Sump Pump Knocking

 
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Old 04-27-2011, 10:39 PM   #1
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Sump Pump Knocking


Hey there.

Just installed a sump pump... well my plumber did actually. HO told me over the weekend that it was knocking. They have a bedroom right above.

Plumber explained to me that it was the pump stopping. It just shuts off, causes a wave in the outgoing water line, back and forth, etc..

But this was some crazy banging. I even held the pipe tight, to simulate a good fastening job and the thing was loud. Is this normal? The plumber's boss thought it might have been a failing check valve (he didnt see it)... The runout is about 25' 1-1/4" abs.

Are there solutions? Does a hammer arrest work in this situation?

Regards, Mike.
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Old 04-27-2011, 10:48 PM   #2
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Re: Sump Pump Knocking


Well, one thing that makes a big difference is the type of pump and the type of float. A pump that has a high GPM rate combined with the right float can really make noise.

If possible go buy some armaflex and a 3" J-Hook to support it. It will act as an anti vibration support. Just a small piece wrapped around where the J-Hook goes can really make a difference.

Mike

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Old 04-28-2011, 10:41 AM   #3
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Re: Sump Pump Knocking


I have a Flotech pump in the laundry tray under the slop sink in my basement that has a inline check valve at the base of the pump and it will make a noticeable clunk when it closes after pump out, but I only hear it when I’m in the area of the slop sink and wouldn’t really consider it to be abnormally loud.

Maybe the sound from the check valve is telephoning up the pipe in your situation. Did the plumber install a banded no-hub coupling on the drain line at the pump? If so, I’m wondering if maybe installing another regular rubber Fernco coupling on the drain line, in the non-pressurized part further downstream, might help isolate the noise.

Last edited by DuMass; 04-28-2011 at 10:43 AM.
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Old 04-28-2011, 11:59 AM   #4
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Re: Sump Pump Knocking


Change the piping so that the check is on a 45 degree angle, it will reduce the closing noise.
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Old 04-28-2011, 08:32 PM   #5
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Re: Sump Pump Knocking


SB,
I think it also may depend on the type of check valve, but all of them I have installed (100's) have mad that banging sound. How high is the vertical head on the pipe? Seems to me the loudest ones are always the ones with the most vertical rise before going horizontal. Just food for thought.
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Old 04-28-2011, 09:10 PM   #6
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Re: Sump Pump Knocking


This noise is a little unusual - It's about 15 bangs, it takes about 10 seconds to stop banging. I think it is anyway.

It goes up 8 foot, then horizontal 25 foot. I'll see if I can get him to get the check valve on a 45, and put another fernco in there.

I'll just have to figure out how to provide this advice: "I was online and this plumber said I should..."
... nah, I'll go with one that always works:
"I was watching this episode of Holmes on Homes and..."

Thanks folks!

Mike
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Last edited by sbcontracting; 04-28-2011 at 09:16 PM.
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Old 04-28-2011, 10:36 PM   #7
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Re: Sump Pump Knocking


Hey, before you get to cared away here you better make sure the outlet isn't plugged or partially blocked. If it's that bad it sounds like pressure is building because of resistance.

One more thing to check is the float. Look and see if it hung up. Sometimes pulsating in the pipe can be caused from a bad float or a float that takes it's time shutting off.

Sounds like an interesting problem, let us know what you find.

Mike
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Old 05-07-2011, 07:14 AM   #8
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Re: Sump Pump Knocking


put in a "quietcheck"
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Old 05-08-2011, 08:48 PM   #9
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Re: Sump Pump Knocking


They changed the check valve, has a hammer arrest built into it. Seems to have done the trick.

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