Basement bath vent check

Greetings again from NC. My project is finally underway. Major delay was saving cash, and then getting the HVAC guys to move units and ducts.

Yesterday I broke the concrete and dug the big hole for the sewage ejector pit. Today is (was?) going to be the DWV. I thought I had a good plan, but then woke up at 3AM sweating over the shower vent. If it is vented, that's the question.

I'll attach a drawing, which may be clear enough. The shower trap arm is to connect to the 3" drain very near the wet wall, and where the sink drain comes down from above. I thought that the sink vent would be adequate to provide venting for the shower, but now I don't. I'm pretty sure that I'll have to put another fitting near the shower trap and run another line straight up to the wet wall to vent the shower. Is this right, or would my original plan, as drawn, work? I'm obviously trying to minimize concrete cutting, and I only want to do it once!

Thanks, as always.

I find isometric drawing much easier to read, and highly recommended anytime you are drawing plumbing.

From what I am seeing in your drawing, the water closet waste is passing the shower drain connection, and the shower is not vented.

If you simply bring the shower drain under the wet wall, the vent can come up into the wall, putting the drain connection to the 3" line between the lav riser and the basin.


I cannot tell what your intentions are for the water closet. The vent cannot be anything but vertical until it is at least 42" above the floor, and you should not use a sanitary tee on it's side or back. A wye is the proper fitting for a vent take-off.

Edit- Same with the lavatory drain. The below-grade connection to the horizontal drain must be made with a wye.

Having lived with and thought about this forever, I fail to realize that the drawing is not completely obvious to one just glancing at it without ESP to figure out what I'm thinking. Thanks for your reply. The drawing is stupid in that the wider horizontal dashed set of lines represents the 6" wet wall. The circles at 2. and 5. are the vents rising up through it, to join above the top plate in the joist space. The 3" drain line starts at the toilet and continues 1-3-4-5-6-7 to the ejector pit. The darker small squares are the steel support posts, and the lighter larger squares are the 2' square footings that I need to avoid!

Thanks for reminding me about wye versus tee for the vent connections.

I figured that much out.

It's not clear how you intend to keep the water closet vent vertical from the main line to the wall.

The shower needs a vent before it makes the connection to the main line.

Don't work on Christmas. :p

Took a break from cutting and breaking up concrete to search briefly for some free or cheap software that would allow me to make isometric plumbing drawings. For a Mac. Anybody have any good program ideas? I looked briefly at iDraw, but wasn't able to determine from the description or App store entry whether or not it would suffice.

I print out isometric graph paper and draw my plans with a pencil and ruler.

"Old School" I guess. :o

What is a "kelly"? Never heard the term. Is that some sort of northcarolina-speak?

Where I live, horizontal santees for vent takeoffs are a no-no, but I've heard they are perfectly acceptable some places. Also, my plumbing
inspectors would make me put a long-turn 90 at #2, because its below the flood level of the fixture served.

You don't really need the vent at "2", but you do need one at "4" otherwise the shower is NOT vented and you would also have the toilet flowing past an unvented trap connection.

What a week; thanks for the replies. A Kelly fitting is my term for a two-way clean out. I must have read it somewhere. And my drawing must really stink, HJ, because my #2 on the drawing is supposed to be the vent for the WC. From the vertical standpipe, a long sweep 90 starts the 3" main drain, which parallels the vent wall. It connects directly to a 3x2" wye fitting (originally as drawn it was a san tee, but I changed it based on cacher_chick's advice). This goes perpendicularly to the drain, and directly to the vent wall, where it turns up with a 2" elbow. I did put in a vent for the shower. Just after the trap, there is a 2x1.5" wye, and then a long sweep 90 to get it pointing at the vent wall under the eventual shower pan.