Why Is My AC Leaking Water? Causes and Solutions for Phnom Penh Homes

Water dripping from an air conditioner is one of the most common calls we receive from Phnom Penh homeowners — and one of the most misunderstood. It looks alarming. Water is running down the wall, pooling on the floor, or soaking into the ceiling below. But in the vast majority of cases, an AC leaking water is a maintenance problem rather than a mechanical failure, and catching it early makes it straightforward to resolve.

Understanding why your unit is leaking helps you judge how urgent the situation is and what the fix actually involves.

Why AC Units Produce Water at All

Air conditioners cool a room by drawing warm air across a cold evaporator coil. As warm, humid air contacts the cold coil surface, moisture condenses out of it — the same way a cold drink forms water droplets on the outside of the glass in Phnom Penh's humidity. This condensation drips into a drain pan directly beneath the coil and exits through a drain line to the outside.

Under normal operation, you won't see any of this water. It moves through the system efficiently and exits without issue. When you do see water, it means something in that drainage pathway has broken down.

The Most Common Cause: A Blocked Drain Line

The single most frequent cause of AC water leaks in Phnom Penh is a blocked or partially blocked condensate drain line.

The drain line runs from the indoor unit through the wall to a discharge point outside. In Phnom Penh's climate — high humidity, warm temperatures year-round, units running eight to twelve hours daily — algae, mould, and sludge build up inside the drain line faster than anywhere else. Over time, this organic buildup restricts the line until water can no longer drain freely. It backs up into the drain pan, overflows, and drips from the indoor unit.

The signs of a drain blockage are usually clear: water dripping steadily from the front or bottom of the indoor unit, often regardless of how cold the room is or how hard the unit is working. In some cases you'll notice a musty smell before you notice the drip — the standing water in the blocked pan has begun to breed bacteria and mould. If that's your situation, our guide to why your AC smells and what each odour means explains how a sewage or sour smell specifically often traces back to drain system issues.

A clear drain line is a standard part of any thorough professional service, and in Phnom Penh's conditions it's one of the tasks that matters most. Our guide on how often to have your AC cleaned in Cambodia reflects this — the recommended three to four month interval for heavily-used units is partly driven by how quickly drainage systems accumulate organic buildup in tropical conditions.

A Dirty or Frozen Evaporator Coil

If the drain line is clear but water is still leaking, the evaporator coil itself is often the culprit.

When a coil becomes heavily coated with dust and debris, airflow through the unit drops. With insufficient airflow across a coil that's still running cold, the coil surface temperature drops below freezing and ice begins to form. This isn't immediately visible from the outside — the ice builds up inside the unit. When you eventually switch the unit off (or when it cycles into defrost), that ice melts rapidly, producing more water than the drain system can handle and causing an overflow.

You may notice the leak is worse immediately after the unit turns off, or after running for several hours — both consistent with ice melt rather than a simple drain overflow.

A frozen coil is a serious warning sign beyond just the water. It means the system has been running in a significantly degraded state — typically because the filter is heavily clogged, the coil is dirty, or both. Our guide to the signs your AC needs cleaning covers ice formation in detail, including why it happens and what happens if you keep running a unit that's icing up. The coil and blower need to be properly cleaned — not just the filter — to resolve this properly.

A Cracked, Rusted, or Overflowing Drain Pan

The drain pan sits directly beneath the evaporator coil. In older units, or in units that have had standing water sitting in them for extended periods, the pan itself can crack, corrode, or become deformed. Water then leaks through the pan rather than out through the drain line.

This is less common in newer units but worth knowing about if yours is several years old and has had recurring drainage issues. A technician can inspect the pan visually and confirm whether it needs to be replaced.

In units where the drain line is partially but not fully blocked, the pan may also overflow during periods of peak condensation — a very hot day, a room full of people, or an extended run at high capacity — even if it's been managing adequately during normal conditions. In Phnom Penh, this situation often surfaces during the hot season peak from March through May, when condensation volumes increase sharply and marginal drainage systems are pushed past their limit.

