"Mystery" sump pump


One of the devices Sense has “discovered” I don’t think I actually have (that I know of) - a sump pump. The mystery device runs about 10x daily for an average of 30s each time. I’ve set it to notify me when it cycles on but I’ve yet to isolate. We’ve looked at the dishwasher (not yet discovered), washing machine (discovered), ice maker (are they discovered separately?), anything that draws water as a pump would and haven’t found the culprit. I was thinking hot water heaters (both are in the attic), but the pump use doesn’t match the pattern of water use.

What other common household devices could be candidates that I should be looking for? (My house is slab foundation, no basement, no lawn sprinklers). Thanks!


If you are on a slab, a sump pump is pretty unlikely. Note that sense has no idea about things like water flow, but generally can distinguish between pump motors and heaters….quite different patterns. How much power are you talking about?

Ice makers (heater and motor) are frequently discovered separately from the appliance itself, as are the defrost coils (heater only) in most refrigerators.

Do you by any chance have a fish tank?


Hi Andy:

Avg usage is 205w.

I have two fish tanks and actually thought of that… both have small pumps running continuously; neither tank seems to have a power signature or usage pattern that matches what Sense tells me.


Do you have a high efficiency gas boiler/furnace that uses a condensate pump to get rid of its combustion byproducts? Or are you in an area that’s using air conditioning this time of year and generating condensate from that?

How about a hot water recirculation loop pump?

Can you post a screenshot of the power meter while this device is running?


Good morning, PSWired:

I do have a high-efficiency gas furnace (Trane XL19i) with a condensate pump. Would that run independently (not in sync with) the furnace? Weather has been temperate, but haven’t used the A/C in probably 2 weeks.

Screenshot of house power meter or the Sense power meter?



The condensate pump should run (for the most part) while the furnace is running or shortly after a run cycle ends. The pump has a small reservoir that fills as condensate drains from the furnace, then a float switch turns the pump on to empty the reservoir once it’s full. So, the pump can run at any time that more condensate is being introduced to the reservoir.

A screenshot of the sense power meter that shows an interval when the mystery device was running would be helpful so that we can see the usage pattern, which sometimes has some clues in it.


I was thinking the same, but the run time and power draw seems high for a condensate pump. Most pumps that I’ve seen are in the 1/50th or 1/30th HP range. I’ve seen as big as a 1/5th, but that was commercial use with a gallon tank. I can’t imagine a 1/5 HP pump taking 30 seconds to empty condensation, let alone what size HVAC system is generating that much condensation.

But on the same page - @heavythink, does your septic system have a tank pump? Or does your HVAC system have a circulator fan, or exterior air exchange that runs automatically? Not a pump, but Sense could be confused. But as PS mentioned, if you can grab a screen from the device screen of the device when it turns on, that may help lead us all in the right direction.


You’re probably right about the power draw being too high for a normal residential condensate pump.


Perhaps the defroster coil in your refrigerator freezer freezer? Does it seem to run on a set schedule or is it somewhat random?


No septic tank. HVAC with exterior 2-stage compressor. Not sure which screenshot you’re requesting so I’ll start with this… let me know if this isn’t what you’re looking for.



Hi. Sorry. I could have been clearer.
If possible, on an iPhone/iPad/Android device using the app (vs web site) if you go to the device tab, and then scroll down, you should see the power meter for the last 24 hours.
Tap into that. Then if you side scroll until you find an instance of the pump turning on.
Then lastly, “pinch” to zoom to try to get the time scale small so that we can see in detail the start up spike and what the power signature looks like.

See attached as an example. Note the time across the bottom is only about 1 minute, so you can see in detail what the initial spike looks like.


Good morning, Ben:

Here are the last two instances (captured from my iPad) of this device cycling on. I’ve drilled in and expanded both signatures, neither of which lasts for more than 30sec or so.

Thanks… and let me know if I need to send something further.