Since installation I have had water hammer when the pump shuts off. The installer "never saw this happen before".

The 3/4 hp 8 gpm pump is 140 feet deep, and the well is about 400 feet (horizontal) from the house. The supply line is 1" Kitek. The supply couples into a brass 90, makes a copper 18" run, then another 90, a 30" run to a 3rd 90, and then to a check valve ahead of the Well-Mate pressure tank. The tank is holding 35 psi. I'm running from 40 to 60 psi to the house.

I believe there is also a check valve one section above the pump. "To keep water from draining back", said the installer.

When the pump shuts off there is extended "banging", but not against anything, just coming from the pipes.
Probably 4 to 5 diminishing bangs/clangs per cycle.

How do I start to troubleshoot this?

Thanks,
Greg

Hi Greg,

Check the bladder tank. Pop the air inlet valve on top of the tank. If water comes out then replace the tank. Let me know, Tom

Speedball1,
'Bladder Tank' or 'Expansion Tank' or 'Pressure Tank'?

What I call a 'pressure' tank is my 60 gallon Well-Mate tank with a bladder that sustains house pressure. It's after the checkvalve and my well control sits on the T to it. It is holding pressure and is not leaking water into the dry side of the tank.

If by 'bladder' tank you mean a smallish tank to offset water expansion - I don't have one on the well system. (Got one for the in-floor heat, but that's elsewhere).

Didn't think I needed one, but if I do I'll get it...

Greg

I hope you have found an answer before now (I see your post was made in 2007). I have a very similar problem, but mine is a shallow well with a jet pump. I checked the pressure tank and it was low on pressure, so I adjusted the pressure per the manufacturers instructions. The pump doesn't run as often now, but it still bangs on shut off. According to some other sites, a bad check valve can cause the problem, so I replaced the check valve at the pump. I didn't see much wrong with the old valve, but now I only get two bangs when the pump shuts off. I also read that more than one check valve is a problem. According to your description, you have two. If you still are having problems, maybe you should try removing one of the check valves.

If I have more than one, I don't know where the second one would be.

The issue of CV's causing a knocking sound is usually more associated with submersible pumps rather than jetpumps. At any rate, you might want to use a spring type CV rather than a gate type CV. I would think there would be less "slap". This is what I am referring to: SLSC100T - Hydrovalve SLSC100T - 1" Threaded Spring Loaded Check Valve

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If I have more than one,check valve I don't know where the second one would be.

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You might have az check valve at the pump and a foot valve at the well point, Cheers, Tom

The check valve at the pump is a spring type. I ordered a new one and replaced it under the assumption that the spring had rusted away. But when I inspected the valve, about the only thing wrong with it was the seal had hardened a bit and was actually sticking shut. (Probably why sometimes it would bang when the pump started.)

The water hammer effect has been there since I bought the house. The pump is fed by a 1-1/4" plastic line that snakes through the house before it gets to the pump. According to the pump manual, this line should be 2", and no longer than 200'. (I'm pretty sure it is longer than that, but I'll check today.)

So I may just be dealing with a poorly designed system.

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Originally Posted by speedball1

You might have az check valve at the pump and a foot valve at the well point, Cheers, Tom

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The post I found was very adamant that there should only be one check valve. (I didn't see how two could cause a problem myself.) But the pump manual recommends a second check valve at the well if the horizontal pipe is longer than 25'.

The horizontal pipe is probably 200' to 300', which is actually longer than is recommended for the pump.

I guess I'll try digging down around the well head to see if there is a check valve there. (The line just tees off the well and goes into the ground, so I don't think there's a foot valve.)

So there is one pipe only going into the well? If that is the case, then there is a footvalve at the bottom, which would probably be no more than twenty feet or so down. I'd try just taking the CV off the line altogether. As long as the pump holds prime, you might be able to get by without it.

How large is the pump? 2" line is fairly large.

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Originally Posted by jlisenbe

So there is one pipe only going into the well? If that is the case, then there is a footvalve at the bottom, which would probably be no more than twenty feet or so down. I'd try just taking the CV off the line altogether. As long as the pump holds prime, you might be able to get by without it.

How large is the pump? 2" line is fairly large.

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The check valve at the pump is actually part of the inlet fitting. About all I could do is disable it by taking it apart. Where the manual recommends a second check valve, I'm not so sure it's the problem.

The line to the house is threaded into a tee on the well head, so I think the installation is more of a drive-pipe setup. I don't think there's a separate line inside the well casing. The top of the tee is capped with a threaded cap.

The pump is a 3/4 hp pump. (Sears 390.25120) The manual recommends 1-1/4" pipe up to 25', 1-1/2" pipe up to 50', and 2" pipe up to 200'. The pipe I have is pretty close to 300'.

Where it's the suction line, head pressure is pretty important. At least some of the pipe is plastic (Its metal at the well and plastic in the house) so I wonder if the pipe isn't shrinking a bit under the suction and just generating a pressure wave when the pump shuts off.

Part of the year there is enough pressure for the well to flow without pumping, so I think its at a pressure range that's pretty susceptible to pressure waves.

Its made this noise as long as I've lived here (just less than a year), so it doesn't necessarily represent a component failure.

I've toyed with the idea of moving the pump closer to the well, but the first 200' of the line is on an easement on my neighbors property, and I'm not to sure they'd like the idea of me putting a well house on their land.

The 300 foot run of pipe... does it run uphill or downhill from the well?

I still think I would try just taking the CV off and connecting the long run of pipe directly to the pump. Sound like you were able to take off an old CV and replace it with a new one, so there must be a threaded fitting on the pump.