Glass drilling and structural integrity

[george]

Does anyone know enough about the materials properties of glass to comment on how drilling a hole in the center of the bottom of an aquarium affects the structural properties of the glass vs. drilling near the edge?

I know glass bows (obvious from tank ownership), but I came across a very unusual hex glass tank that's center drilled and wondered how it would hold up if the hole were widened from the 3/4" bulkhead hole (whatever size hole that requires) to a 1 1/4" bulkhead hole to increase flow.

 

[jetchris]

Once the hole is reinforced with a bulkhead I would think the integrity would not be comprimised very much

 

[jeff_mcphail]

If the hole was drilled by the manufacturer of the tank then the glass was most likely tempered after the drilling process. once the glass is temperd it will most likely break if you try to drill it again. if the glass is not tempered then it is possible to drill the hole out larger. Use a a schedule 80 bulkhead and drill the hole out to fit it perfectly so the bulkhead has as much gasket surface area as possible for added strenth.

 

[jeff_mcphail]

Chris, you the man! :up:

 

[george]

The tank was definitely drilled after manufacture. The original setup has 3 holes in total. The one in the middle is about 3/4" and was used to run power up to the hood for lights (I guess they wanted a cord-free look) and the other two, which are about 5"-6" on either side of the center hole were drilled for a canister pump intake and output. I plan on using those holes for return lines.

The tank is a 60 gallon hex, but not the same dimensions as newer ones. It's only 23" deep and is about 28" flat to flat and 32" corner to corner. Symetrical. The build quality seems Oceanic-like, but I have no info on the actual builder nor does the guy selling it.

 

[ckwatson]

that sounds like a pretty cool tank. Is there a "over flow" in the middle of the tank that would hide your drain and returns or is it open?

 

[george]

No overflow in the middle, just holes. I've pondered getting a 4" black pvc pipe and making an overflow for it. However since it wouldn't be bonded to the glass bottom, only stuck on with epoxy, I'm not sure how well it would stay in place with all that water moving around.

I'm in the very early planning stages on this. The only thing I was sure of was that a center bottom drilled tank like this would be cool looking.

 

[ckwatson]

I think it would be as well, you could build the rock work up around the returns and drain and have a 360 view.