wet venting bathroom fixtures?

Old 11-03-04, 09:17 AM
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Question wet venting bathroom fixtures?

Our house is new construction; I am a new DIY plumber. I am plumbing a first floor bath with full basement below. The bathroom is tiny (about 6' x 6'). We will have a toilet, vanity and shower stall. The main soil stack will be directly behind the toilet. The furthest fixture from the soil stack will be the vanity. The drain for the vanity will drop to the basment about 5' (horizontally) from where the soil stack drops to the basement.

Twice this week someone has told me to 'wet vent' all my bathroom fixtures. I have done a bit of research on the topic this AM but don't understand yet if I can do it according to code. I don't think I can, but I"m not sure. I"ve lost my copy of Code Check so I'm about to go out and buy a new copy.

Code talks about doing wet venting vertically. ??My question?? Can I run a wet drain line directly from my sink and/or shower to the drain line at the toilet (all under the bathroom floor/in the basement) and then have it vented through the vent stack that rises through the wall behind the toilet? Or do I have to have a separate dry vent line that snakes through the walls from the sink around the shower to the vent stack behind the toilet?

Second question: In the code below, when it refers to 'upper fixture' - how is that defined? All the fixtures are on the first floor. Does it depend on the height of the trap arms for each fixture?

Here's some info I've gotten out of the State of Maine code 6-H:
maximum of 4 fixtures

all wet vented fixtures on the same floor ("...provided, further, that fixtures with a continuous vent discharging into a wet vent shall be on the same floor as the wet vented fixtures.")

"The vertical piping between any two consecutive inlet levels shall be considered a wet vented section. Each wet vented section shall be a minimum of one pipe size larger than the required minimum waste pipe size of the upper fixture, but in no case less than two inches."

"Common vent sizing shall be the sum of the fixture units served but in no case smaller than the minimum vent pipe size required for any fixture served, or by Section 6 D."

Thank you in advance for any help you can provide.
Dawn in Maine
Old 11-03-04, 12:05 PM
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The inspectors in my county want to see a plain old vent if there is any way possible.

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