*Drilling A Glass Tank Hole Bigger*

Hello everyone,

I just recently bought an 125 gallon glass aquarium off craigslist.

There are two holes at the bottom of the tank that I want to use for overflows.
But the problem is that the size of both the holes are 1 1/4 inch. And from what I have gotten from my research and from looking around on the web was that there are no bulkheads that would fit that size hole.
And what I was going to do was get a piece of glass to put over the holes on the bottom and silicone them on because from what I read there is a good chance of cracking the glass on the tank if I try to drill the holes bigger. But then I read that what I was going to do with siliconing the glass, the glass would crack anyways ( I'm guessing from the pressure of the water ).
So I kept on looking for ways to drill holes bigger because I ruled out that a wasn't going to silicone a sheet of glass on top of each hole. And I came across on two different fish forums that people used dremels with tile cutting bits to make the hole bigger, but other people used the right size diamond coated hole saw that they wanted for the tank and just put less presure on the drill and let it drill slower and at its own pace.

I need everyones opinions and what they think I should do because I don't feel like cracking this glass. If you know where I could get a bulkhead for a 1 1/4 inch hole please let me know!!

And if you think I should drill the hole bigger please give me suggestions on what size I should make it to.

Thanks,
Tom

 

You could just get pvc 1 1/4 fittings and get another fitting to expand the size to whatever size you need.

 

You could just get pvc 1 1/4 fittings and get another fitting to expand the size to whatever size you need.

You can't do that, the whole point of the bulk head is to seal the hole and to then add pvc fittings onto it for hoses etc... Pvc won't seal it and it's at the bottom of the tank so that wouldn't work.

 

If you can't find anything on-line. I bet home depot or lowes or any plumbing store would have what you need.

 

Here you go: . Seems pretty pricey. Look at home improvement stores. I bet you could find something that works but cheaper. Good luck

 

Wouldn't a 1-1/4" hole fit a 3/4" bulkhead? 3/4" means ID not OD. The walls of the bulkhead and pipe add diameter. If you need more flow you can make a Gurgle Buster which can create a siphon effect effectively increasing the rated flow.

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I think the design of that tank is to utilize two 3/4" standpipes (Stockman or Durso, Durso I think is better). You can install a valve on the primary pipe to control flow.

NOTE: Do not join the 2 overflow pipes. They should independently drain to the sump.

 

HI there

Done it loads of times

Make yourself a 1" thick wooden guide out of plywood, make it maybe 6" square and drill with a wood holesaw a hole that will be a nice snug fit on the outside diameter of the diamond glass saw.
Fix the guide with silicon to the bottom outside of the tank with the guide hole centred around the existing hole, then leave it to cure.
All you need do then is re-drill the hole remembering to use plenty of water and time, DO NOT try to rush a diamond saw through the glass or it will just generate localised heat and stress the glass and........................... well we all know what happens then

Have fun

 

HI there

Done it loads of times

Make yourself a 1" thick wooden guide out of plywood, make it maybe 6" square and drill with a wood holesaw a hole that will be a nice snug fit on the outside diameter of the diamond glass saw.
Fix the guide with silicon to the bottom outside of the tank with the guide hole centred around the existing hole, then leave it to cure.
All you need do then is re-drill the hole remembering to use plenty of water and time, DO NOT try to rush a diamond saw through the glass or it will just generate localised heat and stress the glass and........................... well we all know what happens then

Have fun

Great tip!

 

Just add drill press.

 

Just add drill press.

I think the suction cup guide would be better but there is still a danger of slippage if you're not careful.

 

I Have been working with glass for many many years NEVER drill dry glass it has to be wet and you can get the bits you need from anytimetools on ebay pretty cheap

 

a drill press with suction cup works well but does not allow for a puddle of water around the bit at all times, as dizzy says you never work it dry.
I usually have a hose playing on the drilling area as it keeps it all cool and washes the glass slurry away.

 

Here you go: . Seems pretty pricey. Look at home improvement stores. I bet you could find something that works but cheaper. Good luck

I looked at the site, I clicked on the 1 1/4 fitting in the list under it and is says that the 1 1/4 bulkhead fits a 2 1/4 hole.

Look at this...

 

I looked at the site, I clicked on the 1 1/4 fitting in the list under it and is says that the 1 1/4 bulkhead fits a 2 1/4 hole.

Look at this...

What about this one? . I assume this fits 1/2" pipe. I'm not sure 1/2 inch will fit your needs or not. But I would be hesitant trying to cut the glass. I know it can be done and people do it all the time. I think its a big risk.

 

HI there

If you want the holes/pipes to be used as drains into a sump then 1/2" will be way too small, generally 1" or 1 1/4" bore pipes are used.
1/2" pipe will only drain 200l/hr (52 USg/hr) with a straight drop to the sump, introduce a 90deg elbow and realistically you would be down to 40g/hr which is way to low for a 125g tank.
Here is a link to the catalogue for the supplier I used when I had the store, it gives the max flows through pipe of all the common sizes both pumped and gravity fed, it is in Litres but just divide by 3.78 for US gallons.


Remember when cutting or drilling glass speed is NOT the important thing, keeping it cool and going slowly is, you are not cutting the glass more like you are wearing it away so a 3" hole in 1/2" thick glass will take maybe 10 to 15 minutes to drill, keep the drill bit square and flat to the glass and you will be fine.
Speed wise, for a 2 1/2" diameter bit I use no more than 300 to 400 rpm and PLENTY of water.

If you are going to give it a try go to a glass supplier and ask for some scrap glass from the bin and practice a few times, then, once you get the feel for it you will be more comfortable doing the tank.

If you end up wanting to patch the existing holes then simply silicon some glass of the same thickness as the tank over the holes making sure to make the patch at least 6" x 6" for a 1" hole.

Good luck and don't worry it is easier than you think.

 

Check out this link:

I am overwhelmed by all the fittings they carry. Please know that I have never had a tank big enough to justify a sump and there are many on this forum that have. You just stemmed my curiosity and I had to find an answer.

Good luck to you