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Buffalo, NY

Why won't my sump pump shut off?

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Lots of sump questions lately. Here is mine.

All of a sudden, my pump won't shut off. It drains the pit just fine, but then keeps running. If I lift the float up, it will shut off. Then I put the float back down and the pump kicks on as it should when the water level gets to a certain point, but then it just keeps running after it empties the pit.

Is something wrong with the float or switch? I haven't removed it yet to look at it as I wanted to bounce this off you folks first.

Here are some before/after pics and a 3rd one of me lifting the float with a golf club.

There does seem to be a lot of debris in the pit and I'm wondering if that's at least part of the issue. I will clean that out today too.

One last thing...when I lift the float, it appears to just be dangling there. I thought it was supposed to be attached to the pump somehow. I wonder if this is normal or did a screw come loose or something.

Bozeman, MT
You only have one float. My quick sketch shows a float in both positions.
I would say your float switch is not falling to the correct position to properly disconnect the power.

Depending on the age of the float, it might have mercury in it or it might be a mechanical switch.

Some older floats had the connection wires poking into a container with a bit of mercury in it. Mercury is electrically conductive. When the mercury is contacting both terminals, the pump will run. If the float isn't falling to straight down, the terminals may still be connected.

If your float has a mechanical switch, it might be sticking. There could be a weight on an arm that activates the switch when it is in the proper position. When you mess with the float, it un-sticks and shuts off until next time.


San Diego, CA
·Cox HSI

1 edit
reply to UglyDork
Some floats use a mercury type of switch and are meant to be free floating. If that is the case they should not have their movement restricted.

In picture #2 the float cord is stuck under the pump. I am pretty sure that float cord needs to be free floating and not have its movement restricted.

Buffalo, NY
Thanks guys. I took the whole unit out of the water, cleaned it up, and noticed the float was at one time was attached to the pump but had broken off. The broken piece was still attached to the float.

So, I assume that the pump wasn't shutting off because there was so much slack in the line.

I took a plastic tie and tied off the float to the PVC pipe so that only about 5in was available.

I plugged the pump in and filled it with water. The pump kicked on and off correctly.

Looks like I'll be taking the switch back to Home Depot tomorrow. Good thing too because they were more expensive than I'd thought they would be.