Electric sump pump sometimes fails to engage / kick on

Question

I have a sump in my basement that collects water from (I believe) outside of the house through some kind of foundation drain / weeping tile.

Lately with all of the snow melting and rain, I've noticed that the electric sump pump is not always kicking in on its own. Sometimes it does, but often I hear the backup (water-based) pump instead.

I've taken a look down the sump and it looks like the float for the switch is rising but still isn't engaging the pump. If I gently jiggle the discharge pipe, it kicks right on.

See this video, with the electric sump pump in the bottom-center of the frame (green) and the white float right above it (note the water level is already at/above the float): https://vid.me/IM6i

The float seems to rise but at some point, the water level rises over it. Could the float be waterlogged, so it does not have enough buoyancy to engage the pump? Or could it be something with the rod that connects the float to the pump? Why does it happen intermittently?

How should I go about investigating further?

Thanks for the help.

Answer 1

The float should travel freely up and down on a vertical rod.

As the float rises toward the top of its travel, it operates a switch. This is the switch that turns on the pump.

Raise the float manually. The switch should operate and the pump should turn on. If it does not, it is the power supply, the switch or the pump.

It should be obvious just by looking at the float whether it is floating or not.

Answer 2

A waterlogged float will be audible if you remove it from the pump and shake it.

IMPE the rod/top mount motor arrangement is often subject to flaky operation as some part of the mechanism binds, sometimes, not always, just enough to prevent it from turning on.

I have found fully submersible sump pumps far more reliable, but my workplace still chooses the cheapest pumps with the top motor, which can be expensive when you count the cost of the occasional flood. But that's why I'm familiar with their issues. The fact that "jiggling" causes it to work suggests (to me) binding in the float mechanism or a defective switch, and binding is far more common.

If the pump is not vertical or the rod-support is not lined up with the switch properly, the odds of binding increase. Check the float/rod system for free and easy movement (manually) and adjust as needed. Test with a hose or a bucket of water, adding water to the sump to check turn-on. Or take the more expensive road and get a submersible sump pump to replace it.