Carl November 2, 2007 Share November 2, 2007 (edited) I'd like to drill my 75 for a closed loop and for skimming. How many holes are too many? when do I start worrying about the integrity of the glass? Here is what I'm thinking - all holes in back glass of tank. - 2, 1.5 inch holes near the top to skim, then feed into the sump (return to tank over top) - 2, 1 inch holes 1/2 way down the back, to return from CL pump - 1, 2 inch hole to drain out of tank, into CL pump Would drilling the holes near the middle of the glass cause more stress than towards the sides or the edges? 'preciate your input. -Carl Edited November 2, 2007 by Carl Link to comment Share on other sites More sharing options...
Carl November 2, 2007 Author Share November 2, 2007 (edited) I could re-phrase the question... Who has the most drilled holes in a 75 gallon glass tank...and the tank is still holding water! Edited November 2, 2007 by Carl Link to comment Share on other sites More sharing options...
phisigs79 November 2, 2007 Share November 2, 2007 Check with Steveoutlaw i thought i remember him having alot of holes drilled in his tank Link to comment Share on other sites More sharing options...
yauger November 2, 2007 Share November 2, 2007 I don't know if that many holes in the bottom of a glass tank would compromise the stability. I have that many in my acrylic tank and NAGA has even warned me about future leaks that I might endure... just a thought but acrylic is much stronger than glass so you might have an issue... have you thought about placing some of those holes on the back wall? Link to comment Share on other sites More sharing options...
Carl November 2, 2007 Author Share November 2, 2007 I don't know if that many holes in the bottom of a glass tank would compromise the stability. I have that many in my acrylic tank and NAGA has even warned me about future leaks that I might endure... just a thought but acrylic is much stronger than glass so you might have an issue... have you thought about placing some of those holes on the back wall? Yes, all of the holes I'm considering are in the back wall of the tank, not the bottom. I'm also thinking that all the holes will be at least 1/2 way up from the bottom, so worst case scenario, when Murphy hits, I'd only lose 1/2 the water onto my floor, not all of it. And if I had to replace a bulkhead, I'd have to empty 1/2 the tank, not all of it. Link to comment Share on other sites More sharing options...
phisigs79 November 2, 2007 Share November 2, 2007 Or the whole back could blow out Link to comment Share on other sites More sharing options...
yauger November 2, 2007 Share November 2, 2007 Or the whole back could blow out that would really be bad... Link to comment Share on other sites More sharing options...
Carl November 2, 2007 Author Share November 2, 2007 Or the whole back could blow out That's what I'm worried about... I know folks drill holes...and I presume there are a bunch of 75's out there...so curious what folks have done...and not have a blown-out tank. Steve O - how many holes did you drill in the back of yours? Was it glass? Link to comment Share on other sites More sharing options...
Rascal November 2, 2007 Share November 2, 2007 Would drilling the holes near the middle of the glass cause more stress than towards the sides or the edges? Yes, but too close to the edges can be bad too. I remember reading the distance from any edge should be at least equal to the diameter of the hole. I also think drilling towards the bottom causes more stess than towards the top, since the water pressure is greater. acrylic is much stronger than glass so you might have an issue... Acrylic is stronger but bends more. If it bends too much it will start to pull at the seams, possibly causing a leak. Glass isn't as strong but it is harder - so it won't bend as far b/f it breaks. If the glass is weakened to the point it starts to crack it won't be a matter of just losing water down to the bulkhead. You probably don't have anything to worry about with the number and amount of holes you have planned, but if you are concerned there might be a couple of things you can do. One is to add some glass bracing to shore up the side of the tank that has a lot of holes in it. For example, get a 1/2" piece of glass 48" x 4" and silicone it across the back of the tank in between the top and bottom set of holes. I don't know for sure if this will work, so put this in the "seems like a good idea to me" department. Another option is to run your CL returns over the top of the tank instead of having them come through the glass. Link to comment Share on other sites More sharing options...
lletellier November 2, 2007 Share November 2, 2007 have you checked to make sure the glass isn't tempered?? I was told that most aga tanks above 50 gal are tempered.. don't know if that applies to other types of tanks. Link to comment Share on other sites More sharing options...
Carl November 5, 2007 Author Share November 5, 2007 I believe the bottom is tempered, and the sides not tempered...so I think I"m good there. The additional glass bracing sounds like a logical idea...alhtough not sure if silicone alone would actually be strong enough without flexing to make a difference. And running the CL over the top is what I'd fall back to...drill the two top "skimming holes", and one feed to the pump on the CL, then put all four returns from the CL pump up and over the top of the tank... But I would be so excited to actually not see any pipes at all!!! Link to comment Share on other sites More sharing options...
Rascal November 5, 2007 Share November 5, 2007 The additional glass bracing sounds like a logical idea...alhtough not sure if silicone alone would actually be strong enough without flexing to make a difference. The reason I thought it would be a good idea is that silicone is what holds all glass tanks together. Silicone alone. Try to take one apart some time and you'll gain new respect for just how strong it is. Peals right off everything else, but stick glass to glass and you will not be able to pull it apart. Link to comment Share on other sites More sharing options...
Carl November 5, 2007 Author Share November 5, 2007 (edited) I am still VERY curious how many holes have folks successfully put in the back glass of their 75 glass tank? one hole? two? five? more? -Carl Edited November 5, 2007 by Carl Link to comment Share on other sites More sharing options...
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