fixing glass tank bottom
 

I got a 180 gallon tank with a cracked bottom that I would like to use as a sump and am looking for way to fix it. I was thinking about silicone with apeice of glass on the bottom to seal it. Iam open to sugestions

THanhs Bruce

Do you know what caused the tank the to crack? If the bottom is not flat a fix might now work very well.

You should be able to silicone a piece of glass over the crack and use the tank as a sump without any problems

Kim

ummm from experience putting a piece of glass over an exsisting crack is only asking for trouble, your just putting a band aid on something that will eventually crack again. If you have a tank builder local to you you can get a whole new bottom pane for relatively cheap. I got a 48x24 1/2" thick piece for under $80 from a local tank builder.

If it was me I'd sleep much better at night with a new piece instead of a piece of glass over it.

As far as replacing, you'll have to remove the old bottom pane and then put a new piece back on. Make sure there is no leftover silicone otherwise you'll be sorry.

If you really are wanting to use a piece to just silicone in over the crack make sure you cover the entire crack, if the crack is going through the seam your going to want to just replace the entire bottom pane.

The tank is cracked at one end all the way across and I will put a piece of glass that will extend a foot past the crack

its possible it could further crack at some point but if your going that route that should do it, I'd put some bracing underneath as well to keep further stress cracking.

[QUOTE][i]<a href=showthread.php?s=&postid=11521622#post11521622 target=_blank>Originally posted</a> by corivus [/i]
[B]ummm from experience putting a piece of glass over an exsisting crack is only asking for trouble, your just putting a band aid on something that will eventually crack again. If you have a tank builder local to you you can get a whole new bottom pane for relatively cheap. I got a 48x24 1/2" thick piece for under $80 from a local tank builder.

If it was me I'd sleep much better at night with a new piece instead of a piece of glass over it.

As far as replacing, you'll have to remove the old bottom pane and then put a new piece back on. Make sure there is no leftover silicone otherwise you'll be sorry.

If you really are wanting to use a piece to just silicone in over the crack make sure you cover the entire crack, if the crack is going through the seam your going to want to just replace the entire bottom pane. [/B][/QUOTE]

All perfect good points. with a tank as big as a 180, you really shouldn't push your luck for the sake of saving work, and a few bucks. I had the same failed experience of trying to patch a large crack in a 125. You'll never be able to apply uniform pressure over that large an area.

However I was corrected on the issue of new silicone bonding to previously cured silicone. I was under the same impression. I was corrected by a Dow chemical engineer in another thread. Make sure the cured silicone is extra clean and use Dow999. That's probably what's used in jumbo tanks anyway.

Here is a couple of adhesive to look at; Black Dow Corning 999-A silicone, GE RTV108, SCS1200 and Dow Corning V2 sealant!!!

I also use Digesil Gel Silicone Stipper for vertical applications for removing old silicone!!!

Maybe if you drilled the ends of the crack before patching it would hold up better?

I had a small chip on a corner (1" long) on my 50g, here what I did:

Go to a local glass shop, ask for a 1/4 or 3/8" thick glass that will cover ALL the bottom inside your tank. Ask them to remove some of the corner so it could fit with your existing silicone.

What I did is take a tube of Silicone and put all around your existing edge inside on the bottom and then put all the rest of the tube all around the tank's bottom. put the glass on the bottom than make the bottom seam all around the edge with the silicone.

Adding the silicone between both glass sheet will reinforce it.

I think I am just going replace the whole bottom panel. Does any body know how the bottom panel on a all glass tank would comeout. Do you have to take off the bottom trim and how

[QUOTE][i]<a href=showthread.php?s=&postid=11525712#post11525712 target=_blank>Originally posted</a> by brucem [/i]
[B]I think I am just going replace the whole bottom panel. Does any body know how the bottom panel on a all glass tank would comeout. Do you have to take off the bottom trim and how [/B][/QUOTE]

There's no really "easy" way to remove the bottom trim. If you have a knife with a very flexible blade like a filleting knife, you can run it between the trim and the glass on all sides until the silicone bead between them is completely cut through. The less laborious way is to simply cut the trim in a small area with side cutters, and just prying it off. You can buy replacement trim for any stock AGA tank directly from them. AGA changed their name, but if you search AGA you'll get to them easily. hth

fwiw, I think you made the right choice.

I got the botton off with a 2x4 and a rubber hammer

You were lucky. sometimes the trim has so much silicone in there, you want to use a ball peen hammer instead, lol!

yup the hammer method is what I used as well