Maybe this will help :)

http://www.lithicimages.com/photos/i...xP3Qn2C-XL.jpg

I thought about that when I first plumbed it but the extra water volume is produced by the sheer volume of water the pump itself is moving into the tank. I can raise the plumbing as much as I want but the pump will still create an inch of water over that height. That inch of water will then make it's way through the system into the bottom sump.

You could add an 90 degree elbow fitting to your return pump with the opening pointed down to allow a lower water level if so desired. I had to do that with a return pump to avoid it sucking air.

Yes, the pic helps! I think you made your sump too short in comparison to the height of the equipment.

I have this on most of my pumps so they can have lower water level.

I would try with some long radius 90's but not the typical 90 elbow. The owners manual for these pumps has a big red X on a pump with a 90 on the intake side. Abyzz doesn't sell the 90 for the intake side like red dragon does. They obviously must not want it used on their pumps. The do sell a slotted 6" straight tube that fits on the intake.

I can only just get the skimmer cup out as it is. Any taller and that would be a no go.

Hmm ok. Is the slotted one only slotted on one side, so you can put the slots on the underside? that might help a bit. I'm not sure if that would give you as much space as you're looking for though.

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).

http://i11.photobucket.com/albums/a1...lps/sump-2.jpg

Thanks Steve, but 9g is still ~2 plus gallons short of accomplishing my goals. I'd rather not spend all the time hacking up the sump, adding height to the emergency overflow, putting snorkels on the pump, etc. That results in me losing my refugium, or more appropriately my water change section. If the water level is already as low as it can be in the pump chamber then I won't be able to set up the water change programming.

Honestly I think a new sump is better than any other option.

Yeah if you got the space bigger would be better. Let me know if I can help, I'll make you an acrylic one if you want ;)