Water dripping from a split AC: the drain, the ice and the monsoon

Updated · Claude AC · 2 sources cited

Contents (6)
  1. How much water are we talking about?
  2. The five causes, in the order they are checked
  3. What you can safely do yourself
  4. Monsoon: why dry mode helps, and why it is not a cure
  5. What a repair should involve
  6. Frequently asked questions

An air conditioner is a dehumidifier that happens to cool. Every hour it runs, moisture from your room condenses on the cold evaporator coil, collects in a tray under it and leaves through a drain hose to the outside. Water dripping onto your floor or running down the wall almost never means the machine is broken — it means that water found an easier way out than the one the installer built for it. This guide follows the same order a competent technician does, from the cause that explains most call-outs to the one that costs real money.

How much water are we talking about?

More than most owners expect, and the amount depends far more on humidity than on temperature. A 1.5 tonne split removes roughly 5.2 kW of heat; in the coastal humidity of Mumbai or Chennai, a quarter to a third of that work is spent condensing moisture rather than lowering temperature. Converting that latent load at about 2,450 kJ per kilogram of water gives on the order of one and a half to two litres an hour — ten to fifteen litres across a night. In dry May heat in Delhi or Jaipur, the same machine may produce a trickle, because there is little moisture in the air to condense.

That single fact explains the most common complaint in Indian homes: the AC that behaved perfectly through April starts dripping in July. Nothing failed. The drain path that coped with half a litre an hour is being asked to carry four times as much, and a partial blockage that never mattered before now matters every evening.

The five causes, in the order they are checked

1. A blocked drain

This is the majority of cases. Dust that gets past the filters mixes with condensate into a sludge, and in a warm wet pipe a biofilm grows on top of it. The blockage usually sits at the tray outlet or in the first bend of the hose. The tray fills, overflows at its lowest edge, and water appears at one corner of the indoor unit — very often the side away from the pipe. A technician clears it by flushing the line, sometimes with gentle compressed air from the outdoor end. It is routine work and part of any serious service visit, which is one more argument for the pre-monsoon service described in our AC maintenance guide for India.

2. A drain pipe that does not fall continuously

Condensate moves by gravity alone; there is no pump in a domestic split. The hose must slope downwards over its whole length. Three installation habits break that rule: a loop of spare pipe left coiled behind the unit, a run that rises to clear a window frame or a beam, and a hose whose end is pushed into a bucket or a drain and sits below standing water. Each creates a water trap that eventually backs up. A leak that begins within days of a new installation is nearly always this, and it is the installer’s job to correct — not a paid repair.

3. An indoor unit that is not level

The indoor unit is not mounted perfectly horizontal: it carries a slight tilt towards the drain side so the tray empties. If the mounting plate was fixed by eye, or if the wall plugs have loosened over years of vibration, the tilt can flatten or reverse. The symptom is a slow, persistent drip from one end, worse when the machine runs for hours. Re-levelling means taking the unit off its plate, which is a technician’s job.

4. A frozen coil that melts

If air stops moving over the evaporator, its surface drops below freezing and condensate turns to ice. When the machine stops, that ice melts far faster than the tray can drain and water sheets out of the front louvres — often with a sound of dripping inside the casing. The causes are a clogged filter, a fouled coil, a failing indoor fan, or a low refrigerant charge from a genuine leak. Ice on the copper pipes at the outdoor unit points to the last of these. Before anyone proposes a recharge, work through the checks that come before a gas refill: an AC that leaks water and cools poorly is usually telling you about airflow, not gas.

5. A cracked tray or sweating pipes

Least common, and worth naming so it is not missed. Plastic trays crack with age or during a careless cleaning; the drip then appears wherever the crack is, not at the tray edge. Separately, water that runs down the copper lines and appears where they enter the wall is not a drain fault at all — it is bare or crushed insulation on the refrigerant pipes condensing room moisture. Re-lagging the exposed section fixes it permanently.

And water at the outdoor unit?

In cooling mode the outdoor unit should stay dry, and a puddle under it deserves attention. In heating mode on a hot-and-cold model, the roles reverse: the outdoor coil condenses and defrosts, and water underneath it is entirely normal in winter.

What you can safely do yourself

Monsoon: why dry mode helps, and why it is not a cure

During the monsoon, outdoor air can sit above 80 % relative humidity for days, and the machine spends most of its energy pulling water out of it. Running dry mode reduces the room’s moisture with less overcooling, as explained in our guide to what the water-drop button really does — but it does not reduce the volume of condensate that must leave through the hose. A drain that is marginal in June will fail in July whatever mode you select. Clear it before the rains, not during them.

What a repair should involve

A drain complaint is low-skill, high-frequency work: flushing the line, cleaning the tray, checking the fall of the pipe and the level of the unit. Charges sit in the same indicative band as a routine service, and clearing the drain is normally included when a full service is being done anyway. Two proposals should make you pause: a refrigerant recharge offered for a water leak, and a replacement indoor unit for a cracked tray, which is usually a spare part. If cooling has genuinely fallen away as well, read when a gas refill is actually needed before agreeing to one.

Frequently asked questions

Why does my AC leak only at night?

Because a long unbroken run produces the most condensate and gives a partially blocked drain time to back up, while a short daytime cycle drains between stops. Night humidity is also higher in most Indian cities. The pattern points to a restricted drain rather than a failed part.

Is water leaking from an AC dangerous?

The water itself is condensate, not refrigerant, and is not toxic. The risks are indirect: it reaches wiring and wall sockets, it soaks plaster and grows mould, and a standing tray breeds mosquitoes. Switch the unit off at the breaker and get the drain cleared rather than living with a bucket.

Can a water leak mean low gas?

Indirectly, yes. Low charge makes the coil run colder than designed, ice forms, and the melt overwhelms the tray. But a filter that has not been washed in a year produces exactly the same symptom, and it is far more common. Airflow is checked first for that reason.

Should the drain pipe end in the open or in a drain?

In open air, with a clear gap above whatever receives the water. A hose pushed into a drain pipe or submerged in a bucket forms a water seal, backs up into the tray and can also let smells and insects travel up the line.

My new AC started leaking within a week. Who pays?

The installer, in almost every case. Early leaks come from pipe fall, unit level or a hose left coiled — all installation work, all covered by the installation warranty. Call whoever mounted it before calling anyone else, and read what a proper split installation includes so you know what was owed to you.

Sources

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