Air conditioner leaking water indoors: drain line, mounting angle and filter

• Close the main water valve before opening any water connection.
• Keep water away from sockets and plugs.
• Switch off the MCB and unplug the appliance before checking anything.
• Make sure your hands and the floor are dry.

The main water valve matters here if your AC's drain hose is connected to the house plumbing. Water from the indoor unit often drips right onto a socket or cable below it; if it does, switch off the MCB first.

When it cools, the AC chills the air passing over the indoor unit's evaporator. Moisture from the room air condenses on the evaporator fins, drips into a drain pan, then flows out through a hose to the outside. The Modena split AC manual even treats this drain water as a sign that the AC is working normally: once the unit produces water, the cooling system is running. So the water itself is not the problem. The problem starts when it does not flow where it should.

LG Indonesia's help page starts with the simplest checks. A filter clogged with dust disrupts the airflow, so small droplets can be blown out with the cold air and condensation forms near the air outlet. Next comes the drain path: the drain pump, if there is one, the direction of the hose, and the hose end.

In Indonesia's humid climate, an AC produces a lot of condensation, so even a partly blocked drain overflows quickly. The Modena manual also notes that algae can grow in the drain line and cause noise, especially if the pipe leads into an open gutter.

In the rainy season, water seeping through the roof or wall sometimes shows up right above or behind the indoor unit, so it is easy to mistake for a leaking AC. Before taking anything apart, look at the pattern. Water from the AC appears while it runs in cool mode and stops soon after it is switched off; the water is clear and cold. Seepage from the building appears during or after rain, leaves brownish stains on the wall or ceiling, and keeps coming even with the AC off.

A simple test: leave the AC off for a dry day and see whether the dripping stops. If it continues, the source is probably not the AC, and the person to call is a contractor or roofer.

1. Clean the filter. Switch off the power and unplug the cord, lift the front panel and remove the fine filter. Clean it with a vacuum cleaner or a soft brush; if it is very dirty, wash it with mild detergent. LG says the water should be no hotter than 40°C. Dry it in a shady, well-ventilated place until it is completely dry, then put it back. Some add-on filters must not be washed and need replacing regularly.
2. Follow the drain hose. Trace the hose from the indoor unit to its end. LG says the hose should run downward in a straight line without bends; a hose that rises or kinks sends water back into the unit.
3. Check the hose end. If the hose ends in a bucket, water jug or tank, make sure the end is not under water. LG explains that a submerged end makes water flow back into the unit; empty the container as often as you can.
4. Check the connections. If the hose has come loose or torn at a connection you can reach, LG suggests reconnecting it securely and wrapping it with electrical tape.
5. Drain pump. Where the installation uses a drain pump, LG says to have the pump's power supply and condition checked; leave this to a technician.
6. Room conditions. Running the AC with a window open on a rainy day, or while cooking in the room, creates large differences in temperature and humidity. LG says that in these conditions condensation can form near the air outlet, or white vapor can come out of the unit.

Condensate drains by gravity, so the indoor unit and its hose must be installed at the right angle. If a leak appears after the unit is first installed or moved, LG suggests having the installer check the installation again, including the drain hose and the drain slope. A typical sign is water dripping from one side of the unit, usually the side that sits lower than its drain path.

The Modena split AC manual gives some related installation rules. The indoor unit must be at least 20cm from the ceiling and from the wall. The manual advises against joining the drain pipe to a wastewater drain or running it into one, because the unit then quickly gets dirty with algae and draws in the sewer smell. In its troubleshooting section, the same manual says the drain pipe should not run over a household gutter or be combined with dishwater.

Judging the angle by eye is often misleading. If you suspect the unit is tilted or the pipe rises inside the wall, do not take the bracket apart yourself; note which side drips and tell the installer.

The Modena manual says to clean the indoor unit's filter and drain line regularly. For the filter, it suggests cleaning it whenever it looks dusty, within one or two months; for the drain line, what matters is that no algae or deposits narrow the water's path.

• Clean the filter more often in the dusty dry season, or if the house is on a busy road.
• Check the hose end outside the house after the rainy season; leaves, soil and insect nests can block it.
• Do not put a pot, bucket or anything else under the hose end where the end can end up under water.
• Leave washing the evaporator and drain pan to an AC service company, because it means taking the unit's housing apart and protecting the electrical parts from water.

One more thing to know: the Modena manual says that after a long time in cool or dry mode, dew-like water forms around the louver, and that this is normal. Just wipe it off; it is different from water that keeps dripping from under the unit.

Contact an AC technician or the authorized service center for your brand if:

• the leak started when the AC was newly installed or moved (LG suggests having the installer check the hose and the drain slope again);
• it leaks during normal use and the filter and the visible hose are fine (LG suggests having a service technician check it for an accurate diagnosis);
• water keeps flowing even with the AC switched off;
• water drips onto a socket, cable or electrical panel below the unit;
• a hose inside the wall or above the ceiling needs repair, or the hose has a sharp bend you cannot straighten yourself;
• the drain pump does not work.

Taking apart and washing the evaporator and drain pan, readjusting the bracket and the unit's angle, or replacing a hose built into the wall are jobs for a technician. If water has reached the electrical installation, have an electrician check it before switching the MCB back on.