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TL;DR: is a duty cycle where a 1/4 HP submersible sump pump is repeatedly running for [3 minutes pumping wet, 12 seconds pumping dry, 4 minutes off] going to damage the pump appreciably?

Long version: I have a sump pump, but the float switch will not work with the hacky sump pit setup we have (unfortunately, we can't change that).

Last year, we ran the thing manually every couple hours and the basement flooded several times. It was awful.

This year, I (over?) engineered an automatic on/off solution with Home Assistant, a smart plug, and a moisture sensor. In short, based on the risk level (specifically weather/moisture detection), the pump runs a test to see if any water is pumped (I can tell with like 98% accuracy from the power draw whether it's running wet or dry), with an exponential backoff every time it runs without pumping water.

This means that, in the floodiest times, when it's actually pumping a lot of water but not just constantly running, it runs a test every ~4 minutes after it stops pumping and runs dry for 12 seconds every time. That is, it runs something like 3 minutes pumping wet, 12 seconds pumping dry, 4 minutes off. In the least floody times, it runs every couple weeks just to make sure there wasn't some weird rain-unrelated undetected water leak when the moisture sensor also wasn't working.

This is a 1/4 HP Everbilt UTA02510 sump pump, which we're using in "submersible" mode (not sure what the "non-submersible" mode is actually for, and we also couldn't get it to work anyway).

My question is this: is that duty cycle going to damage the pump appreciably?

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  • Consider asking for solutions to the float problem in your setup rather than this XY question.
    – isherwood
    Commented Jan 22 at 19:21
  • Any chance a float would work for determining if the pump is likely to run dry, rather than the amount of pumping that needs to happen? Also I would be very wary about a solution for flooding which depends on so many ingredients. There has to be a solution which makes the decision closer to the problem. If you've been depending on Home Depot for your solutions, look to a real plumbing supply company. There are electronic controls for pumps that can reliably sense a half inch of water. If there's water to pump, you can sense it and pump it only when it's there.
    – KMJ
    Commented Jan 22 at 19:30
  • See grainger.com/product/6PNV7 for a float switch.
    – popham
    Commented Jan 22 at 19:38
  • This is a place where the KISS principle really pays off .vs. Rube Goldbergian complex solutions with many potential points of failure, IMHO. External float switches exist. Use one...
    – Ecnerwal
    Commented Jan 22 at 20:04
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    both modes require that the impeller be in the fliud so non submersable (transfer pump) mode needs to be started with a siphon, priming, or some existing "head" to the pump - so this other mode would be totally unsuited for your application
    – Jasen
    Commented Jan 23 at 0:51

1 Answer 1

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In my experience with sump and shallow well pumps, a short dry cycle will not appreciably affect the pump's lifespan. 12 seconds isn't enough time for residual water to vaporize and allow heat buildup. I've seen well pumps run on dry wells for days and they've shown no significant damage to interior components.

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  • Thank you! Do you think well pumps are similar enough to use that as an approximation here, or might the size/usage difference be so great as to be irrelevant? I don't know much about (a) the failure mode of these pumps or (b) motors in general. Commented Jan 22 at 20:20
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    I haven't had a sump pump apart, but I suspect that they're similar in design, with a rotating, rigid, non-contact impeller. If they had a soft, flexible, contact-dependent impeller like an outboard motor this answer would be wrong.
    – isherwood
    Commented Jan 22 at 20:27
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    All three sump pumps I've inspected had the rigid impellers you describe.
    – Jasen
    Commented Jan 23 at 0:57

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