Bulkhead Size

[newsalt]

I have a 180g that I will be plumbing up this weekend. The tank has to overflows with two holes drilled in each overflow. I measured the holes, and the best I can tell is that one is 1-3/4" dia. and the other is 1-1/2" dia. Does that sound right? What size bulkhead fitting should I get? I usually like to get the grey PVC bulkheads from McMaster Carr:

http://www.mcmaster.com/#36895k114/=2fhm1p

If you scoll to "Through-Wall Fittings", I don't see one listed for 1-3/4" dia. or 1-1/2" dia. holes.

 

[THE ROOK]

http://savko.com/PartList.asp?pgid=2&ptid=6

These guys list the hole size next to the bulkhead size. This page is Sch40. There is also a Sch80 page. Those generally use a slightly larger hole for the same size pipe.

Alot of people order direct from this site.