Why a Room Air Conditioner Blows in Condensed Water

A man sets up a room AC unit.

Your room air conditioner, as well as cooling the air, also has the desirable side effect of removing humidity from the air. But sometimes, a room air conditioner will blow condensed water back into the room. When this happens, it can mean your air conditioner's primary drain is blocked, and condensed water cannot escape. Here are tips to determine whether your room air conditioner is blowing in evaporated water, and how to correct this problem.

Normal Air Conditioner Function

When its air vent is closed, a room air conditioner will draw in the room's warm air with its fan, condense the water from that warm, moist air, send the air over the condenser to cool it, and return cool air to the room. In the bottom of the air conditioner unit, in the portion that is outside the window, is a drain that lets the condensed water escape to the outdoors. Since it is a fine mist when it leaves the air conditioner, it does not drip and create moisture problems around the air conditioner case or on the exterior walls of your home.

Air Conditioner Function with a Blocked Primary Drain

Sometimes, due to pulling in air contaminated with dust and fine hair, the filter and then the primary drain can become blocked. The drain cannot allow the water to escape when it is a fine evaporated mist. Instead, the water cools slightly, returning to its liquid state. Because it is harmful for this liquid water to pool inside the air conditioner, a secondary drip drain will allow it to be flushed out of the air conditioner housing. This function explains why you often see air conditioners "dripping" in hot weather. Some of this liquid water will be swirled around by the fan and blown back into the room. It will dampen your drapes, carpet, walls and anything else in the path of the air conditioner faceplate. This can lead to mold and mildew buildup on fabrics in the room and in the air, a highly undesirable situation.

Correcting the Evaporated Water Drain Blockage

Turn off the air conditioner, unplug it from the outlet, remove the faceplate, and clean the filter. Clean as much of the interior side of the air conditioning unit as you can. Wipe up damp places, and remove ingrained dust trapped in corners of the faceplate and the housing. You will need to contact an air conditioner technician to open up the exterior compartment of the air conditioner, to clean the compressor and condenser and clear blockage from the primary water drain. Do not attempt to make these repairs yourself as you could sustain electrical shock injury, and void the warranty on your air conditioner.

Preventing Drain Blockage

Have a qualified technician inspect your air conditioner annually, either at the end of the season or before you set up and use it in summer. Vacuum and dust the room where the air conditioner is installed more often than other rooms. Do not treat the air conditioner as an air purifier.