Incorrect Installation or Insufficient Tilt

Less common but worth mentioning: if a unit was installed without the correct slight downward tilt toward the drainage side, water may not flow naturally toward the drain outlet. Instead, it pools on the wrong side of the pan and eventually overflows.

This is typically a problem that shows up shortly after installation rather than developing over time, though vibration and settling over years can occasionally shift a unit's alignment. If your unit has been leaking since it was installed, or if it developed a leak after significant vibration (construction work nearby, for example), installation tilt is worth checking.

Refrigerant Leaks and Dirty Coils: A Related Pattern

A refrigerant leak causes the evaporator coil to run colder than intended — sometimes cold enough to freeze over at lower ambient temperatures or when airflow is only mildly restricted. If you have a unit that's both leaking water and not cooling as effectively as it should, and you notice a faintly sweet or chemical smell, a refrigerant leak alongside a dirty coil may be the combined cause.

Reading the error codes on your unit can help here — modern inverter units from Daikin, Mitsubishi, LG, and Samsung will often flag refrigerant pressure faults with a specific code before performance degrades noticeably.

What Happens If You Ignore a Water Leak

A slow drip seems like a minor nuisance. Left unaddressed, it tends to become something more significant.

Water running behind the wall panel or into the ceiling damages building materials over time. Phnom Penh apartments — particularly older buildings — often have wall structures that absorb moisture readily, and the damage from months of slow leaking can be extensive and expensive to remediate. The standing water in the drain pan also creates a secondary mould colony inside the unit, compounding the air quality problem and making the eventual service more involved.

The broader principle applies here too: extending your air conditioner's lifespan in Cambodia relies heavily on catching problems when they're still in the maintenance category. A blocked drain cleaned at the first sign of a drip is a straightforward task. A unit that's been dripping for three months, with water-damaged walls, a corroded pan, and an established mould colony inside, requires significantly more work.

What to Do When You Notice a Leak

Stop running the unit if water is dripping significantly or if you suspect ice is forming. Continuing to run an icing unit compounds both the water damage and the mechanical wear.

Check the filter immediately. Pull it out and look at it. If it's heavily clogged with grey dust, that restricted airflow is likely part of the problem. Remove and clean it before doing anything else. Our DIY AC cleaning guide covers the correct filter cleaning process — it's straightforward and takes ten minutes.

Look at the drain discharge point outside. If water isn't flowing from the outdoor drain point while the unit is running, the line is blocked. This confirms a drainage issue rather than something more complex.

Book a professional service. Even if cleaning the filter seems to improve things temporarily, a technician should clear the drain line, inspect the coil, and check the drain pan. A drip that was suppressed by cleaning the filter hasn't fixed the underlying drainage accumulation — it's reduced the condensation load enough to stay below the blockage threshold, at least for now.

Prevention: The Most Practical Approach

The best approach to AC water leaks in Phnom Penh is preventing them from developing rather than waiting for the drip to appear.

Drain line clearing and pan inspection are standard elements of a professional AC service — not optional extras. On the three to four month service schedule appropriate for Cambodia's conditions, drainage systems rarely reach the point of complete blockage because they're being cleared before buildup gets that far. Our AC maintenance checklist for Cambodia includes drainage checks as a regular task alongside filter cleaning and outdoor unit inspection.

The units in Phnom Penh that develop chronic drainage problems are almost always the ones being serviced once a year, on the assumption that the climate here is comparable to somewhere cooler and drier. It isn't. The organic buildup that causes blockages accumulates in weeks here, not months.

Keeping up with maintenance is the practical solution. A clean drain line costs nothing extra when it's part of a regular service. A water-damaged wall costs quite a bit more.

If your unit is currently dripping or has developed a new leak, contact AC Clean Phnom Penh to arrange a service. In most cases, a professional clean resolves the issue completely — and a same-week booking means catching it before the damage has a chance to spread.