Help with U tube losing siphon

[ellisz]

I have an hang style over flow where I made an internal box from a lee's specimen box and the outer box is from an amiracle overflow. The problem I have is when I shut the power off, it drains too much from the internal box and the U tube eventually loses its siphon.

I have a stockman standpipe in the overflow where I had to have the drain hole cut low to keep the drain sound reasonable. Do I just need to raise the pipe so the drain hole is higher therefore not pulling as much water from the internal box?

I might just try to build another Durso pipe. I made one from 1" pvc and it would not drain fast enough for my mag 5. 1.25" pvc is a bit big for my overflow box. Is there a valve that can be bought at Home Depot or similar to restrict some flow from the mag pump?

Thanks for any tips/ideas!

[fishfreek]

The outside portion of the overflow should have two chambers. One chamber with the drain line and one chamber for the U tube. The U tube should extend at least 1" down below the wall that is splitting the two chambers. This will keep the outside portion of the overflow box underwater. The inside portion of the overflow should extend down into the tank so that the bottom of the inside oveflow box is below the water level of the outside overflow box when the power is off. The inside portion of the overflow should also extend down below the water level of the outside chamber. This will asure that both ends of the overflow remain under water.

If the inside box of the overflow is higher than the outside chamber the water will continue to flow thru the U tube until the water level between the inside and outside chambers is equal OR until air gets into the system.

My guess is that the inside overflow box is to high in the tank and its not deep enough to allow that equilribum when power is cut to the pump.

[ellisz]

My guess is that the inside overflow box is to high in the tank and its not deep enough to allow that equilribum when power is cut to the pump.

I think you are right. I got the overflow with my wet/dry and it did not come with the internal box. I made it work but it is a design flaw Did not think it was a problem until I thought about the power going out and then coming back on while I was not there! This happend once but the siphon held. It is close.

Thanks for your help.