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I am building a 3 piece bathroom + laundry in this old basement laundry room. The cast iron sink pictured drains to the floor and that vertical 1 1/4" copper pipe is a wet vent, I believe, as it is tied into that main 4" stack going across the ceiling.

Basically I'm wondering if I can tie any or all or these fixtures to this wet vent? I'm not expecting any good news as it's a 1 1/4" pipe that is tied in currently but if I could that would be awesome. I'm in Toronto Ontario Canada.

1 Answer 1


If it is, in fact, a wet vent, it's not good for much at 1-1/4" (minimum size wet vent is 1-1/2" and that's only good for 1 DFU.)

If it's a dry vent, it's more useful. Up to 42 DFUs with a 2-1/2" drain.

And it is probably a dry vent, unless there's a sink above tied into it as a drain.

Assuming your applicable code is similar to IPC there's a likely problem in that you can't vent a drain bigger than 2-1/2" with a 1-1/4" vent. And a "three piece bathroom" includes one fixture that usually needs 3" minimum drain pipe.

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