I am replacing a shower stall in my house and found that the 3" PVC vent stack in the wall protrudes slightly beyond the studs and is in the way of where the new pre-cast shower pan will sit. I could solve the problem by using 3" to 2" reducers to narrow the vent stack pipe to 2" dia. For about 3 ft where it passes the shower pan and then bring it back to 3" dia. To continue up through the roof.

Aside from the question of building code, will this narrowing of the vent diameter interfere with draining of sink or toilet?

Thanks,
Steve

Hi Steve,

"Aside from the question of building code, will this narrowing of the vent diameter interfere with draining of sink or toilet?"

The building code mandates one 3" main vent for each house drainage system. Having said that, the answer is NO, It will not interfere with the venting. Good luck, Tom