Fixing crack on 330g some advice

[Zylumn]

I purchased the 330g tank from Nate(great guys BTW) that was dropped. 84x30x30 When I got it home I found it to be in far better shape than I could have hoped. I was told it would probably need front and back glass and I purchased it with that expectation.
--Front glass---
There is some chips off the front bottom piece of glass but it will not affect the glass integrity as it is not cracked and an additional 3" wide by 1/2" was put in all away around the bottom inside of the tank. I understand why Nate would consider it replaced as it is not perfect and in my case I want it in a in-wall and it will not be seen. That said: I saved replacing front glass ($300) and huge hours of labor.
--Back Glass--
This one received some damage but I think I can fix it without replacing the back panel of glass. The crack is contained in a circular fashion in the left rear overflow. Now the key points here is the side and the bottom pieces of glass received 0 damage and the crack has circled in on itself with no potential lines shooting out to the rest of the back panel. Now as it is contained within the overflow there should be less pressure on that crack. I plan to add a piece of glass (the width of the inside overflow, 1/2" thick) with silicone on the bottom, side,back, and overflow piece of glass. Effectively concealing, and taking all pressure off the crack. This would save me $300 and 50, 60 hours of labor.

Heres a pic
http://s168.photobucket.com/albums/u173/zylumn/?action=view&current=cracked-corner.jpg

I am interested in experienced criticism and advice. Thanks for looking.

Kevin

[Chin_Lee]

Kevin
Will you or do you have the means to remove everything from your tank to fix it in the future if it does start leaking? I think thats a critical back up plan that needs to be in place before you make the decision.

Having said that, I think its salvagable without removing the entire piece. My only big concern with the crack is that its at the bottom which means if the crack spreads, it will spread from the bottom meaning any leaks will drain the entire tank over time.

My understanding of the tank structure is that it has a eurobracing at the top and the bottom - is that correct?
If thats the case, its the same tank manufacturer as mine and I have to say the tank is quite strong structurally. The way I see it, the crack will spread if there is any bowing in the glass. I would put 1/2" piece of glass that is as wide and big as possible and sandwich the cracked piece and the inside of the overflow entirely - kinda like overkilling on eurobracing the inside of the overflow as well as the outside part.
Another consideration is make sure your stand and tank is completely and immaculately level. Deviations in the levelling will increase stress point on your tank and in your case with a 84" long tank, this may cause the crack to spread.
If it helps, I can put a straight edge onto my tank to see if there is any bow at all ; my tank is a 300g cube thats 30" high. Unfortunately its only 1/2 the length of your and slight bowing may be even be present with such a your long tank. I will look into it tonight when the lights comes on.

[Nate]

As I said in the first place, I would not feel confident using that panel of glass. (the back one).

And I know that this is a completely seperate type of scenario and type of glass, but glass is very unpredictable, think about your windshield when you take a rock, it hits, nothing really happens, a small mark, glass cools down, heats up, and then you have a crack all the way through.

That is why I was not going to use the tank. I actually am in the process of setting up a 600 gallon tank, and could have used this as a sump, and chose not to. I have no trust in glass that has taken that kind of abuse, and in the end, it might just not be worth it.

That being said, I hope it all works out for ya.

NAte

[Myka]

Personally, I wouldn't take the risk of buying a cracked tank not even if it was free. There is likely to be thousands of dollars of livestock in that tank one day, and if it fails all is gone, and the risk is too great for me. Good luck.

[Zylumn]

Thanks Cin_Lee for your comments.


I think thats a critical back up plan that needs to be in place before you make the decision.
Agreed. I do plan on running the tank for at least 6 months in my garage with fresh water before I place it in the house.

Having said that, I think its salvagable without removing the entire piece. My only big concern with the crack is that its at the bottom which means if the crack spreads, it will spread from the bottom meaning any leaks will drain the entire tank over time.

My understanding of the tank structure is that it has a eurobracing at the top and the bottom - is that correct?

Correct Eurobracing bottom and Double top and the tank is very strong structurally.

The way I see it, the crack will spread if there is any bowing in the glass. I would put 1/2" piece of glass that is as wide and big as possible and sandwich the cracked piece and the inside of the overflow entirely - kinda like overkilling on eurobracing the inside of the overflow as well as the outside part.

