An indoor AC unit that drips is usually dealing with condensate that can't drain away: a clogged drain line, a coil that froze because the filters are dirty, or a unit or drain hose that isn't sloped correctly. Shut it off, catch the water, clean the filters and check the drain line before you call for service.
Why an AC makes water at all
When warm, humid room air crosses the cold indoor coil, moisture condenses on it, the same way a glass of iced tea sweats in July. That water drips into a pan under the coil and runs out through a small drain hose, either by gravity to the outside or into a condensate pump.
So water itself is normal. Water coming out of the front of the indoor unit, running down the wall or dripping from the louvers is not. Trane also points out that a mini-split shouldn't leak in heat mode, since the indoor coil is hot then. A drip in winter needs a closer look.
First, stop the damage
Turn the unit off with the remote. If water is running down the wall near an outlet, a cord or the unit's power connection, switch the system off at the breaker and don't touch the plug. Samsung's leak guide says to cut power at the breaker before you inspect anything, since water conducts electricity.
Put a bucket or towels under the drip and move furniture and electronics out of the way. If there's a code on the display, photograph it before you shut the unit down.
Clean the filters and let a frozen coil thaw
Dirty filters cut airflow over the indoor coil, and the coil can drop below freezing and grow a layer of ice. When that ice melts, it can overflow the drain pan. Carrier and Trane both list dirty filters as a cause of mini-split leaks.
Open the front panel and look at the coil behind the filters. If you see frost or ice, leave the unit off with towels or a bucket underneath until it has melted completely. Trane warns that running a mini-split with a frozen coil can damage it. Then pull the filters, clean them, and dry them fully before you put them back. Our mini-split filter guide has the details.
Several brands flag the freeze directly: Daikin's A5, Gree's E2 and Mitsubishi Electric's P6. If the coil keeps icing with clean filters, low refrigerant is the likely cause, which is a technician job.
Check the condensate drain line
Carrier calls clogged drain lines a major cause of mini-split leaks. Dust and slime build up in the small hose until water backs up into the unit and spills out. Carrier adds that a musty smell can mean water has been sitting in the line.
Follow the drain hose from the indoor unit to where it ends, often outside near the foundation or at a condensate pump. Make sure the end isn't buried in mulch, crushed, or sitting in a puddle, and look for kinks along the way.
If you can reach the end, Carrier suggests a wet/dry vac to pull debris out of the line. Hold the vacuum hose tight against the drain end and run it for a minute or two. Don't pour bleach or drain cleaner into the line. Samsung also says to look over the hose for cracks and replace a damaged one. A clog you can't reach, or one inside the unit, needs a technician to open the indoor unit.
Check the condensate pump, if you have one
When the drain can't run downhill to the outside, a small pump lifts the water out. Some ceiling and ducted units have the pump built in. When the pump or its float stops working, the pan fills up.
Units with a float switch shut down and show a code before they spill. Daikin's A3, Fujitsu's 53, Gree's E9, LG's CH04, Mitsubishi Electric's P4, P5 and PA, and Samsung's E153 and E665 all relate to a float switch, drain pump or water level in the drain pan. An external pump that hums without moving water, or has water sitting in its reservoir, is clogged or failed. Unplug it before you open the reservoir to clean it.
Check that the unit and drain are sloped correctly
The indoor unit has to sit correctly so water runs to the drain outlet, and the drain hose has to run downhill the whole way. Carrier gives a minimum slope of 1/100, about 1/8 in per foot (1 cm per meter). A hose that sags or rises anywhere traps water. Trane says an indoor unit tilted forward can overflow and drip, or push water out through the vents, and that installation problems like this are more common with DIY installs.
If the unit looks visibly crooked, or the leak started right after it was installed, call the installer. Re-hanging the unit means working around the refrigerant lines and wiring behind it.
Damaged drain pan or refrigerant problems
On older units the drain pan can crack or rust through. Trane and Carrier both say a cracked or corroded pan should be replaced by a professional.
Low refrigerant shows up here too. Trane and Samsung both link a low charge to ice on the coil, and the meltwater leaks. Refrigerant doesn't get used up, so a low charge means there's a leak somewhere. Codes like Daikin's U0, LG's CH38 or Samsung's E554 point that way. Only an EPA Section 608 certified technician can find the leak and recharge the system.
When to call a professional
Call an HVAC technician if the leak continues after you've cleaned the filters and cleared the end of the drain line, if the drain pan is cracked, or if the unit isn't level. Repeated coil freezing with clean filters, or any low-refrigerant code, needs an EPA 608 certified technician. If the system is still under warranty, Trane advises having a professional do the drain work so the warranty isn't affected.
Parts involved
- Condensate drain line and pan
- Condensate pump and float switch
- Air filter
- Refrigerant charge and line set
Error codes for this problem
- A3Condensate water level too highDaikin
- 53Drain pump errorFujitsu
- E9Condensate overflow protectionGree
- CH04Drain problem or water tank fullLG
- P4 / P5Drain sensor or drain pump problemMitsubishi Electric
- PAShut down to prevent a water leakMitsubishi Electric
- E153 / E665Drain pump or float switch problemSamsung
- A5Freeze-up or overheat protectionDaikin
- E2Indoor coil freeze protectionGree
- P6Freeze or overheat protectionMitsubishi Electric
- U0Low refrigerant or restricted refrigerant flowDaikin
- CH38Low refrigerant protectionLG
- E554Refrigerant leak or low refrigerantSamsung
- EL 0CPossible refrigerant leak detectedMidea