This is a question for ScottA, or anyone with experience in running DWV lines:
I have a basement toilet that is the endpoint of a 3" lines running to my septic. It is vented by a 2" line going up the wall behind where the toilet will go. Right next to that vent pipe (not fully extended yet) is a 3" DWV pipe that drains the toilet on the main floor, and it runs into the 3" line almost immediately downslope of my basement toilet.
So here are my venting and drain questions for this part of the setup:
Can I have my vent for the basement toilet run into the 3" line that serves as the waste drain for the toilet on the main level? Can it connect between the floors (below the main floor drain) or must it connect above the main floor toilet?
Also, on that same setup, I assume it is okay to drain the main level bathtub into that 3" line with a Sanitary Tee?
Thanks for your help.
mt
MikeT I am sure the resident plumber will pick up but IMO if the 3" is vented at or near the end of it's run on the upper floors it should work. But what do I know at the cabin I still using trees.
I'm sure you can't run it below the waste coming down from above but you could run it to the 3 inch back above the upper waste inlet where it also becomes a vent- take the 2" up above the main level and tie it into the 3" vent stack - you can't wet vent (except under special conditions that are best ignored due to different interpretations of what is allowed).
...and Scott is better than me on this but I think I'm right.
Vents need to go to the outside dry.
Can you trace a path from the fixture the vent serves to the outside with no water flow in it?
If you want to connect 2 vents together serving fixtures on different floors the connection must be above the flood level rim of the upper fixture.
Since the main purpose of a vent is to protect traps from being siphoned each trap should be vented before connecting to a waste line serving other fixtures.
There are exceptions but they involve engineered solutions on a case by case basis.
As a general rule no wet venting is allowed. So yes Glenn is right.
You can tie in the tub to your 3" waste line but remember it must be vented before connecting to that line unless there is no fixture above it and the 3" line is vented.
Plumbing can be tricky so best to study everything carefully until you understand how it will work. Ask if you have more questions.
In that application a wet vent probably isn't allowed. It depends on the plumbing code. I know some jurisdictions allow 1 or 2 wet vent applications. Its ok, some places to drain a small fixture thru a toilet vent, like a lavatory. I know code here allows 2 wet vents per structure.
Thanks, folks. I kind of figured I needed to run the vent pipe up through the floor, parallel to the drain, and then connect it above the main floor fixtures, but I was trying to see if there was an easier way that used less pipe.
I think I will be okay if I run my vents up and connect them midway on my main floor, and connect my drains into the 3" lines below.
mt