If you notice an unusual smell seeping down from your attic or up from your basement in the summer months, you may have a problem with your air conditioner drain pipe. These pipes are used to carry condensation away from the air conditioner evaporator unit. Sometimes the pipes can be clogged by debris, mold or mildew. One way to keep these pipes clean is to treat them with chemicals such as household bleach.
Turn off the power for the air conditioner where you will be cleaning the drain pipe. Turn off the unit itself or, in the case of larger units directly wired into the circuit, cut the power at the circuit breaker.
Locate the end of the air conditioner drain pipe. This is usually outside or underneath one of the house eaves. Clear away any debris from the pipe exit.
Locate the inlet for the drain pipe in the air conditioner drain pan. If the pipe is currently backed up, it may be hidden underneath a layer of water. Feel around the edges of the pan with your fingers until you locate the inlet.
Remove any large clogs in the inlet manually. Slowly feed a length of plastic tubing into the drainpipe until you feel it hit the clog. Move the tube back and forth until the clog loosens and you can push the tubing all the way through the pipe.
Pour fresh water down the drain pipe to rinse it out.
Pour household bleach down the drainpipe to flush the drain and kill any mold or mildew.
Pour fresh water down the drain pipe to flush out the bleach. Do this two or three times, if needed, until you can no longer smell the bleach in the pipe.
Restore the power to the air conditioner unit.