A/C Unit Water Problem
AC System =Compressor Unit (Outside) + Blower Unit (Inside)
1) Attic
2) Basement
Compressor unit / Blower unit together in Basement
(Residential)
Compressor unit/Blower unit together on Roof Top(RTU)
(Commercial)
Common Reasons an A/C Unit Overflows with Water
- Clogged Condensate Drain Line
As your A/C runs, it removes humidity from the air, which turns into condensation (water).
This water is supposed to drain outside via the condensate drain line.
If the line gets clogged with dirt, mold, algae, or debris, water backs up and can overflow into the house, often causing ceiling stains or water damage.
- Cracked or Rusted Drain Pan
The drain pan collects condensation under the evaporator coil.
Over time, it can rust or crack, especially in older units.
This causes water to leak instead of draining properly.
- Condensate Pump Failure
If your A/C is in a basement or far from a natural gravity drain, it may rely on a pump to move the water out. If the pump fails, water collects and spills over.
- Dirty Air Filter
A dirty filter restricts airflow over the evaporator coil.
This can cause the coil to freeze, and when it melts, it releases excess water all at once, which can overwhelm the drain system.
- Excess Humidity or Overuse
During very humid weather, the system may produce a large volume of condensation.
If the drainage is even slightly slow, this can cause overflow.
When to Check
– Before summer starts
– Mid-summer if you run A/C constantly
– Anytime you see water spots or leaks around the ceiling or A/C unit
