Will this cause a Backsiphon issue?

Hey Sue.. if you go the check valve route, get the one with the ball in it, not the flap kind. I had one that was very reliable for years. Jason got one recently and he likes his.

Nice one Boomer. ;D

 

you could also use a overflow box for the intake and it will stop against an overflow in power outages.

 

[quote author=hottielover14 link=board=General;num=1086917444;start=0#11 date=06/12/04 at 17:14:43]you could also use a overflow box for the intake and it will stop against an overflow in power outages.[/quote]

Yes that will stop the siphon for the intake but it will not stop it on the output side if the out put is below the water line.
You would have to drill a hole in the output line just above the water line on the inside of the tank.

 

Hey! Love the diagram! It is exactly what I had in mind!!! No one has commented on whether or not it would be HELPFUL for circulation to put the out put down low inside the tank......as opposed the the standard higher up output...
The benefit would be more current from behind the live rock where you can't really get to a powerhead to clean it etc. Is there a benefit to this? Or am I just making extra work for myself. Do I count the downward piping as extra 'feet of head" or does gravity take over.....THANKS FOR ALL THE GREAT COMMENTS!!!

 

I think what you have planed will work fine, I think the main reason most people put the return above the water line is to keep the surface of the water mixed up so you don't get a film on the water surface. But I think ( And I may be wrong ) : ;D but if you put your protein skimmer in a sump under the main tank then you would not want the surface water mixed as the skimmer for the overflow will take the film off the water and bring it to your protein skimmer were it will remove the scum rather than mix it up into the tank water.

This is what I did in my tank.

 

Hey ! Now that is different! Pretty cool! Thanks! 8)