How Often Should You Put Bleach Down an Air Conditioner Drain Pipe?

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Bleach does whiten an air conditioner by killing dark algae and mold in the system.
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Bleach more often is poured into a clothes washer, but it also has anti-microbial properties that make it useful for air conditioning systems. Because air conditioners produce water through condensation as you operate them, they are prone to mold and algae. Bleach is used to clear blockages caused by these and prevent future growth of these organisms, but only if you use the bleach in the correct manner. Properly timing metered doses of bleach to your air conditioning system should prevent microbial growth in the system without becoming a burdensome chore.


Why Use Bleach

Bleach will kill the mold and algae that grow in the air conditioner's condenser pan. These thrive in the moist environment produced by the air conditioner's condensation. The water in the pan is stagnant and slightly warmed by the air conditioner's motor. These produce ideal conditions for the growth of mold and algae. Over time, these build up in the condenser pan and drain pipe, causing blockages and possibly getting mold spores into the air circulating throughout the home. Bleach helps to kill these organisms and prevent them from growing in the future, keeping you and your family healthy.


How to Use Bleach in Air Conditioners

Before putting bleach in an air conditioner you must dilute it. This will reduce the potency of the bleach so that it does not damage the interior of the drain pipe. Mix 2 tablespoons bleach with 1/2 cup hot water and pour it down the drain pipe leading from the evaporator coil to the condenser pan. Leave the diluted bleach in the condenser pan to continue to kill algae and bacteria throughout the season.

Frequency of Bleach Use

Bleaching should not be done too often because excessive use can be corrosive to the pipes. Check your air conditioner before you start it up for the warm-weather season and after the season ends. Add the diluted bleach solution to the drain pipe at each check of the system. Repeat the process if you notice water dripping from under you air conditioner. This indicates that the drain pipe has clogged and is overflowing into the condenser pan.



Bleach must be diluted before putting into the drain pipe. Bleach tablets, though designed for air conditioner use, should not be used, warns Mark Mehling in "Leaving Your Home Alone: A Do-It-Yourself Step by Step Guide to Leaving Your Investment Empty for Months at a Time." Only use diluted bleach and never mix it with ammonia-containing products. Wear gloves to protect your hands while handling the bleach. Turn off your air conditioning system before disconnecting the drain pipe to add the bleach.


Athena Hessong

Athena Hessong began her freelance writing career in 2004. She draws upon experiences and knowledge gained from teaching all high-school subjects for seven years. Hessong earned a Bachelor in Arts in history from the University of Houston.