will this work?

[mikejurasw]

Hey all, I'm mapping out a basement renovation, and want to expand what used to be a toilet-only stall into a small 1/2 bath with new toilet and lavatory sink. I'll need to bust up some of the slab and tie into old clay pipe with 4" pvc, but I have a venting question.
If my new toilet is positioned +/- 4 feet from the waste stack, dropping down into the horizontal waste line downstream of the stack, will that stack function as the toilet vent? (It does, of course, for the toilet upstairs, but that one sends the load backwards to the stack, whereas this basement toilet would send it down but forward).
Crude-ish diagram attached below.
Thanks!
MM

 

[Eddie_T]

Plumbing is not my forte but while I think it would work to vent the basement toilet I am not sure that a slug of water coming down the stack wouldn't siphon the trap as it passes through the wye. Maybe someone with experience would know.

 

[Snoonyb]

Here is a link of the approved fittings and their application, as well as code references; https://www.iccsafe.org/wp-content/uploads/2018_ipc_ess_p68-69.pdf

The problem I have with using the fitting, as well as the placement of the WC in the waste line, is that you will create what is referred ton as "a water primed trap", in that were you to forget to flush the WC on a regular basis, a low humidity area may reduce the level of water in the WC to a point where sewer gasses may escape beyond the trap of the WC, flooding the area.

 

[mikejurasw]

Thanks, Eddie and Snooby. The docs on approved fittings helps. The upper bathroom gets a lot of use; I can see it siphoning out the basement one. I'll find a different spot! Appreciate the advice.
MM

 

[billshack]

this will not work. as someone suggested the flowing water in the main sewer will make a negative pressure and suck out the toilet bowl . However if you did install a vent on the branch pipe between the sewer main and the long swept elbow that would stop the negative pressure.