overflow and returns question

[darkdrako]

Just ordered my overflow and return supplies and will be drilling my 75g tank sometime next week and just have a few location questions.

The overflow box will be slightly offcentered to clear the center brace approx 2" from the top or so. Where, in relation to the overflow bulkhead should the returns be from the top of the tank? ie should the return bulkheads be higher, lower or equal to the overflow? I was thinking that the returns (hooked up to a scwd) should be slightly higher than the overflow bulkhead to prevent a syphon if the electric goes out.

Most of the other tanks that I have seen look to be an over-the-top return with locline at the end of it.

 

[da5speed]

You can do two things with the returns you can add a one way valve or can drill a tiny whole in the top of the return that will stop a siphon once the water level has dropped passed that hole.

 

[darkdrako]

If they are above the overflow bulkhead I shouldn't need to worry about any siphon because the water will go below the level of the returns and break it right?

 

[jrobbins]

the bulkheads can be at the same level (i assume you are drilling the back of the tank).

to stop the sipon you can drill a hole in the return pipe just below the waterlevel (do a search for "siphon break" and you can find all the info).

or you can just have a big enough sump that it doesn't matter if the return siphons a little....that is what i would recommend, as siphon breaks and check valves can both fail...so long as you have enough space in the sump to accommodate the extra water you will never have to worry about a flood...