Po mans overflow

So do you mean to drill a hole in the bottom of the tank for the overflow (ie. standpipe) or do you mean like the hang on overflows that go over the edge to the outside of the tank?

I'm not sure with the hang on overflows, but with the standpipe, restricting the overflow with a valve or similar is not a good idea. If the return pump gets slightly out of whack with the overflow rate you can end up overflowing your whole tank. You are better off letting the overflow flow its natural amount and restrict the return pump output to match. This way the flow through the standpipe is regulated by the head pressure on it. If the head pressure increases (ie tank water level raises) the flow rate of the standpipe will increase to match(within a range of course). With a valve restricting the overflow rate, if the tank water level increases the standpipe cannot flow more to keep up and the tank will eventually overflow or at the very least pump your sump dry

I have internal corner overflow and use a modified 'dorso' standpipe. This has an air valve that allows you to slightly fine tune the flow of the standpipe but its mostly to prevent a syphon effect with my design. I combine this with a ball valve on the return pump line to restrict the return flow. It works quite well but I still am getting a lot of noise from the trapped air in the drain pipe from the overflow.

Are you asking if you can glue together a "U" shaped tube out of pvc and run it to your sump? If that it the question, then the answer is no, you must have a box inside and out side the aquarium to keep the "u" tube primed and to controll how much water is removed from the aquarium. That would be like putting a drain hose in the aquarium.

Was that the question or did I not understand it correctly?

I was curious about doing something like this too.As my hob aquamaster needs 4 x1/2"siphon tubes to keep up with its pump output, I dont understand what would be th difference if I plumbed those same tubes to a sump instead.I dont understand how a hob overflow would improve this particular application.Can anyone throw some science at us here?

THis would not work very well if at all. THe problem is that there is nothing keeping the "U" tube primed. In fact you would have a very time getting it primed in the first place. (primed means the "u" tube is full of water.) THe "U" tube must have both ends submerced under water at all times to keep it self primed. What would happen in the case of your drawing, assuming that you could get it to flow water (wich you probably could) the down tube going to your filter would gravity drain water out of the tube very quickly so eventually there would be an air pocket at the top of the "u" tube. Your drain will remove water faster than your pump will add water to the tank (in properly designed systems it will). THis is hard to explain properly but I am right on this. (i spent many years trying not to pay money for an overflow box) THis is not an area to skimp on, you will have a flood if you don't get a good design.

What size tank you have? I may have a few spare boxes I could part with pretty cheap.

I agree with ornatapinnis.

You can however drill a hole in the pvc (inside the tank) below the water line. That will keep the tank from siphoning too much water out of the tank.

you could use that idea only if you had a hole drilled thew the back of your tank below the water line then you don't have to worry about priming you can drill thew the back the only piece that is tempered on your tank is the bottom i did my tank like this and there are no probs been running almost 2 years

Clay said:

I agree with ornatapinnis.

You can however drill a hole in the pvc (inside the tank) below the water line. That will keep the tank from siphoning too much water out of the tank.

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Your Idea is correct for a return line to prevent back siphoning. THis guy is wanting to use this as a drain to a sump.

Good point though, it's important to have a siphon brake on your return line.