Venting Challenge

Firstly hello and thanks for any potential help I am working on planning a basement remodel and would like to reroute some DWV if possible to maximize ceiling space. I am in Wisconsin.

In the attached image, the T is a toilet and the V is the main vent; these are 4" PVC. Currently these drop below my floor joist (brown line) and continue on down the green route. I am trying to route these south and avoid dropping all the way below the joist until closer to the cement wall, possibly either by somehow going thru the joist or venting up thru the wall. The floor joists are 2x10 so I think the maximum size that can go thru (horizontally) is 2". One more fixture in play in this setup is a bathroom sink that drains horizontally into V.

Let me know if something is unclear in the picture or if more details would help and thanks again!

We would have to see more than the drawing, because what you are asking CAN require a major remodeling project.

The drain can be reduced to 3" with a 2" vent, but you cannot drill a 2x10 for 3" pipe.

Thanks for the replys, hj is there some other details in particular that would help? I'm not looking for a major remodel so if that is the only way I will probably just box in this area and take the loss of head room.

cacher_chick; right I can't get 3" pipe thru the joist, but could get 2"; do you know if WI code allows for horizontal vents below the floor? I do not believe it does but just thought I'd check.

The other option I am considering is running both the pipe from the vent and the WC drain (possibly reducing to 3") down to the concrete wall, dropping them below the joist there and joining them up. The WC would be vented up the wall it passes under w/ 2". Code seems to allow the fixture to vent distance on 3" to be 12' or 24' (1/4" or 1/8" per foot slope) so I think I am ok from that standpoint.

quote; but you cannot drill a 2x10 for 3" pipe.

I guess that means you cannot put a toilet on the second floor of a building if it only has the commonly used 10" joists. The toilet line could go parallel to the joist to the concrete wall, but your drawing does not give enough information as to what else would have to be done, other than reroute the vent.

hj said:

quote; but you cannot drill a 2x10 for 3" pipe.

I guess that means you cannot put a toilet on the second floor of a building if it only has the commonly used 10" joists.

Click to expand...

Plumbers tend to be the worst offenders of drilling or notching joists beyond what is allowed by the building code.

HJ, the code does NOT allow you to drill a 2x10 for a 3" pipe, and you have been around long enough to know that. The framing can be modified to make it work, but doing it without making any other changes would be an obvious violation.

Note, too, that there are limitations where, along the joist that you can drill holes. For example, you cannot drill one within a certain distance of each end.