Drain into a stack vent?


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Old 10-10-05, 11:43 PM
L
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Drain into a stack vent?

I know stack vents aren't designed to accept fixture drainage, but I'm wondering if part of one can be converted to do just that. I am abandoning an old basement bathroom and roughing in a new one in another part of the basement. The old toilet was about 2' from the main stack and there's a 2" vent pipe about a foot from the toilet in the other direction. I'm guessing that it's a vent stack that rises from the toilet drain or from the horizontal part of the building drain.

I plan to run the 2" vent from my new bathroom to this vent stack and connect to it in a joist space. No problem so far. Next to the 2" vent is the kitchen sink drain, which turns away from the wall at 45 degrees and then turns down toward the floor about 30" into the room. I would like to cut this pipe before the bend and tie it into the vent stack below the new bath connection. This means the bottom 8' will be a drain and everything else will be a dry vent. The kitchen sink vent is already tied into this vent stack up in the kitchen wall.

It seems to me, the two questions are:
1) Is the fitting that connects the vent to the horizontal drain likely to be one that's approved for a vertical to horizontal drain transition?

2) Since the 4" drain stack has a 3" stack vent and serves only one bathroom group and a kitchen sink, will turning its vent stack into a wet vent hurt anything?

Thanks, as always.
 
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Old 10-11-05, 05:15 AM
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Question 1) no....most likely a santee was used and this is not allowed to be placed on it's back, on a drain. Venting is different from drainage so fittings have different approvals. You will need a wye or combo.

Question 2) Now it's interesting... This will be a local code issue. Wet venting is treated real funny in parts of the country. Where I'm at, no problem, due to the code approved. If your under UPC, there may be some issues.

Check out your local code and ask some questions to a building inspector.

Good luck with your project...
 
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Old 10-17-05, 10:22 PM
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1) That's what I figured. I could argue that a 2" santee would probably handle kitchen sink drainage just fine, but it wouldn't be an approved fitting for the job. Incidentally, both Black & Decker's and Home Depot's plumbing books show santees on their back (but rolled over 45 degrees) accepting a lavatory drain.

2) My county is pretty anti-DIY, so building inspectors aren't too friendly if you can't brandish your plumbing license. Furthermore, our water authority wrote their own code book. I'm using the IRC 2003 since I know the county has adopted that for framing, etc. It doesn't say when a vent stack is required. It just says how to install one. I'm hoping the 4" drain with 3" stack vent is plenty for the one bathroom and one kitchen that it serves. All fixtures are dry vented (except the tub which uses the lavatory), and are above the basement, so turning the bottom 8 feet of vent stack into a drain would not affect any fixtures. It would only alter the effect of the vent stack on the soil pipe.

Thanks for your response. I'm going to keep pondering this.
 
 

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