What size holes to drill for overflow of 80 gallon?

[sunflashx]

What size should I have the holes drilled for in the overflow of my 80 gallon?

I think All-Glass uses a 1.5" and 1.75" holes for their pre-drilled tanks, are holes this size sufficient?

[scubadude]

Originally posted by sunflashx
What size should I have the holes drilled for in the overflow of my 80 gallon?

I think All-Glass uses a 1.5" and 1.75" holes for their pre-drilled tanks, are holes this size sufficient?

Hi sunflashx
Are you talking about hole size or bulkhead size, usually everyone talks about bulkhead size (the size of pipe that fits in the bulkhead) which Im assuming you are. I think a 1.5" bulkhead would be fine as the ONLY overflow for the tank, but if you want dual overflows I would probably go with 1" bulkheads. Also remember that there are some off brand bulkheads that have a weird diameter hole size. I would definately get the bulkheads first then give them to the person drilling your tank so there is no room for error. Generally a 1.5" bulkhead will require a 2 3/8" hole. Everything evolves around how much flow you want to put through your overflow. If its an SPS tank I would go w/ dual overflows and make them 1" personally, maybe even 1 1/4".

[sunflashx]

What size return holes would you pair the 1" dual overflow holes with?