Why Your Aircon Drips Water in St Francis Bay, and How to Fix It

Where the water comes from

When an aircon cools a room, warm, moist air passes over the cold indoor coil. Moisture in the air condenses on the coil, just like water forms on a cold glass on a hot day. That water drips into a tray under the coil and flows out through a small drain pipe to the outside.

In a dry inland town, an aircon might produce a little water on a hot day. In a humid canal home in St Francis Bay, it can produce a lot, sometimes several litres a day. The drain system has to handle all of it. If anything slows the flow, the tray overflows and water drips out of the indoor unit.

Cause 1: A blocked drain

This is by far the most common cause. Over time, dust from the air, bits of mould and a slimy biofilm of algae and bacteria build up in the drain tray and pipe. In the warm, damp conditions inside an aircon, this growth is fast. Eventually it blocks the drain.

Signs: Water drips from the bottom or front of the indoor unit, often worse after running for a while. No water comes out of the drain pipe outside.

Fix: A technician clears and flushes the drain tray and line and can treat it to slow regrowth. Regular servicing prevents it from building up.

Cause 2: Poor drain slope

Water only flows downhill. If the drain pipe rises at any point, sags between supports or runs too flat, water sits in it. Sitting water encourages slime growth and eventually backs up into the tray.

Signs: Repeated leaks even after the drain has been cleared.

Fix: Re-route the drain line so it falls continuously to the outside.

Cause 3: A frozen coil

If airflow over the indoor coil is restricted by dirty filters, or if the system is low on refrigerant, the coil can get so cold that the condensation freezes into ice. When the unit switches off or the ice melts, a large amount of water comes off at once, more than the tray and drain can handle.

Signs: Ice visible on the indoor coil or the pipes at the outdoor unit. Weak airflow. Leaks that come in bursts.

Fix: Clean the filters. If it still freezes, have the gas checked for a leak.

Cause 4: An unlevel indoor unit

The drain tray is designed to drain towards one side. If the indoor unit was installed tilted the wrong way, water collects at the wrong end and overflows.

Fix: Re-level the indoor unit.

Cause 5: Condensation on pipes

On very humid days, poorly insulated refrigerant pipes can sweat, and that water runs back along the pipe and drips inside.

Fix: Replace or repair the pipe insulation.

Why it matters in St Francis homes

Water damage in a St Francis Bay home can be expensive. Many homes have reed or thatch ceilings, timber floors, built-in cupboards and soft furnishings that do not cope well with water. Stains on white walls are hard to remove. In holiday homes, a leak can go unnoticed for days.

What to do when it drips

1. Switch the aircon off. 2. Put a towel or container under the unit. 3. Check the filters and clean them if dirty. 4. Check outside: is water coming from the drain pipe? 5. Look for ice on the indoor coil or pipes. 6. If the filters are clean and it still drips, call a technician.

Do not keep running a leaking aircon. Water can reach electrical points and damage walls and floors.

Preventing leaks

• Service every six months in canal and waterfront homes, including drain flushing.
• Clean filters monthly during heavy use.
• Check the drain outlet occasionally to make sure water is coming out when the unit runs.
• Make sure the drain discharges correctly to a garden bed, gravel or drain, not onto a wall, deck or walkway.
• Run the unit monthly in holiday homes so the drain does not dry out and crust over.

Holiday homes

In homes that stand empty, drain slime can dry into a crust that blocks the line the first time the unit runs again. If you arrive for the holidays and the aircon starts dripping, this is the likely cause. A pre-season service in October or November flushes the drain before you need it.