Okay, either I am over-thinking this, or I actually have a legitimate question. I’m doing a basement remodel, part of which includes expanding an existing lavatory into a full bath. We’re putting a stall shower in one corner. It’s about two feet from a waste stack that serves a bathroom on the second floor. This stack is 3″ cast iron, and beneath the slab it connects to a 4″ line that in turn connects to the main sewer line. The 3″ waste stack from above is vented tthrough the roof.
I have plenty of altitude to get the desired 1/4″ per foot (or more) pitch on the shower drain. My question is, given its close proximity to the existing, well-vented stack, does the short shower drain need its own separate vent? Plan ‘A’ was to just hook the trap arm from the shower drain into the 4″ waste line, fill in the cut in the slab, and be done with it. It seems to me that connecting the shower drain line to a large, well-vented waste line at such a close distance should be fine. But then, the more I read about this, the more confused I get.
Any ideas much appreciated. Thanks!
Replies
What diameter is the shower drain? Two-inch"? What would be the total length of that drain?
Al Mollitor, Sharon MA
It will be a 2" line, 30" long total.
I have a basement sink that drains about 36" beyond the trap, horizontal run, 1/4"/foot slope to a 4" cast iron stack, no vent and it works fine. I sometimes pour lots of water in this sink (it's a slop sink) and it drains away quickly with no gurgling.
I don't know if it meets code or not, but I'm certain your shower will work fine.
MERC
I am not a plumber.
And everytime I look at this I get more confused.
What you are talking about is called Wet Venting.
Now there are two different plumbing codes and one allowes for wet venting, but NOT when there is a toilet above, as in your case.
The other code does not allow for any wet venting.
That said I just reworked a bath in a 1950's home that was setup the same as yours except with a 4" stack. I had to move the toilet and shower around a little. But they had been there 50's and worked so I did not try to do any different venting.