Closed Loop Help

[outdrsyguy1]

I'm looking to run a sump/return pump and a closed loop on my upcoming 1000g build. Is it okay to have both flow into the overflow and suck from the bottom of the overflow? I'm going to run an overflow that's going to be 6' to 7' long and external on the backside of the tank. Only problem I'm seeing is that on startup the trough might suck dry if I didn't start the sump return pump first.

Anyone tried that? Or is it a disaster in the making?
I plan on using eductors and a 5,000 gph pump for both pumps. So that's 10,000 gph flowing through the overflow.

 

[enderg60]

It is possible but you need to make sure your overflow can handle the flow of both the return and the closed loop. In 99% of cases it will not work.

Even at 7' long an overflow might not have the capacity for 10,000 gph.

You would have to add up the open area of the overflow(between the teeth) and see if that is capable of handling that amount of open channel flow(Its important to remember to use open channel flow not in pipe flow numbers)

There is also the issue of the amount of noise that much water going through the teeth and the waterfall after them to watch out for.

I personally like to put the suction side of a closed loop inside the tank but use a LOONG PVC pipe with slots cut into it. The one on my baracuda closed loop is 24" long 2" pipe with 1/8" slots cut every 1/4"

 

[outdrsyguy1]

Hmmm. Thanks for the tips. I'm hoping I'll be able to figure out a way to hide all this piping. The closed loop supply with multiple eductors, long return for so much flow. Couple follow up questions.
Reed central overflow calculator recommends 151" for 10k gph which is longer than my tank by about 30" so I guess the closed loop will have to have the return inside the tank. How do I protect the pump from grit and snails etc from being sucked into it?
I also don't want any holes low in the tank to avoid the risk of a bulkhead failure having to fully drain the tank. I guess I'll have the closed loop run through the overflow box but not open to the box. Or I could run it through the tank beside the box I guess since the box doesn't run the full length.