Hey Guys,
I’m doing the plumbing for my father in law’s basement addition. We’ve got a bathroom backed up to a kitchen using a common 2×6 plumbing wall. The kitchen sink drain will be about 19″ to the right of the single bowl vanity drain, which is about 2 feet to the right of the vent continuously running through the main floor wall out the roof.
My question is whether I need to use a separate vent for each drain, or does a single vent between the two accomplish the task? Or a single vent to the left of the bath drain (even better for me)? Since it’s all so close together I thought it might work. It’s all 2″ pvc.
Thanks for helping,
Dog
Replies
Starting with the fixture farthest away from the main vent, install your waste line and go up with a vent line. This vent line should raise to a level above the flood plane of all fixtures on either side of your chase wall and then 90 over toward the main vent. As this vent crosses the next fixrure in line, you tee up from that trap/ waste line and into the crossing vent line.
Since you only mentioned two sinks, a 2" crossing vent will be fine. The number and type of fixtures using a crossing 2" vent , and the lenght of the vent run is limited by code. Adding a shower/tube would also be ok, but a toilet must be vented by a pipe no smaller than the waste line serving it. That is why most plumbers vent the toilet with a 3 or 4' stack , and then tie the other fixture vents into this main vent.
Make sense?
Dave
thanks Dave,I got lucky when you replied. You've helped me with plumbing stuff in the past that also worked well.Yes, that makes sense. I built this house about 7 years ago and had a good plumber rough in the basement. He has a stack further to the right that takes care of the tub and toilet, utility sink, etc. but left me a vent stub coming down from upstairs in the joist cavity, just right for venting these two sinks.I think I'm getting a sense from you that venting to the far side of the farthest sink from the vent will help draw air through the whole system better?
I think one of the engineering type guys can give you the physics of a drain better than me, but "drawing air" is a good analogie.
Without good venting practices any drain will air lock at least temporarily as a fixture drains. Kind of like turning a bottle of water upside down quickly. As the intial rush of water leaves the bottle, it creates a vacum behind (above) the water remaining in the bottle. The vacum will hold the remaining water in place until the prssure on both side of the liquid equalizes. That is the gluge or gulp of outside air you see or hear when the pressure equalizes by sucking air into that vacum space.
Same thing can happen with an improperly vented line, and you get slow running drains that clogs up easily. The equalizing pressures is just one of the functions of a drain vent.
The other purpose is to release sewer gasses outside of the building envelope. This is a major health and safety reason for vents.
I bought the Taunton Press book "Code Check- Plumbing" off this web site. When in doubt I look there first. If I am still confussed I call friend that is a master plumber.
So far I have passed all my plumbing inspections on my shop and house. I do enough plumbing repair stuff at work that I want to get it right the first time for myself.
Dave
A typical bath including toilet can usually have a 2" vent riser. I don't have the chart in front of me but there are some exceptions for really long runs or long horizontal runs.