HELP! Due to heavy rain I have some water in the basement which is not unusual since
Flooding after rain happens in this area. However, for the first time (I had a new sump
Pump installed last winter) there is loud banging - s ounds like a vibrating bump, bump bump every time it comes on. Thanks for any ideas about this. :confused:

Grab on the pipe coming out of the pump and see if it is the source of your thump/bang. Your new pump may not be secure and the torque of the electric motor could cause a sharp twist.

Grab on the pipe coming out of the pump and see if it is the source of your thump/bang. Your new pump may not be secure and the torque of the electric motor could cause a sharp twist.

I went to the basement and watched when it was doing the thump, thump sound. After
It has pumped the water out (which goes in a pipe across the top of the basement to the
Outside) and cuts off - then it does the vibrate - thump, thump. I guess it's nothing
Dangerous but it's disconcerting to hear than since it's pumping plenty of water out.

You can safely hold onto any of those drain lines to check for movement. If this turns out to be the case then just clamp those drain lines with plastic pipe hangers or clamps.

The banging sound is created by water column hitting check valve. How high is your (vertica) riser before it turns horizontal ? Do you have plastic or metal drains ?

Check valve should be installed about 12" upward from the pump discharge outlet. In your situation, you will have to install another check valve on vertical pipe, right before it turns from vertical to horizontal.

The banging sound is created by water column hitting check valve. How high is your (vertica) riser before it turns horizontal ? Do you have plastic or metal drains ?

Check valve should be installed about 12" upward from the pump discharge outlet. In your situation, you will have to install another check valve on vertical pipe, right before it turns from vertical to horizontal.


The pump was installed last year and I remember the plumber saying that a check valve
Was installed. The plastic riser is about 7 feet up before it turns and goes across the
Basement to the outside. The place where I think the check valve is installed is about
3 feet up from the rectangelur sump pump hole. What is so strange is that there was
Never any problem until this last heavy rain (flooding) occurred. It does make the bumping noise after it has drained the hole probably 4 or 5 times. It sounds like a thud.
So far everything you have said makes sense to me.

That thund is the weight of the column of water trying to fall back into the pit, hitting the check valve. You could try a different check valve or moving the existing on high on the riser, this would lessen the weight of the water.

Ballenberg1: I like your version lot better:D

How do you finally resolve this matter. The thumping sound is leaving me with many sleepless nights.

Disturbedsleep: you install check valves...

I have the same problem, sump pump is four years old and never made this noise before. After discharge then comes the thud thud thud, usually about 7 thuds.
I thought because it was after the discharge it must be the check valve, and it the above posts seem to think that also. I also thought the check valve should be closer to elbow and I saw that comment also. The web is great to be able to ask and receive.

Thanks to those that have answered