Why is my aircon leaking water? Causes, fixes, and when to call

If your aircon is dripping water indoors, the most likely cause is a clogged drain line. When that diagnosis is confirmed, an aircon drain flush may fall within the $80-$130 guide range.

There are three other causes that look similar but need different fixes. This article walks through how to tell which one you're dealing with, what each one costs, and the safe things you can check yourself before calling anyone. The prices below are SparkFlow guide ranges reviewed on 31 July 2026; the final quote depends on diagnosis and access.

First — should you switch it off?

Switch the aircon off at the wall, then place a towel or bucket where you can do so without touching the unit's electrical parts. Do not keep running it to "see if it clears": a drain blockage, frozen coil or damaged pan can worsen and cause more water damage. Daikin's official troubleshooting guidance likewise advises stopping use when water leaks from the unit.

The four common causes

1. Clogged condensate drain line (most common)

The condensate drain is a small pipe that carries condensation water away from the indoor unit and out the building. Over months, sludge, mould, and bug debris build up inside it. When the drain backs up, water has nowhere to go, so it overflows out of the tray and drips out of the front of the unit.

How to tell: water is dripping from the front of the indoor unit, usually near the bottom. The unit is still cooling normally. It's often worse when humidity is high.

Cost to fix: $80-$130. We bring a vacuum and a flush kit, clear the line in 30 minutes, and the unit is dry within an hour. If the drain pan also needs cleaning out, that's included.

2. Frozen evaporator coil

Restricted airflow from a heavily clogged filter, dirt on the indoor coil or an indoor fan fault can cause the evaporator to ice over. Low refrigerant pressure from a leak can do the same. When the ice thaws (when the unit cycles off, or you turn it off entirely), all that meltwater overflows the drain pan at once.

How to tell: the cooling has been weak or inconsistentrecently. You may see frost or actual ice on the indoor coil when you open the front panel. Water leaks tend to happen in bursts, not as a steady drip.

Cost to fix: the $90-$150 guide range may apply to cleaning and drainage work, but a fan fault or refrigerant leak will change the quote. Switch the unit off, let a technician check why it froze, and repair that cause before restarting. Carrier's leaking-aircon guide confirms that dirty filters and low refrigerant can both freeze a coil and lead to water leakage.

3. Cracked or shifted drain pan

The drain pan is the plastic tray under the coil that catches condensation before it goes down the drain line. If the tray has cracked from age, or shifted loose during a previous service, water spills out the side instead of flowing into the drain.

How to tell: water is dripping not from the front but from the side or back of the unit. Sometimes you see water marks on the wall below or behind the indoor unit.

Cost to fix: $100-$160. The pan needs to be replaced or re-seated. Includes labour and a new tray if needed.

4. Drain line installed without proper fall

The drain pipe is supposed to slope downward continuously from the indoor unit to the outlet. If a previous install didn't get the fall right — common with DIY jobs or rushed installs — water pools inside the pipe instead of draining out, then eventually backs up into the unit.

How to tell: this is usually a longer-running problem. The leaking has been intermittent for months, and standard drain flushes don't fix it for long.

Cost to fix: $120-$200. We re-route the drain pipe with proper fall, or fit a suitable condensate pump if the route doesn't allow gravity drainage. The chosen solution still needs correct installation and normal maintenance.

What you can check yourself first

Before calling anyone, two quick checks that occasionally save you a service call:

Clean the filter. Switch the aircon off, open the front panel, slide the filter out, wash it under running water, let it dry, slide it back. If the filter was obviously dusty, let it dry fully and refit it. Do not restart a unit that is still wet, frozen or leaking; arrange an inspection instead. A heavily clogged filter can contribute to both a frozen-coil leak and weak cooling, which is why servicing your aircon on a regular schedule heads off most leaks before they start.

Do not climb onto an aircon ledge or reach outside a window to inspect the condenser. If leaking continues, the next step is to book an aircon servicing and repair visit.

What you should not do

A few things people try that don't help and sometimes make it worse:

• Don't pour anything into the drain line yourself. Bleach can damage the pan; vinegar can corrode internals. Use only what a service uses (vacuum + proper flush).
• Don't accept an aircon gas top-up as a generic water-leak fix. Low refrigerant can indirectly cause a frozen coil and thaw-water overflow, but the sealed circuit must be checked for a leak and repaired before recharge.
• Don't ignore it for more than a day or two. A small drip turns into a constant drip turns into water damage to your floor, ceiling, or whatever's below it.

Is it worth doing chemical wash at the same time?

Only if inspection shows the coil or blower has buildup that routine cleaning cannot remove. A blocked drain alone usually calls for drain clearing, not an automatic chemical wash. It helps to know what aircon servicing typically costs in Singapore before you decide.

That said, we won't push it unless the unit genuinely needs it. If the drain flushes cleanly and the coil looks fine, you don't need a chemical wash. We'll tell you on site.

How we quote

WhatsApp us a photo of the indoor unit, where the water is leaking from, and the brand and model. We'll usually be able to narrow down the likely source and give a guide price, but an on-site inspection is what confirms the fault.

Same-day service is often available for water leaks, subject to the schedule and the parts the confirmed repair needs.

The short version

Four common causes account for many indoor aircon water leaks:

Switch a leaking unit off. Cleaning a removable indoor filter according to its manual is a reasonable check; outdoor ledges, internal covers, drainage chemicals and refrigerant work are not DIY territory.