water hammer on supply side of pressure tank

9 years ago

The well is drilled, approximately 120 feet deep. It was drilled in 2006 when I constructed my home. In the basement of the house, the main water line comes in and connects to Gould V60 pressure tank. The pressure switch is 30/50 and the bladder is pressurized at about 27. There appears to be a check valve in the T package on the supply side of the T. I have not noticed any loss of pressure in the tank.

My well water system works perfectly, EXCEPT when it has been sitting for a period of time (hour or more). On the supply side of the pressure tank, when the well first turns on in the morning (after toilet is flushed, water running, etc.), there is a single pound hammer that can be very loud at times. Once this happens, as long as we use water on the regular basis, we will not hear the noise again. However, if it sits for a while (hour or more), the same bang.

My theory is that the foot/check valve located at the top of the submersible pump (or wherever it is located), has gone bad, allowing the water in the line from the pump to the pressure tank to leak out, replacing it with air, and causing a hammer-type bang when the pump turns back on.

Unless we use water in the house, the pump does not cycle on/off. I assume that is because the check valve on the t-package is preventing any water in the pressure tank from leaking out.

Any thoughts on other things I can check before calling my well guy to pull the pump and replace the foot/check valve?

Thanks for any guidance.

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Comments (6)

bus_driver
9 years ago
In the hypothetical scenario you describe, there is no way for air to get into the pipe. So the cause of the noise is something different.
law2lake
Original Author
9 years ago
bus driver, Thank you for the prompt response. Is it not possible for the check valve (just above the pump?) to have gone bad, allowing water to slowly drain out over time? Assuming that could happen, I assume the water that leaked out would be replaced with air. FYI, I am very green at plumbing. Thanks.
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User
9 years ago
When there is more than one check valve on a system and the upstream check valve fails, when the pump shuts down water leaks out back to ground. If the leak is small, you will only notice the problem when the pump has been shut down long enough to form a vacuum in the line (because there is no way for air to enter the pipe). Then you get water hammer when the pump starts. Pull the pipe and replace the check valve.
law2lake
Original Author
9 years ago
Can someone confirm that the copper colored piece on the supply side of the T (closest to PVC) is a check valve. This is what I am assuming is the check valve that apparently should be removed.

Thank you.
User
9 years ago
The check valve that needs to be replaced is the one at the pump. If this one was bad, you would not have water hammer.
law2lake
Original Author
9 years ago
FYI, based upon information that I received from other forums, I replaced the check valve just before the tank, and the hammer is gone! And it is holding pressure just fine. Apparently, there is no need to have more than one check/foot valve in my system. Sometime less is more. Quiet as a mouse. Thanks for your assistance.