Is it OK to use an 1 1/2" drain line if I have plenty of slope? Under the house it is 1 1/2" that I have to tie into. How far away is the max for the vent pipe?

In a case of have to a 1 1/2 pipe will work if that is all you have to tie into but if you are getting an inspection you may have to use a 2 inch line. The trap needs to be within 30 inches of the vent pipe.

In a case of have to a 1 1/2 pipe will work if that is all you have to tie into but if you are getting an inspection you may have to use a 3 inch line. The trap needs to be within 30 inches of the vent pipe.


I thought the standard is 2" not 3". Maybe I misunderstood your answer.