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A/C Condensate Drain Pipe Unclogging & Cleaning Guide
Pictures illustrated instructions for how to unclog, clean & flush out an HVAC Air Handler unit's condensation water drain pipe.

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Please note, I am not a professional HVAC service person. This guide is for illustrative purposes only. If you have any doubts, do not proceed and contact an air conditioning repair company. Continue at your own risk.
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Home A/C Air Handler
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Rheem Drain Pipes
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Clogged Drain Sensor

I learned from a past experience that it's important to regularly clean and maintain a home A/C air handler unit's condensate drain pipe.

Our former home had the HVAC air handler installed above the ceiling in the attic.

The condensation drain pipe that allows water to flow from the air handler's drip pan to the outside of the home had become clogged with fungus, mildew, algae, debris and even small plants.

Once the pipe was clogged, the air handler's evaporator drip pan overflowed and water began leaking down through a bathroom exhaust fan.

A yearly cleaning regiment could have prevented the clog and the subsequent water damage to the ceiling.

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Condensation Drain Pipe
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Drain Pipe Access Cover
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Remove Drain Pipe Cap
The first step is to turn off the air conditioner at the thermostat and then at the circuit breaker located in the circuit breaker box or on the front of the air handler unit itself.
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Mold, Fungus, Slime
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Turn Off Air Conditioner
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Rigid Wet/Dry Vacuum
Then locate the condensate drain pipe access cover cap right located on the PVC plastic pipe coming out of the front of the air handler unit. If there is no access cap, you may need to unscrew part of the PVC pipe in order to be able to flush out the line.

If you'd like to skip the pipe flushing step, you could just find where the drain pipe terminates outside your home and suck out any fungus or debris with a powerful wet/dry shop vacuum.

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Suck Out Blockage
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Create Seal Around Opening
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Remove Overflow Sensor
After removing the drain pipe access cover, I placed the wet/dry vacuum's hose on the opening and created a better seal using my hands. I let the vacuum run for about 30 seconds, turned it off, and checked the results inside the vacuum's container. There was a small amount of water and a few small bits of fungus inside the container. If your condensate drain was clogged, you should see substantially more water and algae, fungus, mold or slime inside the container.

You can also try moving the wet/dry vacuum's hose to the "blow" side of the machine and send some air through the pipe to force any remaining obstructions to the outside of the home. If you still feel that the pipe may be clogged, find the exit point of the pipe outside the home and vacuum it with the wet/dry shop vacuum.

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Drip Pan Overflow Sensor
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To be thorough, I also pulled out the drip pan's overflow sensor and vacuumed out that pipe as well. If you're lucky enough to have an air handler equipped with an overflow sensor, you won't have to worry much about water leaks. When the condensate pipe becomes clogged, the drip pan fills up and the sensor turns off the air conditioning system.


 
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Vacuum Out Pipe
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1/4 Full Bleach Bottle
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Large Funnel Inserted
In order to keep the condensate drain pipe clean in the future and prevent mold/mildew/algae/fungus from growing, I poured 1/4 of a bottle of full strength bleach down the condensate drain pipe's access hole using a large automotive funnel. I waited for about 30 minutes to allow the bleach to kill any microbes living inside the pipe and then flushed it out. To flush out the line, I refilled the empty 1 gallon bleach container with water and poured it down the drain pipe access hole several times.
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Pouring In Bleach
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Refilling With Water
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Flushing With Diluted Bleach
I also slowly poured a gallon of water into the overflow sensor's housing to flush out the drain pan and further flush the condensate pipe at the same time. I didn't want to leave any bleach sitting in the drain pan or the the PVC pipes since I've read that bleach may cause damage to any metal pieces, the glue that holds the PVC pipes together, and the PVC pipes themselves.
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Flush A/C Drain Pipe
Once I was done flushing out the air handler condensate pipe and the evaporator drip pan, I removed the funnel and replaced the access hole cap and the overflow sensor. Just in case, I checked all around the HVAC air handler unit and and the drain pipes looking for any water leaks.
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Air Handler Fuse Box
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Turn A/C Back On
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Replace Drain Pipe Cap
Now that everything was back in place, I switched the air handler's circuit breaker and the A/C thermostat back on. My last step was to mark the calendar to repeat this procedure next year. If you live in an especially hot and humid environment, you may want to check, clean, and flush out the condensate drain pipe at least twice a year.
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Replace Clogged Drain Sensor
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For more of my related home maintenance guides, click on the following links: A/C Run/Start Capacitor Replacement Guide, Dryer Hot Air Exhaust Vent Cleaning Guide, HVAC Air Handler Evaporator Coils Cleaning Guide, Culligan US-600A Undersink Water Filter Installation Guide, Culligan Refrigerator Icemaker Installation Guide, Kitchen Sink Drain Leak Repair Guide, Culligan IC-EZ-1 Water Filter Install Guide, Honda EU3000is Generator Maintenance Guide, Sticky Door Lock Lubrication Guide, Hunter Just Right Digital Thermostat Installation Guide, Kenmore Refrigerator Clogged Defrost Drain Pipe Water Leak Repair Guide, N:Vision CFL Light Bulbs, Fagor Pressure Cooker Review, Toilet Water Supply Valve Leak Repair Guide, Kenmore Range 220V Power Supply Repair, Carpenter Bee Pest Control Guide, and How To Deep Fry A Turkey.
 
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