What size pipe for durso?

[DanG]

I've got a single 1.25" bulkhead and I am in serious need for a durso. I've been doing some reading and it seems that if you have a 1 inch bulkhead, use 1.25" pipe, but if you've got a 1.5" bulkhead, no need to oversize. What about 1.25?
The return pump so far is doing 600gph, but is capable of doing up to 1000, but that's too much for my sump.