Question about HVAC drain line clog


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Old 04-29-23, 08:29 PM
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Question about HVAC drain line clog

Hello,

I have a question regarding my new Lennox heat pump that was installed almost exactly 2 years ago. Over the last few days while the AC was running, I noticed a fair amount of water pooling in the drain pain for some reason. My immediate thought was whether the water was actually draining through the drain line. When I pulled off the drain cap (see label #1), water immediately started overflowing at this point. Next, I decided to cut the drain pipe (see label #2) and once it was cut through, no water drained out which told me the clog was in that section. Luckily, the clog was right at this P-trap and not further down the line where there was no access (in my condo). You can see the 'gunk' that I cleaned out of the P-trap!

My question is whether this drain line should ever get clogged? When I pulled off the drain assembly from the indoor unit, I gently inserted a long screw driver through the drain hole and I could feel the screw driver on the other side - I did this because I wasn't sure if there is supposed to be any kind of filter covering the drain hole to prevent gunk from getting into the drain line.

I guess my question is, is it normal for gunk to get in the drain line on occasion? Is there any way to prevent this from happening in the future?

Thanks in advance!





 
  #2  
Old 04-29-23, 08:36 PM
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They do get slimed up. You just need to do some preventative maintenance. Once or twice a year, dump a little cleaner down it and blow it out with an air gun. Keeping your filters clean and a-coils clean will help too. Also a maintenence item.
 
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Old 04-30-23, 04:28 AM
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Crud just forms.

Two things I did when the original drain line on my GEO clogged, went to a larger line and eliminated the trap. Now the condensate just flows straight down into the floor drain.
 
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Old 04-30-23, 12:51 PM
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XSleeper - thank you for this. I will keep an eye on this in the future.

Marq1 - thanks for this. That makes sense... it thought it was strange that I have owned a number of homes over the years and have never had a clogged drain line before. The larger line with no trap makes sense.
 
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Old 04-30-23, 02:17 PM
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3/4" drain line is fine for an air handler.
However.... if it's not installed right it will cause problems.
In the picture I labeled A and B. One is slightly lower than the the other.
The lower one is the (primary) drain and the upper one is the (secondary) overflow.

It sounds like they are backwards. If they were correct.... the float switch should shut the condenser down before any overflow from the internal pan.

If the lines are in the correct location.... the clog is 99% of the time inside the air handler at the 3/4" connection. That overflow switch should not be glued in place. You should be able to pick it up and pour a mixture of hot warm and bleach down and it will eat the algae and gunk and open the drain fitting.


 
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Old 04-30-23, 03:16 PM
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PJmax - thanks so much for this info! It is hard for me to tell which is lower - whether it is 'A' or 'B'. Yes, the shutoff switch is certainly siliconed into place.

Regarding the system 'shutting' off when water is detected, I wondered why that did not happen. There was a fair amount of water in the low spot of the drain pan, but a very small amount of water did touch item '3' in the picture that I just attached. I thought this was also some kind of shut off switch as well?

 
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Old 04-30-23, 03:39 PM
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The safety switch should not be siliconed in place.
It should be pulled out and the silicone cleaned up and removed.
There's a good chance the " installer " got silicone on the float..... causing it to bind.

You have the side of the air handler off.
You could pour a half gallon of hot water with two cups of bleach in near the drain fittings.
 
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Old 06-29-23, 06:42 PM
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Here is what i do to maintain a clean and clear condensate drain line from the HVAC A-Coil to beneath the bathroom lavatory sink.

Once every 2 months (at maximum) I pour about two cups (16 oz) of hydrogen peroxide into the open " PVC riser standpipe vent for the primary condensation line using a funnel. It takes me all of maybe 3-4 minutes! I always turn Off the HVAC at the thermostat (not at the service switch) beforehand so the blower doesn't run for a few minutes so it can start dissolving any clog/blockage that might be getting started in the condensate drain pipe. Hydrogen Peroxide is usually available in 16 oz and 32 oz bottles and is very inexpensive at only $1 a bottle. It does a great job of dissolving algae and gunk. I refrain from using bleach because it is said to possibly damage PVC cement at joints plus if you spill it on your clothes it will bleach the fabric! White 3% vinegar is okay to use as well.

This disinfecting/cleansing procedure should be done once every 2 months (at maximum) during the months with heavy A/C use. During cooler months when heating is needed I'll do it every 3 months. Again, iIt takes me all of maybe 3-4 minutes

My " PVC standpipe acts as at vent to the atmosphere and must remain open and should not be capped.

My HVAC condensation line does not have a P-trap. A P-trap is not needed in a system when the A-Coil and its condensate line is on the positive side. In this setup the condensate line only needs to have an open vent to the atmosphere/attic. If however a P-trap is installed for code purposes it must be vented on the coil side. It is important that this vent pipe not be capped because condensate water will not drain properly. Pressurized blower air from the A-Coil cabinet, along with the open standpipe vent helps push the condensate water out of the condensate line, which typically drains underneath a bathroom lavatory sink, below its drain and but above its P-trap. If the standpipe vent is capped then it creates a condition where the vent air can't help push the condensate water out - - and the sink where the condensate is to drain out can't drain very well because blower's air pressure would block water from draining out of the sink's bowl at the small gap of the drain stopper is located in the lavatory sink. The " PVC vent pipe for the primary condensate line is to be left open to the atmosphere/attic. FYI, the small amount of cool air released into the attic from the " diameter PVC open vent pipe is insignificant and trivial.
 

Last edited by Kooter; 06-29-23 at 07:04 PM. Reason: orthography
 

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