I am an amateur, so ask all the stupid questions you need to.

I have a submersible sump pump in my basement. It mostly works; however, from time to time, I have to tap the switch housing (I don't know what else to call it. I mean the little box that appears to house the connection between the float/switch and, I'm guessing, the motor) in order for the pump to turn on. The float appears to move freely up and down, but, of course, I can't tell when I have to tap the switch housing whether the float also suddenly rises to engage the switch.

If I pull the float up by hand, the mechanism works fine. When I tap the switch housing, the pump successfully gets rid of all the standing water, even if that takes several minutes.

This pump is about 2-3 years old.

That's as much as I know to tell you up front. I'm looking for possible common causes, simple DIY tricks I can try to improve the situation, and signs that I might need to replace the pump. It appears to work in general, but, of course, I'd like it to be more reliable than this. Which seems more likely: the float is occasionally sticking and not rising and not engaging the switch or there is something loose between the switch and the motor that a light tap jostles just enough to make it work? or is there something else entirely I need to look at?

Update: I did some simple testing today, and the float appears to work well. I filled up the pit both quickly and slowly (with a hose pointed away from the float) and the float rose in the pit every time. I tried spraying some water at the underside of the housing where the float slides up, in case that knocked loose some dirt or muck that might have been occasionally getting in the way. When I let the pit fill slowly over several minutes, the float appears to rise and all seems well. Again---at least as much as my amateur eyes can figure out. I'm happy to take more suggestions for what to try, either to find the cause or to rule other causes out.

  • 1
    There's probably a relay in the housing that's sticky. Aren't you able to determine whether the float is rising?
    – isherwood
    Feb 7, 2018 at 14:59
  • More than likely is a bad float.
    – Tyson
    Feb 7, 2018 at 15:13
  • @isherwood The float seems to be rising, even with very slow water flowing into the pit. I added some details above; does that trigger any further ideas? Feb 7, 2018 at 17:14
  • 1
    Either the float switch or the relay it triggers. You'd have to do some closer inspection.
    – isherwood
    Feb 7, 2018 at 17:34
  • 1
    next time that it's not turning on, don't tap the pump first, first just lighty touch the float, second give the float a thunk. if you have to move on to the pump to get it to start then it might be a relay inside the pump--if on the other hand just an operation on the float puts you back in business then it's a bad float.
    – Tyson
    Feb 7, 2018 at 20:48

3 Answers 3


Most rod or lever actuated float switch mechanisms use a "snap switch" inside in order to avoid having the switch contacts "bounce" with the turbulence of the water on the float itself. Your snap switch may be corroded and sticking too long as the float mechanism rises against it, so when you tap it, you are freeing it. On most of them, those snap switches are replaceable and inexpensive.


There are 2 things I have found with floats controlling pumps of all sizes.

The first is corrosion and dirt buildup limiting float travel so the foot sticks and the contacts are open until tapped.

The 2nd is burned contacts. I have found with frequent cycling the contacts get pitted and may not close. On larger pumps the contacts usually can be cleaned but on the smaller pumps they are not serviceable. A tap on the pump many times will get the pump running for a while but once the contacts start failing a new switch will be needed.

Some pumps have provisions where the float has a cord and the pump has a cord. In this case a new float is can be installed.

  • Thank you. I hope it's not typically for these pumps to be effectively disposable. Sep 16, 2018 at 22:48

The pump itself may also be nearing the end of its usable life.

  • Thanks. I hope not; it seems like I need to replace these every 2-3 years, and that seems abnormally frequent from what I've gathered so far. Feb 9, 2018 at 15:19

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