Wet Venting a bathroom.

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Would this layout work as per UPC code for horizontal wet venting? Still, trying to wrap my head around the sizing of the pipe and DFU of said pipe of a wet vent? The reason for this specific routing is I can't penetrate 3" thru the floor joists, reducing to 2" because the wall the vent is rising through is only 2x4 stud.

I have other options but I would want to simplify venting as much as possible.

Screenshot 2021-11-29 081836.png


In the Trades
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Berkeley, CA
The UPC requires that WCs be last on a horizontal wet vent, and Hawaii has not amended that.


So with the layout shown, the lav can wet vent the WC. The lav needs a 2" vent and a 2" drain, and you could maintain the 2" size all the way to the 3" wye where the WC comes in. I.e. you could use a 3x2x3 wye, except those don't exist, so you'd need either a bushing in the straight inlet of a 3" wye or a 3x2 reducer, which could be closer to the wye than you've drawn.

But the tub can't be wet vented downstream of the WC. You'd have to dry vent the tub trap arm separately, before it joins the 3" horizontal drain.

If you have space in the joist bay, you could run a 3" WC drain parallel to the 2" lav drain, going up the page on your drawing. Then the tub trap arm could join the 2" lav drain, and then the combined drain could wye together with the 3" WC drain. That puts the WC drain last, as required, and lets the lav wet vent the tub. There's a limit of 6' measured along the pipe from the closet flange to the wye where the WC fixture drain gets wet vented.

Chees, Wayne
Hey, wait a minute.

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