I noticed an a Habitat house I helped on last year that in the truss/attic space they had routed all the plumbing drain vents into one pipe and therefore only one roof penetration.
Looked like a neat idea. Anyone know what the restrictions on doing this are? Do you have to increase the diameter of the pipe as you add different vents to it? I can’t remember how large the roof penetrating pipe was.
You’re paying for more PVC to run them together, but the fewer roof penetrations I have, usually the happier I am.
jt8
“Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one getting burned.”
— Buddha
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I suspect that this wasn't done traditionally because it's easiest to have CI pipe run straight up. No reason not do do it with plastic, AFAIK. It was done in our house, built in 1976.
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Glancing at the code book, the things that look relevant are:
+ Total cross section area of vents thru the roof equal to building drain size.
+ Vent run longer than 40 ft. must be one size larger for entire length.
Combining in the attic and making only one potential leak sure sounds like a good idea.
Some sort of screen over the big pipe might also be a good idea. Back in my Venice Beach days, I had a tenant who went on the roof and thought it was cute to drop an empty beer can down a vent. Flooded the basement.
-- J.S.
Screen isn't a good idea in frost country. The screen can ice up and block the vent.
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Don't use screen, use hardware cloth (which is "screen" but with coarser squares--the wires can be something like an eighth inch apart on up to a quarter inch apart or more). Is stronger than screen to and will keep critters out. The eighth inch grid may even keep wasps from building nests in the stack, but may also frost up and block the vent (or let snow pile up).
I did it to mine, nothing illegal, only thing its doing is equalizing the pressue as it drains.
I did it to mine, nothing illegal, only thing its doing is equalizing the pressue as it drains.
As long as it all points up, I couldn't think of any problem with it, but I've never used it myself, so didn't know for sure.
But between the trick of running all the vents to one roof pipe and maybe plumbing with PEX... seems like a lot of potential headaches could be removed.
jt8
"Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one getting burned."-- Buddha
If you're in a heating climate, make sure any horizontal vent runs in unconditioned space are well sloped back to the source or the condensate will freeze in them. Same argument as running the vent horizontally through a gable wall.
There are other critter-proofing weather-cap options than screen. Just make sure there's some kind of venting cover on there or you may end up with a blocked drain like my neighbour did. It seems the squirrels liked the sound the walnuts made when they dropped them down his stack, so they loaded it up with over fifty of 'em!