Leaks around vent pipes

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Posts: 144
Joined: Wed Jun 18, 2008 9:00 pm

No matter how many handymen, HVAC techs, or whoever we hire, we keep having problems with leaks around the flue pipe over the furnace room, and the vent pipe over the kitchen sink.

They've caulked with silicone, roofing cement, and one HVAC guy even replaced some fittings and installed a flat square of metal around the flue pipe in our furnace room...but every time it rains heavily, water starts dripping around it, and down our flue pipes.

What needs to be done, to stop these leaks once and for all? I'm tired of having to turn off our furnace/AC every time it rains, so I can throw a large trash bag over the furnace unit to protect it from water damage. Not to mention, it's expensive to keep getting these guys out here again and again, to no avail.

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I used peel and seal ......its a very thick flashing tape with aluminum face and butyl rubber as the adhesive backing. make sure you read up on this product before using it......it works very well , but only if it is put down correctly. u have to get rid of ALL old SEALANTS .....especially silicone or siliconized caulk ...it will not stick to the surface if any traces of it on there. ...lay it down relaxed, not stretching it......pretty much just guide it down with hand being careful to not let any wrinkles form....lay as much of it down in one whole continuous piece, with no choppy end or spare pieces put together. get a rolling tool to press it all down and get any small wrinkles out. the butyl adhesive has to make 100 percent contact with the surface , otherwise water will get under it. if there are any big wrinkles....u have to smash them down.....and possibly make a small split in the center of the wrinkle....then press that down flat....if you are unable to get all the old sealants off......then hit the area with some paint thinner, some acetone..mineral spirits...and anything else u can think of to help break it down........then use a small test piece to see if it adheres. clear pvc pipe glue works pretty well as an adhesive under the tape. but you have to let it dry enough to where it is just slightly tacky....and the peel and seal tape will NOT adhere to anything that is even slightly wet. you will have to routinely check up on this fix....and make sure that it doesn't get loose or come up......because one tiny leak will lead to a big leak , in which case you are better off not having anything on the roof because it then acts as a siphon pouring water into the structure.

as far as roof leaks go, you can pretty much throw all of those sealants in the garbage....they only last for a short time, if they even work at all. roofs shift , contract .....all the time.....basically they shake that mess off.......proper flashing is the only way......and flashing tape isn't an ideal material, but its a far cry better than all those goops.
Steve S.
Posts: 117
Joined: Sat Apr 21, 2007 7:41 pm
Location: Maine

I use a product called PL roof flashing sealant made by Loctite, which I find to be about the best. I inspect all my roof vents annually for cracks and nail head protrusions and reseal where necessary. Be especially mindful of nail heads, which can allow water entry if not completely sealed. Most furnace roof jacks have an adapter added to allow for the slope of the roof...this provides a nice flat surface where rainwater can accumulate and find entry through cracks/nail holes. You may consider installing a replacement roof jack if all sealing efforts are futile.
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Joined: Fri Apr 19, 2013 3:51 pm
Location: s/w michigan

I would get up there and inspect as best I could to start. Be careful and you should be fine. Once you find what is loose, broken, leaking, etc. around the openings then the best plan can be figured out.

Shooting from the hip the rubber collar for the flashing cap may be cracked as mine were.. I used Lucas brand all weather roof repair and has been great. It looks like a can of tar and I applied with a trowel. Use the mesh if needed and you sandwich the mesh between patch layers similar to drywall mud...

Good luck.
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Posts: 144
Joined: Wed Jun 18, 2008 9:00 pm

I forgot to mention, I'm somewhat disabled, so I can't get up on the roof to check things out for myself. So what type of repairman would I have to hire, to get this repair done right once and for all?

I plan on printing out the info you guys have given me on this thread (thank you!), and show it to whomever I hire. So if you could let me know the best type of repairman for a job like this, I'd appreciate it.

Thanks again!
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Joined: Tue Nov 11, 2008 6:12 pm
Location: wisconsin

What type of roof do you have?

Another thought here is water always takes the path of least resistance and flows downhill. I've seen it before where water is leaking inside at one spot but it is getting thru the roof in another spot up higher and traveling down the sheathing or rafters to spot where it is leaking inside. So be sure to double check the area above the flu for possible leaks. It may be getting in somewhere above the flu like at the peak of the roof and then running down the sheathing until it hits the flu and then down the flu to where you see it leaking. Just another possibility that can throw some people off when searching for water leaks. Especially if you have had multiple people out to try and fix this.
Norm Frechette
Posts: 193
Joined: Fri Aug 05, 2011 7:34 am
Location: Norwich, CT

maybe its time to do a complete survey of ALL roof vents and replace them as needed

plumbing vents (similar to this one or equivalent)

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Posts: 144
Joined: Wed Jun 18, 2008 9:00 pm

That is something I didn't think about...that the leak might be somewhere else, and just running down to the part of the pipe that's in the attic, and leaking there.

Thanks for your input, everybody! I'll print this thread out, and give it to the next person we get out here to fix the problem. There's a lot of good info here, which I hope will help them stop this leak once and for all.
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I am with Ponch on this one. If you have had generally competent people out that many times and it has not solved the initial problem, they might be looking in the wrong area. It could even be a condensation problem with the condensation water working its way down to the flue opening.

What kind of roof is it? Composition shingle or metal with coatings and sealants? If this is an old metal roof with severe rust problems, bandaide fixes may be all that is available short of a partial or total reroof.
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