drilling tank overflows and returns

[newsalt1]

Have been kicking around the idea of drilling a tank and have found lots of information on overflows. But very little on returns. Does everyone just go back over the top? Heck I have a drill in my hand already, wouldn't it make more sense to drill for returns also? That said where would you drill for returns/overflows and why? What type of overflows would you do?
Help

 

[pgolnick]

I have never drilled a return. Always worried that if a pump failed (power out) water would flow back into my sump. I guess it is O.K. for a closed loop system. I have my tank drilled with a coast-coast overflow and my returns are over the top of the tank . There are holes at the water line in case of a pump stopping. This prevents water from going backwards.
HTH
Phil

 

[calypso1]

my buddy did a closed loop. it had the overflow and then 2 or 3 returns (bulk heads) off of 1 pump. if your worried about your sump flooding fill everything then turn off your pumps and see how close to the top you are and if can hold more add more

 

[anaelitz]

I prefer the returns over the tank rim. Reason is I can move them if I want to.

 

[scottfarcuz]

I'd think back siphon is the biggest issue. If you have to put them at the top in a place they will be seen drilling doesn't gain much. I think sea swirls, or a wavy sea is a worthwhile investment for return on almost any tank.

 

[newsalt1]

Josh you running sea swirls? I think Kevin is isn't he?

 

[itZme]

Yes and Yes .. I have a 1" seaswirl in the 92g and a 1/2" SS in each of the 75g downstairs that my 92g drains through. I pump the water up to the 92g and then on the way down Josh suggested I use the gravity to have more flow in the downstairs displays so I used them to break up the linear flow of the penductors.

Josh has a pair of 1" SS in his tank for the returns and a couple of regular PVC returns.

 

[newsalt1]

I have or threaded bulkheads that measure 1 3/4 inches across I believe that a 45 mm diamond hole saw would be the correct size for these. My plane is to make a 4 ft long overflow and drill three holes across the back of the tank mounting the overflow with the bulkheads. The overflow would be wide enough to put the bulkheads inside so I could come straight in through the overflow and the glass. Depth of the overflow is still a question. this would be going onto a 72" long tank. They would drain almost straight down into a 100 gal rubbermaid sump. I would then need to pump it about 5 feet to what two sea swirls? Trying to get it straight in my head before pulling the trigger