Why Does My AC Drain Keep Clogging? Learn How To Unclog it.


Over time, dust gets past your air filter and into your ac coil. As condensation drips down your ac coil into the condensation drain pan some of those same impurities flow down the condensate drain and into the trap where they set and turn to a drain plugging sludge. Some of this same sludge collects right at drain connection to the pan.

Not enough slope or additional traps created by piping being incorrectly installed will cause other areas to plug and backup your drain.

Wherever moisture is collecting, which is mostly in the drain pan, the place where mold and algae is creating the sludge that has been plugging your drain.

Removing the sludge in the drain will probably get you by for the season but you’ve got to fix the problem to stop all that debris from coming down the duct into the coil to go down the drain and plugging it again.

Looking up the air stream toward the filter will give you some indication of where that dust is coming from.

A thorough duct and coil cleaning and filter upgrade will keep that condensate drain clean for much longer.

Cleaning the coil with a vacuum rarely works as the debris is usually quite stuck to the coil. Sometimes a semi stiff brush can help. This stuff on the coil is also deeply embedded into the coil not just on the surface.

Chemicals are the best way to get the job done. There are some wonderful products that can be easily sprayed on the coil and also aid in cleaning the drain lines.

Amazon has these if that’s your preference for shopping. Take a look there and get some ideas for what will work.

This foam cleaner is self rinsing and has a lemon order.

Why the dust is getting to the coil needs to be addressed.

To keep future dust from getting past your filter and plugging your drain make sure your filter is the proper type and size.

Also that it fits snugly on all four sides not letting any air short circuit past it.

Where Is My AC Drain Line And Coil Pan

Hopefully you can find easy access to the condensation drain pan and remove the algae and moldy stuff that has piled up against the origin of the drain line.

If you’re having a problem locating the drain, look for the white 3/4 inch PVC pipe attached to your furnace.

The coil will very likely be right behind the panels directly above the drain.

How To Unclog An AC Drain Pipe

Here’s a few tips on how to clean an air conditioner condensation drain line

Sometimes a wet dry vac with a skinny tip on the hose will allow you to suck up a lot of what’s plugging the drain.

Having done that and your drain is still plugged you can find several drain cleaning tools available online.

From suckers to blowers or even brushes to shove down the pipe.

You may even like the idea of an ac drain line cleaner or ac drain line tablets

If none of these are down your alley or you’ve already tried some to no avail and you continue to have a constant issue with your ac drain plugging, it’s time to start over.

Vinegar vs Bleach For Cleaning An AC Drain

You can choose. But bleach stinks, it’s vapors can be harmful and it never fails to get on something it shouldn’t.

A half portion of bleach and water down the drain in the cooling season would probably do no harm.

Leaving the bleach in the drain trap in the heating season when it won’t get flushed out by a running ac could be a might caustic for the pipe.

Bleach will attack the PVC and the glue in the joints allowing the line to leak or fall apart.

Vinegar does the same job without any harmful results. For the best cleaning use regular distilled white vinegar.

Can You Snake An AC Drain Line?

Even if you do find or already have a snake just the right size and flexibility to run down a 3/4 PVC pipe wouldn’t it be easier and more effective to get a half dozen 3/4 couplings, some PVC glue and cut the drain line.

Take it outside and hose it out. Bring it back in and maybe snake some parts of the line that you didn’t want to remove and then reassemble the pipe.

Always double check the slope.

Install A New AC Drain Line

Just cut the old one off and install some new clean PVC. This time do it right and provide a clean-out just above your trap so you can easily treat and/or flush that trap on a yearly basis.

If you can’t find a preformed trap then shape one out of a few slip by slip 90’s or some street ells.

Traps are an essential part of a condensate drain. Without a trap you can actually block the flow of condensation from leaving the pan.

When the indoor fan or blower runs

Negative air pressure created around the area of the evaporator coil will pull air up through the drain pipe into the pan and the pan will fill with water and overflow.

Not all systems will do that, but if you had no trap and condensation is leaking around your coil and furnace area that could be the problem.

Make sure you use the proper ac drain pipe size. 3/4 inch PVC pipe and fittings. Reducing the size is asking for the same problem to occur later on.

Proper PVC Gluing. Do I Need A Primer?

The industry highly recommends using a PVC primer. It so happens that PVC is not glued together, it is actually fused together.

The process of fusing begins with the primer. It’s purpose is to soften the PVC and the glue finishes the job to make the proper seal.

You’ll have to decide if that’s how you want to assemble your PVC. Remember it’s not under pressure. The likelihood of it leaking is slim if your joints are clean and tightly pushed together.

If your PVC job is over a finished room, use a primer.

Why Is My AC Drain Pipe Making Noise

It goes back to having no trap or a trap that is empty. Negative air pressure in the return side of a furnace will pull air from the exit point of the drain line.

With just a small amount of condensation in the drain pan it will gurgle like crazy against the drain until enough condensate is created in the pan.

When the fan shuts off the condensate will flow down the drain and fill the trap. Hopefully.

Why Does My Air Conditioner Have Condensation?

Condensation is the moisture in the air related to humidity. Some areas of the country such as the deep southeastern United States have more humidity than some northwestern high desert areas.

Air conditioning systems in sections of the world that have high humidity can produce several gallons of condensation per day while high desert or dryer climates can be less that a gallon.

So if you were to ask how much condensation from a home ac is normal the answer would be “it depends on where you live”

What If My Home AC Has No Condensation?

If you live in an area that has relatively no humidity or a season of the year where humidity is near nothing then it may be hard to tell without a service call from your favorite tech.

On the other hand if humidity is high and no water is coming out of your ac drain, then likelihood is your ac is low on charge.

Many other factors enter into this scenario when your air conditioner is not draining water. Coils ice up and airflow would be very low if any at all.

Chad Peterson

Chad Peterson is near 40 year veteran of the HVAC industry. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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