I am putting in a basement master bath. I am confused as to how to use a common vent for the Toilet and Bathtub.

Toilet is 3" Tub is 2". If I vent the toilet with a 3x3x2 T and the Tub enters just below the 3x3x2 T with a 3x3x2 Wye would the Tub be vented?

Or do I have to vent the tub before it gets to the 3" line?

Please help a novice plumber

Hi Hans, If you are planing a lavatory for your bathroom group then vent from the lavatory and pick up the tub off the lav drain before it ties into the main. That will vent the entire group. If it's just a tub and toilet then pick up the tub downstream from the 3X2X2 vent tee. More questions? I'm as close as a click. Good luck, Tom

Wow, Quick Response!

However, I'm somewhat confused... When you refer to Lavitory is that a sink?
I think you are saying run the Tub with a 2x2 wye into the 2" vertical vent for the sink then into the 3" horizontal pipe? I'm not sure I have enough room to have the 3" pipe 2-4" below the 2" drain.

I guess I need to divulge more details....This is a full bathroom (sink, shower, whirpool, toilet) in a basement addition. I'm too far from the existing main (septic system) so I'm putting in a sewage ejector.

My problem is getting to an interior wall to vent.

My plumber friend tells me I need to vent the Tub within 3 1/2 feet assuming 1 1/2 inch lines. The overflow for the whirpool is 1 1/2, but I purchased a 2" trap, hoping this would let me vent the tub within 5 feet.

Minnesota code says the Toilet must be vented within 4 feet. I could vent the toilet in a wall if I curved the 3" waste pipe away from it's eventual destination.

What I thought we could do was to put a column in between the tub and toilet to hide a vent. We were going to put a glass block wall between the tub and toilet anyway. THe column is designed to hide a 4x4 post, so I don't have a lot of room.

The shower is 2 feet from an interior wall, so not a problem.

If I vent the tub just before it gets to the 3" line, the toilet would be vented through the 3x3x2" wye which I don't think would be acceptable, because a vent must be 45 deg or greater, and the wye would be close to horizontal.

If I vent the 3" line, and pickup the tub with a 3x3x2 wye just below, the tub would be (If I understand) wet vented for the foot or so back to the 3x3x2 T.

Still confused...

Lavatory=Sink. [If I vent the 3" line, and pickup the tub with a 3x3x2 wye just below, the tub would be (If I understand) wet vented for the foot or so back to the 3x3x2 T. ]  That's correct.  Since you're going to have to vent the lavatory why not connect the whirlpool into the 2" lavatory drain.  Not the lav vent.  that will get  the whirlpool wet vented.  your tub ties into the 3" downstream from the vent.  The lav and whirlpool are vented through the lav vent and you could revent back on one of the vents to the vent you're taking through the roof.  Do not drop your pipe size below 2".  that gives you a 5' run and 1 1/2" chokes your drainage down.    Cheers Tom