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Why Is My Central Air Conditioner Leaking Water?

Water leak

Ever notice a pool of water under the indoor unit of your central air conditioner and wonder what could be causing it?

Your A/C experts at Needham Oil Complete are here with answers – but first, a little cooling system anatomy.

The indoor unit on your central air conditioner contains the evaporator coil, which cools the warm air blown over it. This causes condensation (water) to form on the coil, just like how water droplets form on a cold glass of water on a hot day. The condensation from the evaporator coil will eventually drip into a drain pan and down a condensate drain line (a white PVC pipe) that leads out of your home (see diagram).

Drain pan diagram

If water is leaking from the indoor unit of the indoor component of your central A/C, it is coming from somewhere in that chain of components – typically due to one of these five reasons:

  1. A clogged condensate drain line – Dust, dirt, sludge or mold can easily gather in the condensate drain line; this is the most common cause of water leaking from your indoor A/C unit. You can use a shop vac to clear the condensate line, but we wouldn’t recommend it: instead, get a cooling system professional to remove the blockage.
  2. A damaged drain pan – In older air conditioners, the drain pan may be damaged or rusted – which means the water will fall right through. Replacing the pan should correct the problem.
  3. A broken condensate pump – A condensate pump moves water from inside to outside your house; if it’s not operating correctly, water will pool. You will need to repair or replace the pump.
  4. A dirty air filter – Here’s yet another reason to change your A/C air filters! A dirty air filter blocks airflow over the evaporator coil; when that happens, the evaporator coil gets too cold and freezes over. When the ice melts, it drips an excess amount of water that the drain pan may not be able to handle.
  5. Low refrigerant – Low refrigerant will also cause the evaporator coil to freeze over, which will again cause an overflow in the drain pan when the ice melts. Telltale signs of low refrigerant are warm air coming from your vents, ice on your condenser unit, or a hissing or bubbling noise at the location of the leak.

    If you have a refrigerant leak, you will definitely need a professional air conditioning repair; you may even need to replace your central air conditioner, depending on the severity of the leak.

Having problems with the central air conditioning or ductless A/C system in your Middlesex or Norfolk County home? We can help. Call the experts at Needham Oil Complete Heating and Cooling today.