Metaframe Slate-Bottom Tank - Dow Corning 795

Okay, so I did a search here on how to re-seal Metaframe tanks that have a slate bottom and saw Oddball's response on an older topic saying that some people he knew had success using Dow Corning's 795 Building Sealant.

I'm about to begin this very same project on a 100 gallon Metalframe tank that has a catastrophic leak on one end about 3/4 of the way up the side wall. I will be cutting away all current sealant, then re-sealing the entire tank at one time. While researching this particular product though, it specifically says something that worries me:

"Dow Corning 795 Silicone Building Sealant should not be used on surfaces that are continually immersed in water."

Any update on this product? Is this something I should worry about? Is there another product that would be more suitable? Thanks in advance!

Also, one more thing on this before I begin trying to reseal this beast: do I need to worry about this side foam?



I believe this is simply there to cushion the glass against the metal. If the inside is fully sealed and my thinking is correct, it wouldn't play a part in keeping the water inside the tank at all. I'm just trying to avoid having to completely disassemble this tank as I've heard that that can be a nightmare with these older tanks and usually results in at least a few panes being broken.

As far as the sealant is concerned, unless I hear otherwise from this community, I think I'll go with the Dow Corning 732 instead of the 795. Even though it still says not for use on submerged materials, at least there are more people here who've used it successfully and it's food safe.

Well, that explains a lot. Thank you!

I've been examining that "foam" and comparing it with pics of other metal framed tanks. There's no way that can be the old sealant. It would have had to have been over 1/2" thick standing up along every surface of glass and shoving it away from the metal. That's not the behavior of tar. Tar would coat and get between the glass and metal, but it wouldn't be over 1/2" thick and be consistant like that along the whole tank. In all other pics of these old tanks (both before and after refurbishing) the tar is there, but not near that thick, nor does it resemble an old rubber seal like this does.

I think someone tried to rebuild this tank in the past using rubber seals similar to what you see in weatherproofing windows and doors in old campers. Either way though, it means I'll have to try to tear the whole thing down instead of just re-sealing it. Aw well, it'll look better in the end anyway.

Now let's hope I can manage to remove the glass and slate without breaking any.

Thanks, deeda. I'll keep you all updated. My first step is to polish the metal as it'll be much easier to do before I get the glass and slate out. After that, I'll disassemble it and fix whatever needs fixing. Given that DC 795 has been used with good success in the past, I'll continue to use it as the sealant as suggested by Oddball.

I won't be able to get fully started on this for a few days though as I have relatives coming into town.