Help me with my Sump/Overflow.

[Azazael13]

Over the weekend I finally had a chance to put my 29G sump under my 55. I got everything started fine after a little trouble with the overflow (U Tube style). Didn't realize I needed water on both sides when I was trying to suck the air out, couldn't figure out how people did it :) I am using a Mag 7 for my return pump. I have the return split into a Y with ball valves at both ends of the Y to help control flow and everything.

Here is my problem/question. I am having a hard time getting the return to match the overflow in terms of GPH. The return seems to be winning even though I have 1 ball valve completely off, and the other almost all the way off. Will the overflow eventually catch up and everything will even out? or do I need to keep checking and trying to make it perfect? (those ball valves are a pain to adjust :()

Help?

[KDodds]

The overflow has a limited capacity that you must adjust the return for. It sounds to me like the return pump is too powerful for the overflow. What's the gph rating on the overflow? On the return pump?

[Azazael13]

Overflow is supposed to be 600 GPH, I would need to look at the headloss on the Mag 7 again, but I think it was around 580 (~3 feet head)

[KDodds]

Mag 7.5 is 750gph, thereabouts. You'll need to throttle that back a significant amount. Personally, I'd bump down to a Mag 5. Head loss is virtually nil on small tanks like this, and the Mags are pretty good at low head. If you've more than 3' of head I'd be surprised.

[Azazael13]

according to http://www.advancedaquarist.com/issues/jan2003/waterpipe-v1.xls
I should be about right for my head loss though, which is why I am confused.

[KDodds]

Nope, sorry, doesn't work that way... at least not in practice, in theory maybe. You always, and I mean ALWAYS, should have overflows designed to overhandle the maximum capacity of your pump. OR, planning your pump on your overflows, you should always use a pump rated for significantly less than the maximum rated capacity of the overflows. Just something to think about... if your maximum overflow capacity is 600gph, and your pump's rated at 750, but 600 on the "head loss" charts, what happens if you miscalculate head (which is inexact to begin with) and get 601gph? What happens if the pump really does 575gph? Fine, until the overflow is partially blocked by a dead organism or uneaten food, or algae or whatever. Overflow gets blocked, flow rate goes down just 30gph to 570gph. But you're pumping in 575gph... oops, flood. I'd downsize the pump, no use chewing up wattage with a bigger pump.