Author Topic: Clearing blocked AC roof drain  (Read 1241 times)

Mike Shumack

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Clearing blocked AC roof drain
« on: September 26, 2021, 06:03:17 PM »
Do you have to remove the AC unit to clean out a blocked AC condensate drain? I have a Dometic Duo-Therm AC/heatpump unit.
Can I try blowing air up from the bottom (assuming I can find the outlet end of the drain hose) or is that likely to blow the hose off the drain pan nipple (or worse)?

I see the small condensate pan under the AC unit (it looks to be overflowing onto the roof) but I don't see a way to access it.
Also is that drain pan provided by Dometic? It is not shown in my parts manual, and the installation manual doesn't show it either.

Since my initial post, I found this YouTube video on the subject, and it doesn't look like you can do much without removing the AC from the roof. That's a lot of work. So I should order a new drain pan and a mounting gasket before going any further - if I'm understanding this correctly.
https://www.youtube.com/watch?v=2scGzlZI1gI
« Last Edit: September 26, 2021, 06:14:14 PM by Mike Shumack »

Bill Lampkin

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Re: Clearing blocked AC roof drain
« Reply #1 on: September 26, 2021, 06:26:03 PM »
Mike, I suspected my roof A/C drains were not working so I found the drain lines (big 1/2 id black rubber hose) front ac drains just behind front drivers slide, rear a/c drains right on top of my tailpipe extension (curb side rear). I took a smaller dia hose and blew into the front ac drain and it took a bit of pressure but hose was clear. I found that they will drain when the coach is level, especially side to side. I think the drip pans drop into the base frame of the ac unit, so you would have to pull off the cover. The pans connect to each other with clear pvc tubing. You can do a search for drip pan kit (I think) and find the parts. But I suspect any issue has more to do with being slightly out of level.
2005 Patriot Thunder Lexington, 3 slides
40' tag axle (short wheelbase)
525 hp C13

"Goin where the weather suits my clothes..."

Bill Lampkin

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Re: Clearing blocked AC roof drain
« Reply #2 on: September 26, 2021, 07:38:02 PM »
I think you need two gaskets per A/C unit if you want to order new drain pan kit. Not sure if kit comes with one or two gaskets.
2005 Patriot Thunder Lexington, 3 slides
40' tag axle (short wheelbase)
525 hp C13

"Goin where the weather suits my clothes..."

Fred Brooks

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Re: Clearing blocked AC roof drain
« Reply #3 on: September 26, 2021, 08:02:25 PM »
   Mike,
You can access the drain hose from inside the coach. I am not sure if you have a decorative ceiling panel that hinges downward. It would be the same process of access to clean the filter. You may need to remove the ceiling clamp ring that has bolts at each corner. You will see the drain hose and wye that connects both sides to the drain hose. Disconnect and blow compressed air in both directions. Run the air to confirm the repair. Fred
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2000 Marquis, Jasper
C-12 Wild Cat (U of A)
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Proverbs 3: 5 & 6

Mike Shumack

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Re: Clearing blocked AC roof drain
« Reply #4 on: September 27, 2021, 11:45:25 AM »
Thanks for your help again.

The video I found (linked to in my first post) shows how the hoses are connected - as you said they can be accessed from the inside by dropping the ceiling trim panel. This would be the preferred way I think. However, on my '05 I know the front ceiling trim is not hinged. It's heavy. I had that one down to replace the ambient lighting rope lighting (I rented a drywall lift to lower the panel). I have not had the rear celling panel down but I assume it is the same and not hinged. Its a smaller panel so not as heavy but would take two people to lower it -

I was concerned that blowing air up form the bottom might blow the hose off the connectors/nipples, but it sounds like that should not be a problem since you did it that way. So that will be my first attempt. I'm guessing there is just some algae or similar gunk stopping up the hose. Now I 'll see if I can find the end of the hose somewhere near the exhaust tip.

Fred Brooks

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Re: Clearing blocked AC roof drain
« Reply #5 on: September 27, 2021, 03:07:53 PM »
   I think the front drain hose runs down the "A" pillar on the drivers side and the rear drain hose where you said. You are experiencing normal accumulation of debris and algae seeing you reside in Florida. Sort little blasts of air will dislodge the muck. Good luck and find some help dropping the ceiling panel. Blessings, Fred
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6

Bill Lampkin

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Re: Clearing blocked AC roof drain
« Reply #6 on: September 27, 2021, 03:23:00 PM »
I used a low-pressure compressor (my lungs) to see if the drain hose was clear. On my coach, the rubber hose for the front AC unit runs thru the pass thru compartment, which is forward of the wet bay and adjacent to the drivers side slide.
2005 Patriot Thunder Lexington, 3 slides
40' tag axle (short wheelbase)
525 hp C13

"Goin where the weather suits my clothes..."