Yes hadn't thought of that

Another consideration is make sure your stand and tank is completely and immaculately level. Deviations in the levelling will increase stress point on your tank and in your case with a 84" long tank, this may cause the crack to spread.
If it helps, I can put a straight edge onto my tank to see if there is any bow at all ; my tank is a 300g cube thats 30" high. Unfortunately its only 1/2 the length of your and slight bowing may be even be present with such a your long tank.

The tank also has a 1 foot wide center brace on top of the Double thick top Euro-bracing.
I will look into it tonight when the lights comes on.

Thank you Chin

Hey Nate
Thanks for chipping in (bad pun)
Anyways just to elaborate on the windshield demo, I've had a crack in my windshield from a rock in the top corner and the crack continued until it found the side edge. Now that was 2 years and because there is a start and a finish to the crack it will not spread, as with the tank crack it starts and finishes. Now I do not feel that my windshield is near as strong as it was brand new. But I also feel if I took a piece of windshield glass and formed it to cover 1/4 of my w/shield and properly securing it into place I would feel that cracked area would now be stronger than brand new.
Nate you have seen the tank and I Do appreciate your expertise so please continue to tag along.
Thanks

Myka
Thank you for your valued opinion. This thread is not about whether I should purchase a cracked tank (since that is in the past) but how to fix it utilizing experience and education this valuable site exhibits.
Thanks again



Chin a question for you. I do have a piece of 5' x 4' x 3/8" glass that I could have cut to strengthen the overflow and run along the back of the tank nearly to the opposite overflow. Now I would have two 1/2" pieces of glass sandwiching the cracked area. Anything you would add to that??
Kevin

[Myka]

Myka
Thank you for your valued opinion. This thread is not about whether I should purchase a cracked tank (since that is in the past) but how to fix it utilizing experience and education this valuable site exhibits.
Thanks again

I understand Kevin. I am just concerned, and am urging you to reconsider trying to fix this tank, but I won't comment anymore. :)

[Nate]

windshields dont have 300 gallons of water pressure on them causing them to bow either. I think I would bemuch more confident in the tank if it had a new back panel...

Nate

[Snappy]

http://i168.photobucket.com/albums/u173/zylumn/cracked-corner.jpg
I would suggest you error on the side of caution. I think you should just cut through the sylicone and have new pieces cut and re-installed. I'd hate to see it come back to haunt you later.

[Black Phantom]

I'm not sure that your overflow will have less pressure as the pressure at a given depth is independent of direction -- it is the same in all directions.
I have a large tank myself and just knowing how much time and effort went into the tank as far as livestock, corals, liverock etc, I would replace any glass that might have had it's integrity compromised. Everyone here has seen what a couple of spilled gallons can do let alone hundreds. Your investment will end up being in the thousands of dollars by the time your done. Don't cheap out just to save a couple of bucks

[Zylumn]

I have been doing a lot of thinking about fixing this 330g and thought I would just see how much a new back piece would cost. So I called Mitch at Bow Valley Aquariums and he said it was a very slow day due to the cold and if I wanted the back today he would give me a good deal. While I was already there I picked up a front for my 78g cube. Now I just have to wait for the weather to warm up and I have some cutting to do. Mitch at Bow Valley was very helpful and informative. He told me the skinny on cutting the back panel off and how to properly silicone the back piece on and was able to get me some silicone and tape. Thanks all for your input and I will keep everyone informed on my progress.

Kevin

[Skimmerking]

Well I know when I took my 280 gal apart it was 5/8" glass and with 2 people its alot easier wit 2 . when I was stripping the silicone off I had my self actually pulling hard on the glass and the other guy was cutting it it actually went really smooth too. from total time it was like 45-60 mins from the time we started to the time we ended..


good luck,

[Chin_Lee]

Well I know when I took my 280 gal apart it was 5/8" glass and with 2 people its alot easier wit 2 . when I was stripping the silicone off I had my self actually pulling hard on the glass and the other guy was cutting it it actually went really smooth too. from total time it was like 45-60 mins from the time we started to the time we ended..


good luck,

When I did have to cut glass off, an expanding clamp helped alot along with this strategy of pulling and cutting.