Help with my overflow

[Ratpack]

I have a dual tube HOB overflow that is rated for 1800gph. It came with two 1 1/2" bulkheads, but I reduced them to 1" since I didn't need the 1800gph. My pump will push about 1200gph at the head height my tank is sitting. So it should be close since each 1" line should carry about 600gph. I don't mind turning it down so it is more like 1000gph but I have to keep it turned way down or the pump will drain the sump. The ball valve on the pump is about 3/4 closed in order to maintain balance and I am afraid I will burn up the pump. Any thoughts? Could I be sucking in so much air from the overflow that it is not draining fast enough? Will a durso or similar help?

[King Triton]

On your return line from sump to display tank tee in another line that runs to where your overflow fills the sump then adjust the vavle to get the flow you r looking for to the display tank any excess will return to the sump via the new line teed in befor the valve on the return and not restrict the flow of the pump.

[metalhead]

On your return line from sump to display tank tee in another line that runs to where your overflow fills the sump then adjust the vavle to get the flow you r looking for to the display tank any excess will return to the sump via the new line teed in befor the valve on the return and not restrict the flow of the pump.

Good advise from Triton! This is a great way to moderate over-FLOW!!!

Another variation is to have the T'd line going to a fuge then over-FLOWING back to the sump.

[Ratpack]

Thanks, I actually have the fitting to do this and that was my plan. What really gets me is why can't my overflow with two 1" lines, not come closer to keeping up with the pump? If I had to guess, I bet I am not getting more than 300-400 gph through it.

[metalhead]

Thanks, I actually have the fitting to do this and that was my plan. What really gets me is why can't my overflow with two 1" lines, not come closer to keeping up with the pump? If I had to guess, I bet I am not getting more than 300-400 gph through it.

How big is the line leaving the bottom of the overflow?

[Ratpack]

There are two 1" pvc lines exiting the overflow down to the sump.

[metalhead]

There are two 1" pvc lines exiting the overflow down to the sump.

Are these the same ones you reduced from 1-1/2''? If so why not just put the 1-1/2'' back in? Also, how big and how many siphon tubes are there between the tank and overflow box?

[Ratpack]

There are two siphon tubes on the overflow. The two bulkheads are 1 1/2", but I have reduced them to 1". Even at that, they should flow about 600gph each, right?

[metalhead]

There are two siphon tubes on the overflow. The two bulkheads are 1 1/2", but I have reduced them to 1". Even at that, they should flow about 600gph each, right?

Not sure but it seems to me that the problem may be with the siphon tubes and not the bulkheads on the box...

Maybe try adding a third siphon tube just to see what happens?

You should know if the flow rate leaving the box is inadequate in comparison because water would over-flow out the top of the box in that case.