Drilling an older 90
 

I'm thinking of making an older 90 gallon tank into a sump.

I'd like to drill it but there are no indications of weather it is tempered or not.

It has a large (about 12") piece of glass across the centre as a brace. Instead of trying to drill the back for my return pump and have it shatter (if it is tempered). Does anyone think that if I can drill into the glass brace that the back is likely not tempered?

If I break the brace it is much cheaper to replace than the glass back piece.

Anyone with experience in doing this test?

Thanks
-Jeff

Do a search on here for "tempered glass polarized" and on one of the search results is the details for a real easy 30 second test you can do to see if the glass is tempered or not.

Check every pane that you plan to drill. Some tanks will be mixed with one or more pane being tempered and the others not.

I've tried the polarized lens thing but it is really tough to see if I have the correct lighting.

I've had some people tell me that it doesn't always work either.

I guess it'll have to be an adventure.