Glass Tank?

[ididit1119]

I have a glass tank and am wanting to get a drill a whole for an overflow, how can I check and see if the bottom is tempered glass?

[Tommy Gun]

IMO, it is best to assume that it is tempered as most, if not all are. Otherwise, if there is no mark on the glass itself, you may be able to find out from the manufacturer's website.

[jsoong]

I think pretty much all newer tanks over 10 or 20 gal are tempered. If you have an older tank, you might chance drilling a hole, but even then, you might get yourself into trouble.

In general, non-tempered tanks have thicker glass. Eg. my new 80 gal is 3/8" thick, but the old (20+ yr) one is over 1/2". However, I don't think thickness is a definitive guide, so unless you know for sure from the manufacturer, you are taking a chance.