Drilling Over Existing Hole

[cmcimino]

I recently purchased a used Cad Lights 42 gallon tank, and wanted to purchase all new plumbing for the tank, but noticed the drilled holes are 42 mm and 22mm. I cannot for the life of me find any bulkheads for a 22mm hole, so I am looking into possibly redrilling the hole to a 35mm hole. I am planning on putting a 3/4" SCH 80 bulkhead in the 42mm hole, and a 1/2" SCH 80 bulkhead in the newly drilled 35mm hole. Is it a bad a idea to drill over an existing hole?

 

[redfishbluefish]

It can be done. Here's what I'd do......definitely use a guide for the bit, but also put something (glass, plastic, plywood) below the existing hole and use plumber's putty to seal it to the tank, and also duct tape to hold it in place. This will seal the hole to allow you to fill the guide and hole with cooling water while you drill. Now drill!

 

[JaimeAdams]

You can use such 80 if that is your fancy, but there is absolutely no need for it. Our aquarium plumbing is not pressure rated to be anywhere close to needing SCH 80.

 

[cmcimino]

You can use such 80 if that is your fancy, but there is absolutely no need for it. Our aquarium plumbing is not pressure rated to be anywhere close to needing SCH 80.

The only reason I am picking SCH 80 is because the existing overflow hole accepts the 3/4" SCH 80 bulkhead, based off of BRS.
3/4" SCH 80 SxT Bulkhead Dimensions (see diagram)
A - 59mm/2.32"
B - 71mm/2.79"
C - 41mm/1.61"
Installation Hole Size - Use our 42mm Diamond Coated Glass Drill Bit for DIY installation.

The ABS bulkhead hole sizes are in between.

3/4" ABS Bulkhead Slip X Slip Dimensions (see diagram)
A - 52mm/2.04"
B - 50mm/1.98"
C - 34mm/1.33"
Installation Hole Size - Use our 35mm Diamond Coated Glass Drill Bit for DIY installation

1" ABS Bulkhead Slip X Slip Dimensions (see diagram)
A - 68mm/2.67"
B - 63mm/2.48"
C - 42mm/1.65"
Installation Hole Size - Use our 45mm Diamond Coated Glass Drill Bit for DIY installation

 

[cmcimino]

It can be done. Here's what I'd do......definitely use a guide for the bit, but also put something (glass, plastic, plywood) below the existing hole and use plumber's putty to seal it to the tank, and also duct tape to hold it in place. This will seal the hole to allow you to fill the guide and hole with cooling water while you drill. Now drill!

I didn't think about putting a panel under the existing hole! Might be a little difficult because it's located in a corner overflow but it can definitely be done. Just puddy it prior to putting it down there and taping it pretty good. I also need to double check and see if it's tempered. A glass shop just told me there is a possibility the manufacturer drilled the hole, and then tempered the glass.

 

[don_chuwish]

When I drilled for my overflow I clamped a backing board (plywood) under the glass and the template on top, sandwiching the glass between them. Gives support and less chance of horrible chipping.

 

[lapin]

As "redfishbluefish" said: If you have some plexiglass put that under the hole with some putty to seal it to the glass. Fill the hole with water. Clamp another piece on top of the hole. You can see what you are doing so you know if you need to pull out the drill bit and add more water. Inside the tank is hard to clamp. You can use long pieces of wood and longer bar type clamps to hold down that inside piece. Kinda like this. |_|

 

[Rip Van Winkle]

You can use such 80 if that is your fancy, but there is absolutely no need for it. Our aquarium plumbing is not pressure rated to be anywhere close to needing SCH 80.

+1

The only reason I am picking SCH 80 is because the existing overflow hole accepts the 3/4" SCH 80 bulkhead, based off of BRS.
3/4" SCH 80 SxT Bulkhead Dimensions (see diagram)

The ABS bulkhead hole sizes are in between.

I'd definitely go PVC and not ABS. My advice would be to plan the entire system plumbing, that way, you'll know that everything will fit together properly. The other thing is go with as large a drain as you can. The return size and the drain size that you mentioned seem small IME.

If you don't have a lot of experience drilling holes in glass right now, I'd let Cadlights Aquariums do it for you, as per their posting above. Just let them know what size you end up going with.
Nice customer service, Cadlights

 

[cmcimino]

+1



I'd definitely go PVC and not ABS. My advice would be to plan the entire system plumbing, that way, you'll know that everything will fit together properly. The other thing is go with as large a drain as you can. The return size and the drain size that you mentioned seem small IME.

If you don't have a lot of experience drilling holes in glass right now, I'd let Cadlights Aquariums do it for you, as per their posting above. Just let them know what size you end up going with.
Nice customer service, Cadlights

The drain is a durso pipe that is 1.25", but I'll have to reduce it down to 1". Unfortunately I live in NC so having CAD Lights drill it is not an option. I am shooting for a 600 GPH system, I feel like the 3/4" pipe will have minimal head loss.

 

[Rip Van Winkle]

The drain is a durso pipe that is 1.25", but I'll have to reduce it down to 1".

I've found that 1" is very limiting and doesn't work for me but if that is the way you want to do it, I say more power to you.

Unfortunately I live in NC so having CAD Lights drill it is not an option. I am shooting for a 600 GPH system, I feel like the 3/4" pipe will have minimal head loss.

Gotcha.
Yeah the plumbing should be adjusted for the existing return pump.