  You can remove any above ground check valves, which will stop water hammer on pump start.  If the check valve on the submersible is bad, when the pump shuts off, it will come right back on even though no one is using water.  If that happens the check valve in the well will need to be fixed or replaced.

[mblair441]

I removed the surface check valve. Turned on pump and it ran smoothly for 10 minutes until I closed the faucet. The pump cycled off and then it cycled on and instantly off about every 15 seconds. When I turned the water on again, it started hammering. The pressure switch is between the CSV and expansion tank.  All this equipment is new so unless the sub. pump is defective or the CSV is defective, I'm not sure what else I can do

[Cary Austin]

If the pump comes back on when no water faucets are open, water is going somewhere.  It is probably going down the well to a bad check at the pump or a hole in the drop pipe.  See if water is going back down the pipe in the well.  If it is, that has to be fixed before your problem will go away.

[mblair441]

I pulled the pump string by hand  . If we are decended from monkeys, why didn't we keep the prehensile tail. I sure needed an extra hand.  It appears that a joint was cracked at one of the collars, because it broke as the pipe flexed. I guess that was where I was losing pressure and water.  Below that connection, the pipe stayed full of water so I knew that my pump check was good. I put a second check two inches above the pump and replaced all the couplings and fittings with stainless steel. Man, those babies were expensive.  .  I ran it back down the hole and it appears the problem is fixed. Thanks for the help!

[Cary Austin]

I am glad you got it working.  After talking to you and finding out you had threaded PVC couplings, I was afraid that would be the problem.  Metal couplings are much better than plastic ones when using threaded sch 80 PVC pipe.