Return Pump Question

[hurt]

Originally Posted by fender
Oh and btw, you could have an overflow rated for eleventy billion gph and it will only flow as much as the pump pushes into the tank.
Yes, but your statement only applies to drilled tanks. Try doing that with an HOB overflow and then see if the siphon won't break.

 

[fender]

At that scale probably lol. But On the example given above with 400-500 gph returned and a 600gph U tube HOB overflow... mine never has, ever.

 

[hurt]

I personally find it a bit hard to believe if your return is doing 400gph it's not losing siphon with a 1 inch U-tube. At 500gph, you MAY be fine. So I'd have to guess your return is right at 500gph if it has not lost siphon. Siphons break in the U-tube of HOB overflows when the flows are way off. The water coming into your overflow is going too slow for what it is capable of and the airbubbles aren't forced all the way through the U-tube. So instead they accumulate at the top of the U-tube, and eventually it will lose siphon. You could get around this by raising the drains in the back of your overflow to the top of the intake on the inside of your overflow. This way there isn't a chance for airbubbles to enter the U-tube.