AGA bulkheads...

[USC-fan]

Do they use a standard size? What size should i buy?

[tkeracer619]

Yup standard sch-40 bulkheads.

You will have to give us hole sizes to get you the right bulkheads.

[USC-fan]

2in inch hole on the big one. The return may be 1.5in. Not really sure since it wasnt a whole number

[tkeracer619]

Return is a 3/4" sch40
http://www.aquacave.com/075-bulkheads-438.html

Drain is a 1" sch40
http://www.aquacave.com/1-bulkheads-437.html

you might be able to fit a 1-1/4" sch 40 bulkhead but for some reason I can't find one

[RokleM]

you might be able to fit a 1-1/4" sch 40 bulkhead but for some reason I can't find one

Common in SCH 80, however I typically on see SCH40 in 1/2" increments 1" and over.

[USC-fan]

Any advantage getting a 1 1/4?

[RokleM]

More flow capacity, but somewhat of an oddball size and sometimes difficult to find parts for (savko.com local to me has them), especially for true union ball valves, etc.