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Gibson A/C Air Handler Condensate Drain Pipe Flushing Guide
How to unclog, flush out, and clean the condensation water drainage line of a Gibson HVAC air handler with pictures.

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Gibson GB3BV-036K-B
Turn Off Thermostat
Turn Off Power Breakers
This home maintenance guide was specifically written to assist owners of the Gibson HVAC Air Handler model # GB3BV-036K-B in unclogging, flushing out, and cleaning the condensate water drain pipe.

Owners of other similar A/C air handlers from manufacturers such as Goodman, Rheem, Trane, GE, Mars, Carrier, York, Lennox, Frigidaire, Kenmore, Mitsubishi, Maytag, and Whirlpool may also find this guide to be helpful.

One of the most immediately obvious symptoms of an A/C system with a clogged up condensate drain pipe is water leaking out from the bottom of the air handler.

If you're lucky, the air handler is equipped with a drip pan overflow shut off switch which will prevent a water leak by turning off the air handler when the drain pipe is backed up.

Gibson Electrical Data
Air Handler PVC Piping
Drain Pipe End Cap
For a condensate drain pipe that is definitely clogged with mildew, mold, or debris, the first step is to suck out the blockage with a wet/dry shop vacuum.

Locate the termination pipe of your air handler's condensate drain pipe outside your home, usually located by the condenser (outside A/C unit), and use the wet/dry shop vacuum to pull out any mold, mildew or debris plugs or obstructions that may have slowly formed over the years.

Cap Removed
Safe-T-Switch Model SS1
Lift Out Shut Off Switch
Even if your condensate drain pipe hasn't become clogged or your Gibson air handler hasn't started leaking water, the pipe should still be flushed out every 6 months to a year depending on your local climate.

First shut off the A/C system at the thermostat, turn off the air handler's power breakers in the A/C closet and also at the home's main breaker box for extra safety.

Open the closet door that hides the HVAC system's air handler unit and locate the PVC pipes running along and below the bottom end of the air handler.

There should be a circular PVC cap covering a short pipe leading into the main drain piper.


Shutoff Switch Removed
Publix Lavender Bleach
Pour Bleach In Pipe End
Remove the pipe cap and pour a small amount of bleach or white vinegar into the pipe.

Then move over to the safety switch if your air handler is equipped with one.

Lift the Safe-T-Switch out of the pipe and pour a small amount of bleach into that hole as well.

Allow the bleach 15 to 30 minutes to kill any bacteria, mold, mildew, or fungus that may be living inside the condensate drain pipe.

Some HVAC professionals warn that using bleach may cause damage to the plastic PVC pipes, but many others agree that this is unlikely since only a small amount of bleach is needed and it is flushed out of the system shortly after ward.

If your A/C system is very old or if you are concerned about damaging it, just stick to vacuuming out the line and flushing it with clean hot water instead of using any sort of chemical biocide.

One advantage to using bleach or white vinegar is that they inhibit the growth of mold/fungus/mildew and allow you to go longer in between condensate drain pipe flushing sessions.

There are also HVAC system cleaners that are specifically made to not damage your A/C system.

Pour Bleach In Switch Pipe
Hot Water In Pitcher
Flush Pipe Hot Water
Once 15-30 minutes has passed since you poured the bleach into the drain pipe and shutoff switch hole, you can pour in a pitcher of hot water to flush away the bleach.

Be careful when you pour water into the Safe-T-Switch's hole since the water may rise up through the primary access hole.

Vacuum Out Blockage
Flush Out Drip Pan & Switch
Replace Drain Pipe Cap
It's a good idea to go outside after you pour some hot water into the condensate drain pipe to see if the water is flowing well out of the end of the pipe.

If the water is flowing out quickly, go inside and pour several more pitchers of hot water through the line and shutoff switch pipe to thoroughly remove the bleach from the air handler's drip pan and condensation drain pipe.

Clean & Replace Shutoff Switch
Turn On Power Breakers
Turn On Thermostat
To finish the job, drop the shutoff switch back into the hole and replace the condensate drain pipe's end cap.

Turn on the power breakers at the air handler and in the home's main breaker box.

Finally, turn on the A/C system at the thermostat.

If the system doesn't turn on, double check that the safety switch is in the correct "down" position inside the pipe, check that all the breaker switches are turned back on and turn down the temperature setting on the thermostat.

For more of my home repair and maintenance guides, please click on the following links: Rheem A/C Capacitor Replacement Guide, Rheem HVAC Condenser Coils Cleaning Guide, Refrigerator Freezer Icemaker Replacement Guide, Bathtub Shower Diverter Valve Replacement Guide, Home Water Heater Sediment Flushing Guide, Rheem HVAC Air Handle Coils Cleaning Guide, A/C Condensate Water Drain Pipe Flushing Guide, Home Clothes Dryer Lint Vent Cleaning Guide, Laptop HDMI To HDTV Over CAT6 Connection Guide, Culligan US-600A Under Sink Water Filter Installation Guide, Culligan IC-EZ-1 Drinking Water Filter Installation Guide, Culligan IC-100 Icemaker Water Filter Installation Guide, Kitchen Sink Drain Leak Repair Guide, Hunter Just Right Digital Thermostat Installation Guide, Sticky Door Lock Lubrication Guide, Honda EU3000is Generator Maintenance Guide, Kenmore Oven/Range 220V Power Restoration Guide, Toilet Water Supply Valve Leak Repair Guide, Refrigerator Water Leak Repair Guide, GE HVAC Condenser Dual Run Capacitor Replacement Guide, Delta 75520 Massaging Shower Head Installation Guide, and the Carpenter Bee Insect Pest Control Guide.

Check out all of my Home DIY Repair & Maintenance Guides.

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