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A Plumbing Vent Question

Kwan_Choi's picture

I made a conical cap out of sheetmetal, attached some legs and fixed it to the vent with band clamp. To stand up to the snow, use heavier gauge metal and use a short length of cast iron pipe for outside of the roof.

(post #176854, reply #10 of 11)

I'm helping a friend on an addition to his house. He's got most things planned out but a waste vent for the plumbing in the addition. I'd go through the roof except we live in an area with high snow load and the roof from the existing house dumps on the addition's roof. Judging from other houses in the area with vent stacks low on the roof I don't think it would last a winter. Many homes in the area vent out the side but I'm not sure how kosher that is. Things like, how far from the eave and how far from a window or if it meets code in a place that has codes (we don't yet).

Any advice on this or techniques to protect a vent stack through the roof is appreciated.

Kevin McD

(post #176854, reply #1 of 11)

Kevin: I had the same concerns as you because we got 6 feet of snow in 98/99 when we were planning our house. You could frame around the vent and side that, like those "chimneys" with the metalbestos flue pipes inside. Or there are little metal snowplows for penetrating pipes to support them and to split the oncoming avalanche. You can also run two metal bars up at 45 degree angles to add more support to the pipe. If doing that and you use metal as you turn to go through the roof, it will be easy and really tough. The metal vent pipe will be secured at the roof sheathing and maybe 2-3 feet up where the straps tie it to some rafters above it. It won't go anywhere. Sizing - your vent cross section has to equal or exceed your drain cross section as measured through all plains. You can switch from a 4" to two 3"s and back again. Or from a 3" to two 2"s and a 1-1/4". I opted to do that to avoid blasting through so much of my top plates. And your vent pipe(s) has to equal or exceed your drain pipe (for the addition, in your case).

If you have composition shingles on a less than 12:12 roof, it is very unlike to slide. If you have a metal roof, reinforce that vent pipe. I have composition, 12:12 (nothing slid its first year) and used ABS, but ran it toward the peak of the roof, within the rafter bay so there's not much snow above it. But it sounds like that is not an option for you. -David from Kenai, Alaska

(post #176854, reply #2 of 11)


You might also check with the powers that be if a Studor vent would be allowed in your area. This is basically a non-return valve perched atop a vent pipe and NOT penetrating the roof. The valve must be in an accessible location ( attic, wall cavity with access, etc) just in case it must be replaced.

(post #176854, reply #3 of 11)

Hey Kevin! I've used a small air admittance valve under sinks where no other options are avalible, but here in ohio air admittance valves ( Studor vent as Ralph called ) are illegal. Reason being is that if the rubber flutter valve goes bad, who's to know until sewer gases have filled the home.

K.I.S.S. method! Keep It Simple Stupid. Try to run the vent closer to the ridge of the existing house. Side vent would be sightly and a chase for a stink pipe is an overkill! Depending on your fixture count 1 1/2 pvc vent stack may be all you need !
Good Luck Mark

(post #176854, reply #4 of 11)

My first comment would be, where are the vents placed now? Why wouldn't you just go into the attic/roof space and tie into the existing soil stack? It is a little more labor, the AS would cost about $20, and you would have fewer penetrations through the roof. Works for me.

I am not a believer in putting vents straight up into the roof at every bathroom, so your roof looks like a porcupine. The fewer penetrations the better.

(post #176854, reply #5 of 11)

I agree with Scooter ... hey, is the risk with sewer gas that it will actually kill, or merely nauseate, you? Not willing to try it out myself.

There is a freezing/blockage hazard with exposed side vents.

(post #176854, reply #6 of 11)

I would love to connect to the existing vent but it is over on the other side of the house. Also, the existing house is a clearstoty without any attic space, to connect to that vent I'd have to go through the ceiling of the existing house. Not an appealing prospect.

I'm leaning to running the new vent as high on the addition roof as I can to minimize the ammount snow that can slide into it. Still, the roof of the existing house can hold 3-4' of snow before it slides on to the addition and into the stack. Thanks for the advice though.

(post #176854, reply #7 of 11)

I suggest you talk to the inspector -- this has surely come up before, and it would help to get advance approval.

Sliding snow can be a big hazard to life and limb and framing. You may need them snow anchor thingies (can't remember the name).

(post #176854, reply #8 of 11)

Apparently those plumbing vents are not just to vent out that nauseating smell. Apparently sewer gas can be quite volatile and many homes paid the price back in interior plumbing's early days.

(post #176854, reply #9 of 11)

I cant state this as fact but a guy I used to work for said his brother-in-law and a coworker were killed, pretty much instantly while attempting to pump a septic tank.

This was in Minnasota [sp?] and the tank was buried pretty deep, to avoid freezing I guess. He said they dug down to the tank with a backhoe and his brother-in-law went down a ladder and pulled the lid off, took one good breath and collapsed. The coworker then went down to help him and also collapsed.

(post #176854, reply #11 of 11)

I made a conical cap out of sheetmetal, attached some legs and fixed it to the vent with band clamp. To stand up to the snow, use heavier gauge metal and use a short length of cast iron pipe for outside of the roof.