drilling holes x2

[mixedreef89]

On my 90G RR I have single off set over flow with one 1" and one 3/4" hole. My question is can i drill a second overflow on the bottom? Since there is already one overflow that means my bottom is not tempered right?

 

[uncleof6]

No it does not. The bottom is drilled first, then tempered. You can pretty much figure the bottom is tempered and it will not be drill-able. Beyond that, I would abandon the obsolete RR concept, and think efficient C2C overflow and drilling high on the back of the tank. (More likely that the back of the tank is not tempered.)

 

[KrazyKuch]

you can check to see if its tempered with a flash light and polarized sunglasses