The short answer
A mini split condensate pump moves water the drain can’t carry downhill on its own. Ceiling cassettes have one built in, and wall heads on an inside wall often hide a small one in the line cover. When it fails, water drips from the head, or a float switch shuts the head off and shows a drain code. In Northern Virginia that shows up in cooling season, because a head only makes water when it cools or dries the air. Clean the filters, check where the pump’s line ends, and call if the head still drips or the code comes back.
Who has a pump
- Ceiling cassettes. The pump and a float switch are built in, because the water has to rise out of the ceiling before it can drain. Daikin’s cassette manual allows a lift of just under 25 inches, within about a foot of the unit.
- Wall heads that can’t drain downhill. A head on an inside wall, or one whose hose would have to run uphill, gets a small pump, usually tucked in the line cover beside the head.
- Ducted and floor units in a basement or attic where the drain has nowhere lower to go.
A wall head on an outside wall with its hose sloping straight down through the wall has no pump. If that’s yours and it drips, mini split leaking water is the better read.
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Signs the pump is failing
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| What you see | Usually why | What to do |
|---|---|---|
| Water dripping from the cassette grille or the head | The pump stopped, or its line is clogged | Turn it off and call |
| The head shuts off in cool mode and shows a drain code | The float switch tripped because the pan is full | Don’t keep resetting it. Call |
| A hum or a gurgle with no water leaving | The pump runs, but its line is kinked or clogged | Check the outside end. If it’s clear, call |
| A pump that runs and runs | A stuck float, or a pan that never empties | Call. A pump that never rests wears out fast |
| A sour smell from the head or the line cover | Slime sitting in the pump’s reservoir | The pump and line need cleaning |
| Water in the line cover or on the wall under it | The pump or its tubing leaks | Call |
Drain codes by brand
Most heads with a pump also have a float switch. When the water rises, the float trips and the head shuts off before the pan spills. That’s the code you see.
- Mitsubishi Electric: P5 is the drain pump and P4 is the drain sensor or float switch. On a Mitsubishi cassette, the float sitting in water for about a minute and a half shuts off the compressor and the fan.
- Daikin: A3 is drain level control. The float stays up for 5 seconds, the head stops cooling, the pump runs 5 more minutes to try to clear it, then the head shows A3.
- LG: CH04 means the float switch tripped and the drain pan is full. LG says to switch the breaker off for 5 minutes, and if it comes back, stop using the unit.
- Samsung: 665 points to the drain pump.
The makers list the same causes behind every one of these: the pump, a clogged pump or pipe, or the float switch itself. Brand by brand: Mitsubishi, Carrier, Daikin, Fujitsu, LG, Samsung and MrCool, Pioneer, Gree and Senville. Every code family we’ve written up is on our error codes and warning lights page.
Why pumps fail
- Slime and dust. The pump’s reservoir collects whatever washes off the coil, and in time it gums up the float or the pump inlet.
- A kinked or sagging line, so the pump runs but the water doesn’t leave.
- A buried or frozen outlet. The end outside can sit in mulch or freeze shut, and the water backs up.
- A worn pump. It runs every time the head makes water, and the motor wears out.
- Power. A pump that loses power from a loose wire stops cold, and the float shuts the head off.
What you can check safely
- Turn the head off so it stops making water.
- Clean the filters. Dirty filters let the coil ice up, and the melt can swamp a pump.
- Find where the pump’s line ends, outside or at a drain, and make sure it isn’t buried, kinked or frozen.
- On a cassette, look for water stains on the ceiling around it.
- Turn it back on in cool or dry mode and listen for the pump. If the code or the drips come back, call.
Don’t open the cassette, bypass the float switch or pour cleaner into the pan. The float switch is the only thing standing between a dead pump and a wet ceiling, and pump makers say to wire it in for exactly that reason.
Keep it from happening
Have the pump and drain looked at before cooling season, when the heads start making water again. A ductless tune-up is $99 per system, the same price as a furnace or AC tune-up, and anything it finds that needs more gets a written price before any work. Our tune-up page has the details, and how to clean a mini split covers what you can do between visits.
Book it
A mini split visit starts with our $99 diagnostic, and you get the repair price in writing before anything is opened. Call (703) 997-9757 or book a visit online and tell us the brand and the code or what you’re seeing. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Mitsubishi Electric, Carrier, Daikin, Fujitsu, LG, Samsung, MrCool, Pioneer, Gree and Senville are trademarks of their owners.
Questions people ask
Does my mini split have a condensate pump?
Ceiling cassettes do, built in. A wall head has one when its drain can’t slope downhill outside, usually tucked in the line cover. A head on an outside wall with its hose straight through the wall usually doesn’t.
How do I know if my mini split condensate pump is bad?
Water dripping from the head, a drain code like P5, A3 or CH04, a pump that hums with no water leaving, or one that runs and runs.
Can I bypass the float switch to keep my mini split running?
No. The float switch shuts the head off before the pan overflows. Bypassing it trades a code for water in the ceiling or the wall.
Why does my mini split only leak in summer?
The head only makes water when it cools or dries the air. In heat mode the indoor coil is warm and stays dry, so a weak pump hides all winter.
How often should a mini split condensate pump be cleaned?
Once a year before cooling season, or sooner if it smells sour or gurgles. A dusty room or pets can mean more often.
