Does anyone know if it is legal to stub a plumbing vent through the roof and then cover it with a can vent (something like https://www.hardwareworld.com/Square-Aluminum-Roof-Vent-pN7NTQ5.aspx)?
Here’s the situation. I got a call back from a home owner of one of our recent rehabs. This house was partially gutted, but there was a cast iron stack running from an old bathroom in the basement that we never touched (ran through a part of the house that wasn’t gutted and the bathroom is unused.) They had a small leak near the area where this old stack penetrated the roof. The roof is new, and as far as I can tell all flashings etc are properly done.
The stack itself, not the flashing, seems to be a likely culprit. It goes up an exterior wall and appears to elbow into the interior of the house before it turns again and penetrates the roof. I’m thinking that this stack has rusted through or otherwise has a hole in a horizontal section, and when it rains a lot, they take in a little water.
I’m looking for a cheap fix here. I thought of a class b chimney cap, but sticking a can vent over the whole works seems like more or less a permanent fix. But does it violate plumbing codes?
Replies
I gotta parse and vet a little bit. You are concerned with legality here. Is having a hole in your vent piping inside the house legal?
Might not be exactly legal but it isn't really my problem. Nor do I think a small leak in a vent pipe in a ceiling joist cavity a life safety issue. I'm trying to do a cheap fix for a home owner who can't afford much.
Why not just cut the CI, install a fernco and PVC, and call it a day?
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
That's what I'm trying to avoid. It would likely take opening up the plaster ceiling and wall in the room below. Call it a day, sure, but the owner doesn't want to pay for a day.
There are plastic domes with three screws that are designed to correct the problem of rainwater in a plumbing vent.
Checkout your local big box, plumbing supply or a good lumberyard.
.............Iron Helix
Yes, I saw then in Lowes. They look exactly like a mushroom cap and the inside is stepped to fit different size pipe.But he is in MN so I would be afraid of frost blocking it.And his diagnosis might be off.At my folks house they had a leak that can out a ceiling mounted vent fan. This would only happen with strong rains from one direction. Only happened once a year, maybe twice, sometimes 2 years between.Looked in the attic and could not see a sign of leak. Roof was replaced (not just because of this) and still had the problem.One day my step-father was in the attic and happen to see a glint of light. Turns out that there was a pinhole in the vent boot. So small that it was not easy to see. The water would run down the rafter and show about 10 ft away..
William the Geezer, the sequel to Billy the Kid - Shoe
No. Not legal to cut the vent flush with the roof like the photo in your link. The plumbing vent must extend above the roof a minimum distance of something like 18 to 24 inches, depending on you state code. This is to avoid snow from blocking it. You can put a cap on it that is designed to keep rain out but let it vent. If the vent is no longer connected to anything in the house you can completely cap it shut.
Paul
up here we want it as close to the flashing as possible.
snow is not the problem, frost inside the pipe is.
" up here we want it as close to the flashing as possible. snow is not the problem, frost inside the pipe is."......Dosen't compute, why?
"If all else fails, read the directions"
Hot moist air meets cold pipe, frost forms and can block the vent. The longer the exposed pipe is, the greater the odds of frost forming.
Snow covering the vent doesn't seem to be a problem.
I know exactly what you are talking about, its called hoar frost. I don't know what your code is in Canada, but most of the cold jurisdictions in the US require the vent terminal to be increased before it goes thru the roof just for that reason.
Bottom line is it dosen't matter what blocks you vent, hoar frost or snow, you could still end with a non-vented plumbing system by cutting the vent short. It still sounds like a bad idea, sorry.
"If all else fails, read the directions"
All vents must be a minimum of 3" through the roof.
You might do a simple test to pinpoint the leak.
First, run water down inside the stack itself with a hose or bucket. If the leak shows up, it means the stack itself needs a fix.
If things stay dry, then run water on the roof around the area of the stack penetration to see if the roof or flashing is the problem.
Doing this will cost very little, and you won't be playing a guessing game.
Cheap fix -- find the leak and put a saddle & rubber gasket on it. Temporary fix, but "temporary" can last for years, maybe.
Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.