Flow, sump, pump?

So i got a sump, uv sterilizer, skimmer, and overflow box.
The overflow box has two drain pipes they go down to the sump there's three chambers in the sump. there's bioballs in the first chamber, then i want to use the second one for a fuge, then the third chamber is where the return pump is. i've also got a pump in the second chamber that goes to the sterilizer, the the protein skimmer and back into the sump. Does that sound like a good order?
I've got it plumbed and everything, but there's a little bit of leakage. Any sugguestions on what to do, the pipes are PVC, can I just use that regular pvc glue from HOme depot?
Also, I've got a 2800 Liter/hour pump as my return pump it's plumbed with a divider that splits; one way goes to the top right and the other way goes to the top left of the tank. i've hooked each side up to the loc-line things, ( i thought they'd look pretty cool). But, there's two problems, the chamber that the return pump is in drains really quickly when i turn the pump on and so the pump starts running only half submerged, would i have better luck running that pump in the main chamber of the sump. And there is hardly ANY pressure coming out of the loc lines. Do i need a stronger pump? please help.
 
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