Help! New homeowner here. We have a carrier minisplit in our bedroom, which works well. We live in a rowhouse (so two brick walls on the side), so a condensate pump is used to pump water onto the roof and to the back of the house. The problem is that the pump makes a loud buzzing sound every 1-2 minutes. Is that frequency normal?

The annoying part is that it does this even when the unit is turned off. I'm very new to this HVAC stuff but after doing some research, it seems like there's an issue with the float switch. What should I do? Get a new pump? The HVAC tech didn't seem like could help with this but I'm pretty useless with this level of DIY. I can't sleep with it buzzing constantly -- help!

  • Thanks, Ed! The minisplit filters are clean but I don't think anyone has cleaned the pump for awhile. I don't know how to do that. The pump is in a little white box-type thing (see? I'm very clueless with this stuff) and screwed shut. Should I open it up to take a look? Should I get a new pump?
    – Erin
    Apr 30, 2021 at 14:37

1 Answer 1


I can see the pump turning on a couple of times after being in cooling mode but it should not have a lot of water to pump once the unit warms up.

if the pump is pushing water I would be concerned about the amount of ice in the head.

Is the filter being cleaned low air flow can cause icing.

Don’t run the ac when the outside temps are below 65F this can cause icing.

If there is ice on the evaporator coil it may take several hours to melt and your pump is doing it’s job.

I would be concerned about that much ice, floats usually stick closed and won’t turn off or fail to close and turn the pump on.

I have not seen a float cycle unless it has to lift the water and then a long horizontal run. What happens in some cases the water is syphoned back into the pump.

A simple check valve close to the pump is needed in this case this theory is easy to check by watching the water level in the pump tray.

  • With the mini split off , no water in the drip pan that drains to the pump, add just enough water to get it to turn on. If it pumps out turns off then 1-2 minutes later turns on it is probably sucking the water back in the pipe and this could continue for hours, is hard on the pump and your sleep. A simple check valve will prevent this from happening.
    – Ed Beal
    Apr 30, 2021 at 17:15
  • Erin thanks are ok but on this site clicking on an up arrow or giving an answer a check mark shows others that have a similar issue this answer was helpful or accepted.
    – Ed Beal
    Apr 30, 2021 at 19:50

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