Why Is Water Dripping From My Indoor Air Conditioning Unit?

Where the water is supposed to go

Every air conditioning indoor unit produces condensate as it cools and dehumidifies the air passing over its coil. In normal operation this water collects in a drip tray and drains away quietly through a condensate pipe, either by gravity to an external point or via a small condensate pump if gravity drainage isn't practical.

When you notice dripping from the unit itself, or staining on the wall or ceiling below it, something in that drainage path has gone wrong rather than the unit somehow malfunctioning internally.

Blocked condensate pipes

The most frequent cause of dripping is a blocked condensate drain. Algae, dust and general debris can build up inside the pipe over time, particularly if it hasn't been serviced in a while, causing water to back up and overflow the drip tray instead of draining away.

This tends to develop gradually, so if a unit that has never dripped before suddenly starts, a blockage is often the first thing an engineer will check.

Condensate pump failure

Where an indoor unit is positioned somewhere that can't drain by gravity alone, a small condensate pump is fitted to lift the water away to a suitable discharge point. Like any mechanical pump, these can fail or become jammed with debris, and when they do, the water they'd normally move simply overflows.

A failed pump usually needs replacing rather than repairing, and it's a straightforward job for a qualified engineer during a service or fault-finding visit.

Incorrect installation angle

Condensate pipework relies on a continuous fall to drain properly. If a pipe was installed with an insufficient gradient, or has sagged over time, water can pool inside it rather than flowing away, eventually leading to a backup and overflow at the indoor unit.

This is one of the reasons installation quality matters just as much as the equipment itself. A rushed first fix can cause drainage problems that only appear months or years later.

Low refrigerant causing excess condensation

In some cases dripping is a symptom of a refrigerant issue rather than a drainage one. A low refrigerant charge can cause the indoor coil to run colder than intended, sometimes leading to ice formation that then melts and produces more water than the drainage system is designed to handle at once.

If dripping is accompanied by weaker cooling or ice on the pipework, this is worth flagging to your engineer specifically.

What to do if your unit is dripping

Switch the unit off if water is actively running down a wall or onto flooring, and place something underneath to catch drips while you arrange a visit. Avoid poking around inside the unit yourself, as indoor units contain electrical components and, in some cases, sharp coil fins.

Booking a repair

Diagnosis and repair of condensate issues should be carried out by a qualified engineer, since the fix depends entirely on the cause, whether that's clearing a blockage, replacing a pump, correcting a pipe run, or addressing a refrigerant fault. Appointments are subject to engineer availability, so it's worth reporting the issue as soon as you notice it rather than waiting for it to worsen.