Vent size?

[rick.a]

What is the smallest size of vent pipe that can be used to go up from the stack and through the roof? Total load is one toilet, 1 lav sink, 1 shower, 1 kitchen sink. I live in MA if that matters.

thanks,

[Tom Sawyer]

You can vent the entire bath group with an 1 1/2" pipe but..... you need to go through the roof with 3" minimum

[hj]

IT is a local code question, but in many cases a toilet needs a 2" minimum vent, and the TOTAL area, NOT diameters, of the vents out the roof has to equal the AREA of the incoming sewer.

[Tom Sawyer]

IPC states that the plumbing sytem must have a minimum of one vent through the roof that is 1/2 the size of the building drain which in most cases would be 4" for residential service so... there must be at least one 2" vent through the roof. However in colder climates state and local ammendments will require the vent to be increased to a minimum of 3" where it makes the roof penetration and perhaps 4" in some places. In my state we have to increase to 3" and that 3" must extend 18" below the roof line and at least 12" above.