Scott's 270g aka Project Mayhem

[sphelps]

I think you have a little more potential in that sump worth exploring, worst case you're replacing the sump anyway so why not try this first.

1. Add a snorkel to the pump, I've done this lots, usually use long radius ABS fitting.
2. Lower that running water level, I scaled out 3" which I think is easily feasible, maybe even more.
3. Cut out refugium, it'll add more volume to the pump chamber as well so it will have more catch up volume as well during start up.
4. Add a little height to your overflow chamber, ie if it's 12-3/8", can you make it 12-7/8"?

If you can do all that the added volume I calculate is this:

Refugium cut out and lower water level: (27*3+27*2)*13.5 = 1800 in3
Higher E-O-Flow: 0.5*47.5*13.5 = 320 in3

Total = 2120 or just over 9 gallons.

Rough numbers obviously and I didn't exclude the overflow box but you get the idea. I'd also still add a check valve to both return pumps, while it's not a total back-flow issue it will still cut back on a decent amount of water flowing back to the sump (16' of 1.25" Pipe will hold about a gallon).