pipes bang when well pump starts.


Old 12-03-14, 05:24 PM
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pipes bang when well pump starts.

I have a 20 yr old 125' deep well with a 7 year old submersible pump and a Wellxtrol tank and control. The check valve recently failed, so I replaced it and that fixed the cycling problem. Now, a few months later, the pipe from the well to the tank bangs loudly when the pump kicks on. Any ideas?
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Old 12-03-14, 07:27 PM
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Hi Everett Ė

Iím just a newbie to well systems but Iíve done a lot of stuff to my system (except pulling the pump). I think there is a lot of debate out there about check valves and their proper use. I have a submersible pump (75í) and a check valve at the pressure tank in my basement, and my understanding is that there is always a check valve at the pump.

A check valve at the pressure tank will mask a leak anywhere from the pump up to that check valve; so many people say thatís why you shouldnít have a check valve up at the tank. If the check valve at the pump is working properly water shouldnít fall back in the well and the check valve at the pressure tank is not necessary.

Maybe in your case the check valve at your pressure tank was masking a faulty check valve at the pump or masking a leak in the piping somewhere from the pump to the check valve by the pressure tank. So when the check valve by the pressure tank failed you started to see the pump short cycling. Then when you replaced the bad check valve at the pressure tank the real problem was masked again. (But some people say that type of masking is not a problem, you have actually made your system usable. I guess itís all in the eye of the beholder.)

Another thing Iíve heard is that multiple check valves can cause water hammer and thatís why multiples should not be used (some say I guess). Here is one explanation:

Now an extra check valve can cause water hammer on pump start, no matter how the pump is controlled. When not if the bottom check closes just a bit slower than the upper check(s), or leaks even a thimble full of water, the water in the pipe will be held in by a negative pressure. The upper check is working the same as holding your finger on top of a straw full of ice tea. So when the pump is started, the momentum of the water flying up the pipe hits the upper check valve with the force of a Boxer hitting you squarely in the nose. This causes a tremendous water hammer, and in some cases will make the pump and pipe jump up out of the well. I have seen a 100HP pump and 300í of 4Ē steel pipe jump a foot straight up and slam back down when the pump is started.
Sounds good to me, lol!

But I still keep my check valve by my tank and have not experienced water hammer. But I did have a leak in the water service pipe to my house and the check valve by the tank did in fact mask that problem for years.

So maybe if your check valve is bad at the pump and is continually getting worse, that might explain both why you have water hammer and why a bad check valve at the tank caused short cycling.

This looks like a job for PumpMan Ė wherever he may be! lol

Good luck hope the pros jump in!

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