Keeping Your Condensate Line Clean HVAC Training

by Dave on April 10, 2010

So here I am in the sunny state of Florida, and the people are starting to turn on their air conditioning systems again here at the 500 unit apartment complex, and it is time for me myself to go back to some of the HVAC training that I have learned in the past. Being that I am in Florida I do not get much chance to work on heaters, thought this year was a little bit different, as the temperatures here in Florida were a bit colder. But let’s get onto some more hvac training and troubleshooting, particularly keeping that condensate line clear and free of slime sludge and other things that will eventually cause the line to clog up, such as dead lizards and stuff.

So here at the complex our HVAC systems are electric when it comes to the cooling part. It is a split HVAC system, meaning that the air handler, which has the cooling coil inside of it, is located inside of the apartment, and the condensing unit is located on the outside of the apartment. Inside the air handler is a drip pan, where the lines will condensate when the coil is removing the heat from the room, then the condensate drips into the drip pan, then into the pvc piping which leads to the outside, where the condensation will drain.

Now this works quite well but there always seems to be problems with the condensation lines getting clogged up with slime sludge growth, and it tends to build up the most during the ending of the winter month. When the line gets clogged up, the water, or condensation will have nowhere to go anymore, and it will back up into the drip pan and either hit the float switch, thus shutting the air conditioning units down, or the air conditioning will continue to run and flood your apartment, or home. Hopefully you have a float safety switch installed in the air handler, as if it is a newer air handler it is mandatory and up to Florida code that you have one installed on your air conditioning system.

There are a couple of ways that you can clean out condensate lines. One way would be to use a wet/dry vacuum and suck the line out, although this could leave some slime sludge behind, and a couple of months later if not sooner you will have the same problem again. Another way that you can clean out a condensate line is by using a type of air gun, also known as a gallow gun. What it is basically is a gun that you load up with c02 cartridges, you cut the pvc line and insert the gun into the line and blow away. This usually does a fairly good job of cleaning the line out.

Some people will even go as far as pouring bleach or drain cleaner down their condensate line to clean it out, which will also work in some cases. So for the purpose of this hvac training, what is really the best way to clear a condensate line? I use the combination of the gallow gun and at the same time use the wet/dry vacuum outside.

This way I know for a fact that the line is going to be cleaned out. After that I would insert slime tablets into the drip pan, there are lots of brands out there and they will prevent the growth of slime inside of your condensate line, meaning that you should not have as much as a problem getting the line clogged, most require you to use the tablets monthly.

If you have done the above and know that the line is clear, but it is still backing up, you may have to level your air handler. You will also want to make sure that at no point is your drain line rise above the drip pan, if it does it is not going to drain properly unless you have a drain pump that is attached to the condensate line. Hopefully this was enough HVAC training to cure your clogged condensate line problem as it is what I deal with day in and day out and always fix the problem, any questions or concerns drop me a comment and I will get back to you soon!

{ 17 comments… read them below or add one }

Richard Eaton July 5, 2010 at 12:38 pm

Hi,
I really like reading your stuff, very helpful. I am a student right now learning HVAC and this is my last semester. I wanted to ask you a question concerning the coils on the inside of the house. They have never been cleaned and they are pretty nasty looking. I have a 10 yr old split-system heat pump. I went on you tube and looked at a video where the tech took the whole unit out and cleaned it with coil cleaner. Is there a simpler way of cleaning the coils instead of taking it outside? Thanks…Richard

Dave July 20, 2010 at 12:17 am

It really all depends on what type of air handler you have and where it is located. The absolute best and most effective way of cleaning coils is unfortunitly to pull them out and spray them down with a hose along with some coil cleaner.

Bob August 5, 2010 at 7:54 pm

Dave, The condensate line in my house has clogged twice in two years and each time, my wife had to deal with the issue by calling an HVAC repairman. We’re snowbirds and so we’re not around enough from May thru October to regularly clean the line. I like the idea of the tablets, but it doesn’t look like it will work for us because they have to be replaced monthly. Would replacing the current line with a larger diameter pvc pipe help the situation?

missy August 6, 2010 at 4:58 pm

I’m not really sure, but my condo has had problems for 4 or 5 years backing up and not draining outside. This year the AC guy says the problem is that a filter on the AC is clogged with drywall particals. This is possible, but doesn’t seem to be the root of my problems because I install the new drywall after the unit flooded and mold was on the walls. Last year the AC guy says the problem is that the floater switch broke. I’ve been cleaning the line with my dry vac. I do pour bleach in the summer. My unit has floaded three times… and I keep watching it and the drainpan continues to fill. The unit is usually pretty confortable… sometimes too cold and other times I’m confortable… but i dont touch the temp. My friend suggested using c02 cartridges pressure to clear the line and maybe the line is never clearing out. My friend knows an AC guy and he told the situation too. I wanted your oppinion. I chance the filter every two months (says to change ever 3 months) but he says their is another filter that you have to take ac part to get to and thats the dirty one. They will do it for 1,000 dollars and it takes about 5 or 6 hours. He says he’s giving a discount because no one cought it in 4 or 5 yr and the other tec who came to clean it didn’t say anything.

Dave August 12, 2010 at 1:22 am

Bob, call a local HVAC company and set up a maintenance, most companies will come out twice a year and clean your drain line, along with checking the overall efficiency of your complete HVAC system. That will run you 150 bucks and up a year, much cheaper than a service call to get someone out to clean it for you. About the PVC, it MAY help, but I also do not know how your system is set up and may be more expensive over all to do that, regular maintenance should keep it clean, shop vacuums taking suction on a drain line while hot water is being poured in the drain pan does wonders. Hint Hint.

