Need some plumbing advice.

My return is drilled through the overflow box about two inches below the water surface. To prevent siphoning my tank back into the sump I'll drill a hole in the return line in the overflow box just below the surface. I get that, but the one thing that confuses me as I'm filling the tank is should I make sure the return inside the display tank go below the level of the return hole? Otherwise as I'm filling it all the water is just going to go into the sump regardless of siphon break. Everywhere is out of loc line so I have to do it temporarily with pvc and elbows.

Why not put a check valve in

I probably will do that as well. But I don't want to rely on that just in case you never know.

http://i866.photobucket.com/albums/a...ps2u6h6dub.jpg

Here's what I mean, if you left it like this with no check valve all the water up to that level will be drained. I'm thinking the line should be curved down to below that level (kinda like a durso) that way the siphon break will prevent water from draining below that level?

It will still drain down to the lower part the pipe regardless if you put a elbow on or not it just won't siphon

http://i866.photobucket.com/albums/a...pspipvthaw.jpg

Something like this?

mine return is similar, just have room in the sump for backflow

Really want to avoid the back flow to the sump if possible.

What if I angle up on the return and create a siphon break on the pipe on the display tank side?

Put 2 x 45 fittings
on the return bulkhead , first one aimed up the second aimed out , this wouldn't be permanent but something to use until the loc line is available , don't glue the 45 just dry fit. This will give you the raise you need ;)