my water hammer problem better explained

[Bennet Young]

I am very new to all of this but let me try to further explain my situation. The pump was taken out from under the house and put in the garage for ease, There was no leak we just added on to the poly with pvc to get from under the house to the garage. The pump is a shallow well 3/4 hp Goulds. Right before the pump the pvc goes into a brass check valve and then a pipe goes from there to the pump. The lound thud happens when the pump shuts off. Are you saying that this could be an inadequate or faulty check valve? Also, please explain to me the differance between a check and foot valve. Thanks for your help...

[Bob NH]

A foot valve is a check valve at the bottom (foot) of the pipe in the well. It is usually combined with a strainer.

When the pump is pumping the water is moving. When the pump shuts off the water wants to keep moving (inertia), but the pressure makes it stop and start to reverse flow. As it reverses, it closes the check valve. The longer it takes to close, the faster the water is moving backwards and the louder the noise.

The greater length of pipe that you installed when you moved the pump to the garage has more water with inertia and energy to make a noise when the valve closes. I suspect that you moved the pump but not the tank. If there is a long enough column of water moving fast enough, and the pressure is low enough, it is possible to create a vacuum bubble in the pipe. That will cause more noise when it collapses.

Many check valves are spring loaded so they close quicker, and therefore with less backward water velocity and consequently less noise.

You don't need a check valve at the pump if you have a functioning foot valve. Also, if the foot valve is noisy you aren't going to hear it.

[Bennet Young]

Thanks for your response. I moved the tank as well. I put about another 25 feet of pipe on to relocate it. Can you tell me what I can do to stop this hammer at the pump. It didn't do it before and its very annoying. But the worse thing is that my wife is mad at me!!!! Would a different check valve fix it? Please help...

[plumber1]

If you need the check valve, you may need to use a soft seating, spring loaded check valve.