Missy I have never heard of that before. They do not design them to make the filter access hard to get to. If you have dirty air handler coils, that can only be accessed by taking the air handler apart to clean them, that is a different story, but I can almost assure you there is no filter inside the unit that makes it so hard to get to that you have to charge 500 dollars, aside from some rare commercial type units.

Nick September 13, 2010 at 8:54 am

Hi,

First, I’d like to say that I find this information very useful, but unfortunately, I’m still having problems. I recently started noticing water dripping, well more like running, from a pipe I’ve never seen it drip from before. So I started doing some research and learned that it was the back up drain line for my Air Conditioner condensate. I read different methods of clearing the line. First, I tried to access the clean out on the primary drain pipe to pour some bleach down it. Unfortunately for me, who ever installed the AC in my house didn’t put a clean out on it. So I tried another method, the shopvac. This was ineffective. So, my brother is a plumber and I thought I’d have him look at it and maybe put a cleanout on it for me so I could pour some bleach down the drain. When he cut the pipe to do so, we realized the drain pipe wasn’t even clogged. It seems to be clogged before the condensate p-trap. Like maybe in the unit itself. I’ve tried to see what I can do to fix this and I’m not finding anything online. Is there anything I can try to do before I pay someone for a service call?? Thank you for your time!

Jonathan Martinez April 9, 2011 at 8:17 am

I have one question to ask, ” What is the purpose of a P-trap on the condenser drain line?

Dave April 20, 2011 at 1:15 am

Jonathan, that is a tough question to answer, if the evap coil is on the negative side, they are needed as air bubbles could occur if not and mess up the way the line is draining, if the evap coil is on the positive side, the trap helps keep the air from escaping the unit.

Many AC techs may have different answers, but they are almost always needed….why? Because the installation manual for every system I’ve seen says they do ;)

Lisa Young August 10, 2011 at 3:28 pm

I have a manufactured home, half the vents in house was working and the other half wasn’t. we went under the house and the duct connecting the main unit to the run on the half not working, was full of water. (5 gallons if i could guess) we replaced the line and it is working fine now. my concern is the condensation will fill it up again. Also, it is warping my door and flooring by the unit inside my laundry room. its wet. Help! I had HVAC guys come out and they filled the r-22 in unit. said condensation was normal. 5 gallons?? why is it in the duct? plastic pipe is underneath to drain water. Worried

Dan August 14, 2011 at 6:16 am

I don’t know if it is just me but this year I seem to be really having a problem with the slime mold in the a/c condensation drain line. Even the family car a/c drain has backed up and flooded the passenger side. Years ago I cut the PVC line and added a twist together joint as to allow access with the garden hose. About once a year I would have to blast it out from the garage. Outside it always looked like an elephant snoted along side the house. This summer I have done it twice. Now I added another PVC fitting to allow for bleach to be added. I’m wondering if it will help or just flush through. I may have to do it monthly, along with the regular filter change. It’s been really hot and humid this year in Florida. I was wondering your thoughts. –Dan

DAN August 21, 2011 at 8:59 pm

Is it possible that a neglected air filter could become so dirty that the air handler begins to leak from the condensate line?

Carmen August 29, 2011 at 2:36 am

We’ve had the upstairs line back up on us four times this year – and it’s in the attic, so our upstairs ceiling looks horrific. I found this page with a Google search and wondered if you have any thoughts on why the line might keep backing up. We’ve thoroughly flushed it each time and yet, about 3 weeks later – the ceiling starts to drip and it’s clogged.

Mark September 26, 2011 at 2:02 am

Hello,

My condensate line has been clogging regularly. I did the bleach and gallo gun, but it seems to have clogged again. The line drains into a crawl space that is difficult to access. Are there any stronger liquids than drain-o that I could use?

Dave October 19, 2011 at 11:07 pm

Carmen and Lisa – your line could be clean, you may have a cracked drain pan….which would have to be replaced.

Dan make sure that your pvc clean out is capped. If you have a P-trap you can add a vent AFTER it and make sure the vent pipe is ABOVE the the drain pan….usually helps with condensation flow.

Johnny February 26, 2012 at 9:37 pm

I have been having a condensate problem, but I have been able to pour clean water down the clean out and it comes out the other end. I took the line from the handler and it was clean as well. My issue is that I am still having condensate fill up the reservoir for the SafeT switch.

Dave March 7, 2013 at 4:36 am

Richard,
I work at a place that looks after split sytems In accommodation blocks
We remove the covers and a have a canvas type of bag
That straps around with a drain hose on the bag
we can then spray the coils and wash the drains
without having to pump the unit down and removing it

Mohamed July 11, 2013 at 4:13 am

Hello Dave,
Thanks for the great information I plan to tackle cleaning, blowing and sucking my condensate line at my condo. My condo is a second floor unit in a multi unit building 8 to be exact. Im understanding the blowing from upstairs and sucking from outside. I can cut the pvc to get my air compressor and attachments around the hole from inside the condo upstairs to blow air down, however from outside the building im having trouble finding where to suck from? On multi family buildings like apartment style complexs. Would it be running to my exterior unit? I thought at my parents house there was a white pvc outlet abouy 3/4 inch to attach our shop vac too but am confused with my condo. Please advise and thanks again

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