Bath tub & sink - shared vent

I believe in most houses the tub and sink etc. are all vented together right from the bathroom. As long as they don't cause to much "vacuum" to suck the water out of the trap you are fine.

Assuming that there are no fixtures in the attic, yes.

Certainly it is OK to merge the vents in the attic and use a single roof penetration. Note that horizontal segments should be pitched like a drain so that condensation runs back towards the fixture.

As to the size of a merged vent, a 1.5" vent can handle 8 fixture units according to the UPC. A lavatory is 1 fixture unit and a bathtub is 2 fixture units, so a single 1.5" vent is adequate. I see a footnote in my reference that the UPC requires that vents be increased one pipe size if the horizontal length exceeds 1/2 the vertical length.

I assume that there is another vent elsewhere that is the full diameter of the house drain? This is required.

Yours, Wayne

Thanks for all the replies......

No fixtures in attic....thanks for the heads up about condensation drainage, "horizontal" run is about 6' but will follow 8/12 roof line

Wayne...."stacked" bath rooms have toilets with seperate vents that merge in the attic to a single 4" roof penetration...I assume that's what you meant by

cheers

correct me if i am wrong, but in ohio i was told there should be no more than 3 feet between the drains. i am no expert. just check to make sure.

You're probably thinking of the distance from the trap weir to the vent connection (trap arm length). That's different from the OP's situation. Jim

You have good advice from other posters. However, as in all cases you should check your local code enforcement office. National codes are minimum requirements and many localities have more stringent requirements. Your local code may require separate vents thru the roof.

Don Young