HOB overflow VS. Return pump FlowRate?

[aznlmpulse]

I'm about to use a return pump (Eheim 1250) that's rated for a little over 300gph with an overflow that's rated for almost twice that much. (Amiracle, single u-tube)

I'm trying to stay away from buying a bigger pump, because I already have 400+ gph going through my tank. Is there any way I can do this safely?

I thought about installing a throttle valve on the overflow drain line, but am little worried that it might cause some serious problems.

any suggestions?

[sjm817]

The overflow does not control how much water goes through it. It only flows back into the sump what the return pump puts in.

[just dave]

The only problem you may run into is if that the water may travel through the U tube so slow that air bubbles may stop at the top of the tube instead of being pulled through and you may get a air lock. If that happens just try a smaller diameter U tube.

[aznlmpulse]

that's exactly what I'm worried about "just dave."

I really didn't want to pay $90 for something and have to swap out a major piece of it to make it work....

I guess that's the only way...

[sjm817]

300 gph may be marginal. You need ~ 200 GPH to keep the U Tube clear of bubbles. Use nice clean return plumbing and minimize head loss. I'd use 3/4" or even 1" dia return plumbing. As mentioned, you can use a smaller dia U Tube if necessary. A valve in the drain line wont help.

[aznlmpulse]

my eheim 1250's disch. side is only 1/2" ID.

would using tygon help minimize head? no 90 degree elbow's or turns.