I have a synergy reef sump which has 3 1.5" bulkheads. Is it standard practice to glue the pvc directly to the sump's bulkhead? I will be using unions so I can still remove the sump if needed.
That is assuming that your sump bulkheads are on top and not on the sides, which I'm sure synergy's are on the top most, if not all sumps are. I guess really it would be up to you, I've never had an issue with my bulkheads not being glued. I get a little salt creep ever now and then, but if you're putting unions on, I guess it wouldn't matter if it was glued.
I didn't glue mine for reasons of disassembling and me constantly changing stuff and trying to improve certain things.