http://www.reefcentral.com/calc/drain.php
That is a very good overflow/drain calculator that I live by.
For the rest of the info....do you plan to drill the bottom or the back seeing as you have an overflow kit??
This is what I did. It is the simplest and most dynamic way I found. The 45 degree elbo inside the tank is fully adjustable to raise or lower the level of water in the tank or the sump. I put gutter guard on the end of the pipe to keep the pesky snails out of it and to save fish. I just cut a pc the exact size of the pipe and glued it 3 times with clear pvc glue. Through the tank I just used a male and female adapter. I then brought it to a cleanout with a cap on it b/c in the past I have had a problem with venting/gurgling/noise. The way this runs I really didn't need it, but I didn't want to take any chances. I am running 1- 2" drain on each side of the tank. That is almost double of what the calculator recomended for my pump size but I wanted room to grow if need be. I used no overflow. Most of my plumbing was found in black at Lowes and those pcs that weren't black, I painted with
Krylon Fusion for plastic. I had painted a 6" black strip on the back of the tank to hide the plumbing on either side from the front, and to make the plumbing a little less obvious from the back. Oh and I used a dremel for drilling. Slow but cheap and effective.
Chris
