Then, because I do not see any reductions, my own guess is that they're 1" bulkheads. I'd let a few others chime in and give their opinions however, and get a consensus.
When you re-plumb, I recommend glued fittings, in combination with lots of unions.
And, bulkhead gaskets go on the wet side, not the dry side.
I could not tell for sure, but thought they might be. Pretty common mistake. The McMaster-Carr website is a great place to get all one might need, and at a good price - again, just my opinion.