What are typical pipe diameters for bathroom fixtures and do the vent pipes have to be same diameter .

Hi Mattthew Scott

Toilet is 3" minimum (4" is OK, too). Toilet vent needs to be 2" in most states...especially if you are WET VENTING the toilet/tub/shower.

Shower needs to be 2" drain and 1.5" vent if individually venting the fixture...if wet venting you'll use the sinks 2" drain/vent (wet vent) to vent the shower.

Tub drain is 1.5" drain and vent...if wet venting you'll use the sinks 2" drain/vent (wet vent) to vent the tub.

Sink drain is 1.5" with 1.5" vent unless you are wet venting the toilet/tub/shower and then you'll run both the sink drain and the sink vent in 2".

Why do you ask?

Mark