When Drilling the Bottom of a tank

[bored4]

I ordered a custom tank and i am going to drill the bottom myself. I made sure they didn't use tempered glass on the bottom so i could do this. The tank is 48"x18"x12" (long shallow reef is the plan). The bottom glass thickness is 3/8". I was planning on doing herbie style drain. 1, 1" main drain. 1, 1" back-up drain, and then 3/4" return line in a corner overflow.

 

So given all that information, is there a rule of thumb on spacing between holes and distance away from the walls?

[mohawk]

Make sure you have enough room for the flanges of your bulkheads to fit comfortably., Other than that not really.,

[patback]

Read reef gurus comment. I believe it's the 2nd or 3rd post down.

http://www.3reef.com/forums/reef-aquarium-...rium-54340.html

[bored4]

Here's what he said.

 

you forgot one of the most important parts of drilling into glass:

 

here are the minimum requirements in regards to distance for drilling glass

x = 1.5 t

y = 4 t

t = glass thickness

 

measurements are taken from the outer most edge of the hole closest to the edge of the glass.

 

single hole along side: x from edge

single hole near corner: x from first edge, y from second edge

holes next to each other: x from edge, 4t apart

holes next to each other next to edge: x from first edge, 4t apart, y from second edge

 

do not attempt to drill tempered glass

 

x = 1.5 t, does he mean 1.5 x the glass thick ness? so 3/8 glass would be x=9/16" y=1-1/2" ??

[dling]

Here's what he said.

 

 

 

x = 1.5 t, does he mean 1.5 x the glass thick ness? so 3/8 glass would be x=9/16" y=1-1/2" ??

That looks correct. Very cool info.

[bored4]

That kind of seems unsafe, I mean 3/8 glass is pretty strong but only 9/16" from the edge! hmmm.....