help me fix/reseal my acrylic sump

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cvermeulen

Jack Dempsey
MFK Member
Jun 4, 2007
1,876
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Los Osos, CA
OK, looking for someone who knows a lot about acrylic construction, because I'm starting to get pretty frustrated.

The background: I built a lovely (looking) acrylic wet/dry a few months back, and put it into service. For all the seams I used methylene chloride to solvent weld them. About a month afte rI put it into service, 2 seam decided to let go. So I put it in the shop, and scratched my head for a while. I read somewhere that methylene chloride seams may fail in aquaria after some service life. Soooo, I put a reinforcing strip along the inside of EVERY seam, and fastened it there with weld-on #16 (the gooey, gap-filling acrylic cement stuff.) After that cured, just as extra insurance, I ran silicone beads down all the seams to act as a sealant in the event that my acrylic seams were not perfect.

The problem: One month later, the thing has developed another leak, at another seam. The seams I repaired are fine (for now) but another corner seam has developed a slow(ish) leak, despite the reinforcing strip, and the silicone. Now, I haven't investigated the seam very thoroughly yet to determine what exactly went wrong, but seriously, WTF!!. Can anyone recommend a sealant type material, that will be fish safe, that I can put a bead in the corners with? The silicone seems to stick to the acrylic pretty well, and I'm not sure what's happened at the leaky spot... I'd like to find something like an even thicker weld-on product, that I can run down all the seams, but that will harden to a solid joint, forming a fillet in the corner.

The tank is running on an FX5 right now. Part of me is tempted to just get another FX5 and call it done, but the W/D combined with a RUGF at 3000gph is really tough to compete with in a canister. Plus the tank has built in overflows, etc... be a bit of a waste not to use them.

Help!
 
Somebody's gotta have a suggestion... right now my idea is just to strip and re-seal the seams like I would an aquarium, but I remain leery about the long term reliability of this thing.
 
Since you already have the weld-on, stick with it. Strip out the silicone and just use the weld on to form corner beads/seals. Plan on this being a long project because you can't rush it; you will need to do one joint at a time. Prop the cleaned sump on an edge and pour a little weld-on into a seam from corner to corner. Wait for it to firm up before moving on to the next seam. You can do multiple seams if they are parallel and on the same side. You will want to be creative and practice making nice looking joints if this is to be a show piece. You can use a natural fiber paint brush to spread the glue; a synthetic brush may melt. After you are done with all of the seams, let it cure for at least two days in a well ventilated area. Test the seams for hardness and do not put it into service until the last seams are hard on the inside.
 
Thanks for the recommendations... I was sorta thinking along those lines, but I was hoping to find something with a higher solids content than weld on #16. It's designed to fill gaps, but it's still pretty runny. I guess maybe that's a good thing as it might run into any gaps in the seam.

Now of course I'm kicking myself HARD for putting silicone in there, because it's a biiiiiiiiitch to get out. So far I've used a chisel to scrape the worst of it off and then contractors solvent to soften what's left and scrub it off with a wire brush. (yeah, I know it's going to look like ass by the time I'm done... i've resigned myself to having an ugly sump by this point.) Anyone got a better (preferably chemical) way to remove silicone? There's gotta be something that will eat it.
 
Gasoline will break down silicone, but I do not know the required contact time. Acrylic is also porous on the atomic scale and I do not know how gas will absorb & release during evaporation. You can test it with a piece of scrap if you have some. Soak it and then let it dry for a few days. When the smell is gone, that will tell you how long the sump will have to vent off the absorbed gas.
 
Yeah I'd rather not soak my sump in gasoline... it would probably help, but like you said, god only knows how long it would take to gas off, or even how it might react with the acrylic. This contractors solvent stuff does it slowly, and washes off. I'm going to see if I can get a nicely sized nylon or steel wire wheel for my D/A grinder to battle the bulk of the silicone. Hopefully I can get away without damaging the acrylic too badly.
 
yeah no kidding. Sump is like 40gal :p Nevermind the mess when it leaked on my floor. And that whole fire thing.

Chompers is an Engineer (or almost, I forget if he's finished school yet) though, and we tend to generate ideas first, and think of reasons they might not work second. ;) Any input is valuable.
 
I always use a cryoacryllic glue (superglue) for that kind of repair because it can pepetrate tiny openings in seams and bonds to ALL meterials. It's non-toxic once allowed to dry.
 
Do you have a specific product name? I'd be hesitant to use "krazy glue"... there are a lot of permutations of cyanoacrylate based adhesives... I hadn't thought of CA though, that's a good suggestion. I'd still like something thick to make beads in the seams as well though. I briefly considered ARL's goop and tilt method, but I'm not sure how well GOOP bonds to acrylic.
 
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