Drilling studs for plumbing

[cedarglen]

I am roughing in my DWV system this week. What size hold should I bore for the 1.5" ABS pipe? I am running through 2x6 studs. By my calcs 1/3 of 5.5" is 1.83". So that is my maximum allowable hole when running horizantally through studs right? Does 1.5" pipe fit through 1.75" holes? I have one spot where I will have horizontal pipe going through a few studs? What do the pros do? 

[MikeT]

Here is a picture of what the pros did on the Oregon Coast.  This passed inspection on a job just down the hill from me.  This is not my project, but perhaps a picture is worth a thousand words.

[ScottA]

It's not uncommon to see pipes installed like that. Not the best practice but it usually passes inspection.

1.5" pipe uses a 2 1/8" hole
2" pipe uses 2 9/16" hole

I've seen 2" pipe run through 2x4" studs which doesn't leave much wood behind. They make metal plates that can be fitted around the holes to restore some of the strength to the studs.

Best plan is to bring your pipes up in a way that cuts down on the holes you need to drill. Less work and less loss of strength to the wall.

[Redoverfarm]

Mike it looks as though they cheated a little by cutting a channel from the face of the studs rather than drilling.  Personally I wouldn't want that even if it would pass inspection.

Normally I try to run all my pipes up through the sill plate to lessen the structural damage.  I don't believe that this fashion weakens the wall as the plates directly under the studs are undisturbed which is where the load is.  Just my $.02 worth