Need suggestions for repairing an HVAC leak.

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New Member
Apr 29, 2023
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Seattle, Washington

Unfortunately, there is a leak in a PVC pipe in my attic. The leak isn't too bad, but it went unnoticed for quite sometime and ended up rotting some of our ceiling.

When we discovered the leak I went into the attic to investigate. I discovered that there was a PVC pipe that extended up through the roof of our house that was leaking at a elbow near the roof. When I followed this PVC pipe from the attic to the floor beneath, I realized that it was connected to our heating unit. I'm not exactly sure what the function of this PVC pipe is or why there is moisture that is leaking from the pipe in the attic. If anyone knows, please let me know!

I have attached some pictures to show you the pipe, where it is connected to my heater, and where it is leaking in the attic. I recommend looking through the pictures in order so you can trace the pipe all the way up to where it is leaking.

If anyone has ideas on how to fix this, your advice will be greatly appreciated!

P.S. - I called the company that installed our AC unit as I know they had to make a few modifications to our HVAC system. I asked them if they could help me troubleshoot it over the phone, but they said that they don't provide that service. They insisted that someone come out to take a look at it for about $200. I thought that was crazy.


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I'd bet you have a boot around the pipe that has dry-rotted from sun exposure. How old is your roof?

The quick solution are these rain collars that slide down over the pipe to direct the water off the pipe, rather than following it down to the first obstruction, the elbow just below the roof. The water runs down the pipe hits the elbow and drops off. I had a roofer install them on my old roof about 5 years ago. The typical boot around plumbing stacks last around 15 years before the sunlight breaks down the rubber. Cheap fix, if you can safely walk your roof. If not, have a roofer come and install them.

When I had my roof replaced earlier this year, I had the roofer install this type of boot around my plumbing vent stacks. Perma-Boots I would not try to install these on an older roof, as the shingles become brittle with age, and you're opening up a can of worms. The rain collars are a perfectly fine solution until you replace your roof. The nice thing with the Perma-Boots is they don't depend on rubber gaskets to keep the water from following the pipe down into your attic. During a normal rain storm you probably won't have an issue. The first time I ran into it was on our old house with about a 15 year old roof during Hurricane Fran. The heavy rainfall made the leak apparent on my family room ceiling on the first floor, it was below the master bathroom shower, and no one had taken a shower within hours of the water spot appearing.
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some times it is very hard to find where the leak originated , I agree sparky, what i would do is next time it is raining get in the attic with some toilet paper and clean off the pipe completely so it is 100% dry , then run dry toilet paper over the pipe and frequently look at the paper , once toilet paper touches the smallest drop it will show as a spot on the paper. then you know if it is a leaking joint or leaking roof.

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