AC Drain Line Clogs and Ceiling Leaks

As warm indoor air passes over the cold evaporator coil, moisture condenses into water. It drips into a pan under the coil and flows out through a small condensate line, usually to the outside or into a drain. In a long cooling season, that line runs nearly every day.

Dust, pet hair and algae grow in the warm, wet line. Over time they form a slimy clog. When the line backs up, the pan fills and overflows. If the unit is in the attic, the overflow soaks insulation and the ceiling below. If it is in a hall closet, water runs under the closet wall into the next room.

Water on the floor of the AC closet, drips from a ceiling vent, a stain on the ceiling under the attic unit, the AC shutting off because a float switch tripped, or a musty smell when the system runs.

Many HVAC companies suggest pouring a cup of white vinegar into the condensate line's access port each month in cooling season to keep algae down. Check that the outside end of the line drips when the AC runs; if it does not, the line may be blocked.

A float switch shuts the AC off when the pan fills, preventing an overflow. Attic units should also have a secondary pan under them with its own drain or switch. Ask an HVAC technician to check both during a tune-up.

Older metal drain pans rust through. Water then leaks straight through the pan onto the ceiling. A technician can replace the pan or add a secondary pan.

Turn the AC off at the thermostat, catch drips, photograph and call. An HVAC technician clears the line; a restoration provider dries the ceiling, closet floor and walls. See AC and water heater leaks.

Attic insulation and closet drywall soaked by condensate can grow mold because they stay dark and damp. Dry them quickly and replace wet insulation.

In many single-story homes the air handler sits in a hall closet. When the pan overflows, water runs under the closet door and walls into nearby rooms. Swollen baseboards in the hall or wet carpet in a bedroom next to the closet are common signs.

Some systems use a small pump to move condensate to a drain. If it fails, water overflows. A pump that hums without emptying, or water around it, means it needs replacing.

A spring tune-up by an HVAC technician should include clearing the drain line, checking the pan and testing the float switch. It costs little compared with a ceiling repair.

In rentals, put the condensate line on the yearly maintenance list. Tenants should report any water near the AC closet right away.

Once the drain line is fixed, wet attic insulation is removed and the ceiling below is checked. Sagging drywall is replaced; stained but sound drywall may dry in place and be sealed and painted.

Before a long summer trip, have the drain line flushed and the float switch tested. An overflow while no one is home can soak a ceiling for days.

Water dripping from a ceiling vent or around the AC closet? Turn the AC off and call (623) 269-9046.

Closets and attics that stay damp from slow overflows can grow mold on drywall and insulation. A musty smell when the AC runs is a reason to have the closet and ductwork checked.

Sudden overflows are often covered; long-term slow leaks may not be. Keep service records showing the system was maintained.

Ask your HVAC technician to clear the drain line during each service visit. Between visits, pour a cup of white vinegar into the drain access point near the indoor unit every month or two during cooling season. Check the pan under the unit for rust and standing water. A float switch that shuts the AC off when the pan fills is a low-cost upgrade that prevents ceiling damage. If water reaches a ceiling, turn the AC off and call (623) 269-9046.

A clean drain line and a working float switch prevent most AC ceiling leaks in Avondale homes.

A monthly flush, a working float switch and a yearly tune-up prevent most AC water damage.

Questions about ac drain line clogs and ceiling leaks? Call (623) 269-9046 to reach a local Avondale provider, 24 hours a day.