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Adding bottom/back drains.


richms

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Want to put a sump under a 3 foot tank, so need to drill the bottom.

What is the prefered bulkhead fitting to use for this. I had a look at miter 10 for some and saw nothing that looked suitable. Idealy I would like to be able to screw a coupler on the end of some 40mm pipe into it, possibly would settle for 32mm, no smaller tho.

I would want one for the back that turns a corner pretty quickly as I dont want to have the tank more then 50-60mm out from the wall. Anything suitable?

Secondly, assuming I buy one of the diamond holesaws off trademe (like http://www.trademe.co.nz/Jewellery-watc ... 538026.htm ) - what is the process to use it? Just whack it in the cordless and start drilling or do I need to use some lubricants etc.

How far from the back edge of the tank does it need to be for safety, and is just regular silicone suitable for gluing it into the hole or is there something stronger that will lock it in place better and stop it trying to turn when things are screwed into each side of it?

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The proper fittings are "Hansens" and they make them in many sizes with varied connections. These units have a 1cm lip on them complete with rubber seals. Recommended to double up with silicone anyways.

That's all I'm comfortable giving advice on, hope it helps!

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Secondly, assuming I buy one of the diamond holesaws off trademe (like http://www.trademe.co.nz/Jewellery-watc ... 538026.htm ) - what is the process to use it? Just whack it in the cordless and start drilling or do I need to use some lubricants etc.

We bought one of the diamond holesaws a while ago and they work great provided you ensure there is heaps of water around for cooling. We found that the best way to do it was to make a circle with your thumb and forefinger and use this to locate the bit where you want the hole, wet the area down, and give it a burst on the drill, about 1/3 speed. When it has made a groove, remove your hand and direct a steady stream of water over the cut - you will see a white liquid running away from it. Keep the drill at right angles to the glass or it will grab and the glass will crack. :o

If you do not use enough liquid, you will see white powder forming around the hole and your drill bit will last about three holes.

Don't apply downward pressure to the drill bit. The weight of the bit is more than enough, let the bit cut through the hole instead of being forced through, and make sure the glass you're drilling is supported on both sides of the hole. A donor piece of wood under the entire piece of glass is good.

It is possible to drill tanks that have been built - I think it's a little easier as you don't have to worry about the glass being evenly supported.

Just remember, heaps of water, slow to medium speed, and each hole will take around 60 to 90 seconds to drill (thru 6mm glass). :D

I guess the best thing to say is practice on some donor pieces first, so you can get it right before working on your pride and joy. :wink:

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You need a plumbing outlet rather than Mitre 10. Go to your local Mastertrade and ask for a 'tank fitting' - in the States its called a bulkhead. Hansens make tank fittings and there are other brands around as well. Mastertrade stocks Hansens though. I found that Mico and Plumbing World (at least where I am) didn't carry much in the way of PVC fittings.

I used 25mm fittings and the tank fitting and the elbow was just under 9cm from the glass. The fittings for 40mm will be bigger but you should be able to trim some off the elbow but that still won't get you the 5-6cm you are looking for. I don't know of a shorter way to do it.

For drilling the tank I went to Super Auto Cheap and bought a $20-$30 rotary tool with accessories that included a diamond bit. I took the tank outside, put it on the ground, ran the garden hose on it with one hand and drilled with the other. Minutes later I had a hole. No practicing. Maybe I was stupid and just lucky but I had a hole and a rotary tool that has proved really useful for other stuff as well.

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Since the day of that post I've spent a whole day drilling holes for tank fittings (Hansens) in glass. We used a drill press with a nifty little attachment worth about $400 that puts a blanket of water over the drill bit as it spins, but a person sitting with a pump sprayer or hose letting a stream of water on the glass might do the same thing, sharronpaul seem to have had success with this method. One thing not mentioned previously is that if you're dealing with anything over 4mm thick you'll need to flip the glass and finish the hole from the other side to prevent chipping. If you're off by more than a mm with this drilling from the other side, the glass will prolly crack and break.

With the clearance mentioned, heather is right, you'll need about 10cm at the back of the tank for a standard fitting. Best to drill from the bottom and use PVC pipe to get to the desired levels.

In the end, I'd take my glass down to the local glaziers and pay the $5-10 per hole drilled. Hang around and watch what they do and give it a try next time (if there is a next time) before spending big money on bits and bobs for a one-off project.

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