I have a check valve for my sump pump output that chatters quite a lot at the end of each cycle when the pump runs.

This is definitely coming from the check valve. It's a pretty standard rubber flap type. It would seem to be some kind of vapor lock/vaccuum/suction type problem, but I don't know for sure how to approach it.

I noticed the bouncing chatter happening during the first wet weather after we moved into this house, but I didn't think too much of it once I figured out what it was. Over a year or two it eventually stopped. Come to find out, the body of the check valve developed a crack above the level of the flap. That allowed a trickle of water to leak back down the pipe and back into the sump, but apparently also "solved" the chattering problem. I replaced the check valve with a good one of similar design. No more leak, but the chattering is back... and seems worse than before.

Any tips?

Would this be a swing or spring check valve? Tom

Would this be a swing or spring check valve? Tom

I'm pretty sure it's a swing type. The old one (which at one time exhibited the same problem) had a transparent body and you can see the flap hinged on one side. The new one is black plastic and I didn't give much thought to the idea that there might be a difference when installing it.

On the shelf at Menards there was only one type of "Sump Pump Check Valve" in two sizes (1 1/4 and 1 1/2)

I should have asked, Is it mounted horizontally or vertically? Tom

I should have asked, Is it mounted horizontally or vertically? Tom

It's mounted vertically, about 3' of pipe above the pump. From there it goes to the top of the basement wall (9'), makes a bend to run about 3' horizontally, then another bend to go outside the house where it goes into a drain tile in the yard.

To flesh out my previous answer, it occurred to me that I really shouldn't make too many assumptions. I assume there is no spring in this check valve, but it's just an assumption. The old one definitely had no spring... just a rubber flap hinged on one side. I assumed the new one was the same, but I can't tell from looking while it's installed. (But the body is the same general size and shape.)

Thanks for your help.

Swing check valves work best when mounted horizontally. I suggest that you install a spring check valve if it will be mounted vertically. Regards, Tom

Swing check valves work best when mounted horizontally. I suggest that you install a spring check valve if it will be mounted vertically. regards, Tom


I'll give that a shot and let you know how it works out. Thanks for your help.

Hey, just to let you know, the spring type valve was the perfect fix. Thanks.

The local hardware only had the brass body kind for ~$25 and I would have had to work out threaded fittings to transition from the brass threads to the PVC pipe, but then I found a PVC version for about $7 at a big-box store and it works great.

Thanks again,

Bill