Slotting a tank for external overflow?

[treesprite]

Has anyone here done this who can give info, advice, pictures/videos? Or perhaps just point me to other posts with examples?

I have another thread here recently started - trying to figure out what to do with the 120 g tank I'm working on - and I liked the idea someone gave me about making an external overflow. The tank only has one drain (not including the CL), which just won't do, and I would not mind doing this as much as I would drilling more holes.

This is the tank, before I stripped off the black paint:

The slot would go between the two upper returns, but of course up higher, by the trim.

I made a short external overflow on a 65 gallon tank many years ago, but was only able to do it as a result of me breaking the upper corner of the tank and not being able to afford a new tank. I had to take out the back panel, had a shop cut off the top of it then cut off the broken end. Then I sealed it back on making a sandwich of glass pieces epoxied over the seam, except on that end into which I created an external overflow. I have no intention of taking apart this 120 gallon tank, but now that I have seen an example of slotting the back with a handheld tool, I'm getting kind of itchy. If I end up not doing it on the 120, I might try it on a smaller tank as I usually have a couple sitting around.

Thanks in advance for your responses and assistance!

 

[Lsufan]

There really isn't a good way to go about it. I would suggest drilling about 3 pass through holes & making a narrow internal weir that is only about 1 1/4" wide, then making a larger external box to fit all the plumbing.

If u decide to try & notch the tank I would drill a hole on each end of the slot then all u have to do is cut a straight line from the bottom of each hole. I have read about people using a dremel with a diamond blade but I have tried cutting glass with one before & it didn't work to well.

When I cut glass I use my tile wetsaw with a glass cutting blade is the only way I have found to get a clean cut. Obviously that wouldn't work for u because the tank is already together. If u don't mind buying a few things they do make 4" tile cutting wetsaws that are almost like a skillsaw but it has a water hookup to keep the blade wet. If not u could get a 7" glass blade & put it on a skillsaw but u would have to keep it wet while your cutting.

I would probably first try it that way, drill a hole in the corners then use a glass blade on a tile wet skillsaw. They sell them for less then $100. If not then a regular 7" skillsaw keeping the glass blade wet. The hardest part would be getting the cut started.

 

[uncleof6]

The only way to really do this right is to use a water jet. I used this method for a rather expensive client build. The problem is, it is really difficult to accomplish without creating stress risers, (chips and micro fractures) that could lead to the failure of the tank. I would not recommend slotting a tank that is already built, especially with no prior experience. If something happens, you end up rebuilding or replacing the whole tank, rather than a sheet of glass. After the system was up and running, I felt it was actually a waste of time to slot the tank, and round holes would have worked just as well.

To be fair, there is risk of losing the tank cutting round holes just like with slotting. Cutting holes is less work and less cleanup (of the edges; usually) after the deed is done. The holes should be chamfered, however, to eliminate small chips and stress relieve the holes. This chore is much more extensive with manual slotting; but with a water jet it is a snap, just as with most any other CNC operation. I would also suggest if you are determined to slot, take it to a glass fabrication shop (not a regular glass shop) and let a professional do it. That way it is on them, not you. Even if they happen to have a techni (and many do) they would most likely do it manually, as I doubt they would be thrilled with the idea of a complete tank in the water jet.

 

[treesprite]

I saw somewhere that the person used a Rotozip floor tile bit to do it. I have only experimented in the past cutting small slots in glass from a taken-apart tank using diamond coated cutting discs. I've cut teeth in a glass overflow wall using a dremel and various shapes of diamond coated dremel bits.

Please note that I am just trying to gather information at this point. I know there are folks who have done this, it's just a matter of finding examples and finding reasons for and against doing it. If I don't get enough information of the right sort to convince me to do it with the 120, the idea gets put on my list of things to do with some random small tank in the future (can you resist those Petco dollar a gallon sales? It's always good to have a couple spare 20s sitting around for emergencies or experiments).

 

[Lsufan]

Using a rotozip is about the same as using a dremel. It won't get a clean cut & will probably chip it up pretty good. If u don't do like uncle mentioned & do it yourself, your best bet would be a glass blade on preferable a wet saw. If not then a glass blade on a skillsaw would probably be the next best option

 

[marioensf]

I uploaded couple pics on your other thread; yes it can be done.
One of the images shows the Makita cordless glass/tile saw; the draw-back is battery life; you'd need to re-charge it. Expensive little saw ~$170 but there's the Ryobi option from HD. The round edges are achieved with a regular hole diamond saw.
Finish will not be perfect, go slow, constant water flow.
Use a rubber block with sandpaper to dull the sharp edges.
You could use a diamond router bit 200grit to work the edges; don't know if those are available to obtain a bull-nose edge but you can get a 45 degree chamfer bit to "seam" the glass. Finish might not perfect but hey, it's a DIY thing, right?
Want more images?

 

[Oeste]

I uploaded couple pics on your other thread; yes it can be done.
One of the images shows the Makita cordless glass/tile saw; the draw-back is battery life; you'd need to re-charge it. Expensive little saw ~$170 but there's the Ryobi option from HD. The round edges are achieved with a regular hole diamond saw.
Finish will not be perfect, go slow, constant water flow.
Use a rubber block with sandpaper to dull the sharp edges.
You could use a diamond router bit 200grit to work the edges; don't know if those are available to obtain a bull-nose edge but you can get a 45 degree chamfer bit to "seam" the glass. Finish might not perfect but hey, it's a DIY thing, right?
Want more images?

WOW, that's pretty cool!

 

[Malign Reefer]

Solid work, good job!!

 

[treesprite]

I really like the "cut out" for a smaller tank, but in a large, thick-glass tank, I just have in my head that a slot would be easier (going by the example I saw; I don't have the link, unfortunately).