Key takeaways
A dripping air conditioner is usually caused by a clogged filter or a blocked condensate drain, not a major fault.
Where the water appears tells you the cause: the front face, the sides, the pipe, and the coil each point to a different problem.
Most filter and drain issues clear in about five minutes using fan mode.
A light drip is low risk, but water reaching the unit’s electrical parts means you should switch it off
Why is my air conditioner dripping water inside?
As it cools a room, an air conditioner pulls moisture out of the air. That water collects in a tray inside the indoor unit and runs outside through a thin drain hose. When something blocks that path, or chills a part of the unit it should not, the water escapes into the room instead and you see a drip. Bangkok’s humid air produces a lot of this water, so even a small blockage shows up quickly.
The quickest way to find the cause is to look at where the water appears. We call this the Drip-Point Test: match the spot to the cause, and you will know straight away whether it is a five-minute job or a call to a technician.
Where the water appears | What to do | What to do |
Water dripping from the front air outlet | A dirty air filter has caused the evaporator coil to freeze and then melt | Try cleaning the air filter first |
Water leaking from underneath the indoor unit | A blocked drain line or dirt buildup inside the unit | Clean the air filter first; if the problem persists, call a technician |
Water dripping from the left or right side of the indoor unit | The drain tray is loose, misaligned, or there is an internal issue | Call a technician |
Water running along the refrigerant pipe | Damaged or deteriorated pipe insulation | Call a technician |
Water dripping directly from the evaporator coil | Low refrigerant level or a cracked drain tray | Call a technician |
How do I stop a dripping air conditioner?
Work through these steps in order. They cover the two most common causes, a dirty filter and a lightly blocked drain, which between them explain most indoor drips.
Step 1: Switch the unit off at the wall or breaker. Cut the power before you touch the unit. This keeps you safe and lets any ice on the coil start to melt.
Step 2: Remove and rinse the filter. Open the front panel, slide the filter out, rinse it under plain water, let it dry, and refit it. A dust-clogged filter is the single most common reason a coil ices up and then drips.
Step 3: Run fan mode for 20 to 30 minutes. Set the remote to fan onlyม not cool. The fan melts any remaining ice and helps the drain clear, without making more condensation.
Step 4: Check the drain outlet outside. Find the small drain pipe that runs outside and clear any dust or slime from its mouth. A short, gentle blow through the pipe often shifts a light blockage.
Step 5: Set the temperature to 25 to 26°C. A very low setting in a humid room can chill the coil until ice forms, then melts and overflows the tray; many aircon unit manufacturers advise against running too cold for this reason. A setting of 25 to 26°C stays comfortable and lowers the risk.
Is it dangerous to keep using an air conditioner that leaks water?
A light drip is low risk; a heavy one is not. Water reaching the indoor circuit board is a short-circuit risk, and a leak left running can stain your ceiling and wall. If the drip is heavy or near the unit’s electrical parts, switch it off and work through the steps above first. Running fan mode to dry the unit is fine; running cool mode through a heavy leak is not.
When should you call a technician instead?
Call a professional when the cause is inside the unit itself, not the filter or drain. Three signs point that way: weak cooling with the outdoor unit blowing only ordinary air, which can mean the system is low on refrigerant gas; water from the coil even after a clean filter and clear drain, which can mean a cracked water tray; or a drip that runs along the pipework, where the insulation needs replacing. This kind of work is not a home job, so book a technician rather than open the unit yourself.
A professional clean also clears the two most common causes, a clogged filter and a silted drain line, before they turn into a drip. You can book a home aircon cleaning through gigit.