Repairing An Acrylic Crack - Any Chance?

[wahoowa]

So today I picked up a 75 gallon acrylic for a steal of a price. The tank hasn't been setup in 7 years and before that it had been up for about 6. The guy didn't guarantee that the tank didn't have any leaks, though he said there were none when he tore it down. Tonight I did a practice fill and found that there is a substantial leak between the back panel and the right side of the tank. I would say the leak is about 8" long. Is there ANY chance that this could be repaired? I am not really into paying $450 for a brand new one. If it could be repaired, how would I go about doing it?

 

[cranberry]

Get some good acrylic cement like weld on. You could even cememnt a 90 degree acrylic brace in place if it wouldn't be viewable.

 

[stanlalee]

acrylic weld structurally should make it as stong as new. a bad job will show though

 

[meowzer]

I used something called waterweld on my sump...worked great...

 

[wahoowa]

Awesome guys.
Here was what I was thinking in terms of the repair.
#1. Cleaning everything with alcohol.
#2. Clamping everything together super tight.
#3. Apply the Weld on (or w/e I go with) to the corner area on the inside AND outside of the tank.
#4. MAYBE put a couple braces in the corner that is having problems
#5. Fill it up and hope for the best.
If there is anything that I can do to make this work or to do a better job, please post!

 

[gypsana]

The thing about Weld-on is that is is not an adhesive per say. It joins the acrylic by melting the two pieces together. If the leak is from a crack or a bad joint just applying Weld-on will not fix it at all. The only sure fire way of making sure your tank will be leak proof is to get a strip of 1/8" acrylic cut big enough to cover the trouble area and use the Weld-on to adhere that. I know that it may not look the best but from my experience this is the only way I would do it myself. If you are finding one leak like that I may be a little scared about the possibility of future leaks. I would look into a used glass tank personally, they are easier to repair.

 

[wahoowa]

I was worried about other leaks too, but if I do one new "brace", I might as well rebrace the whole thing. I'm not worried about the way it looks, my live rock will cover the majority of it.

 

[mkroher]

You can get a used 75gal glass tank on CL for <$100.

 

[jackri]

I totally agree with Gypsana. Cut the 1/8" inch strip -- barely visible and use weldon #4 and it will melt it all together. This is how I fixed my sump tank leak and just used some extra in my frag tank for self assurance and I never notice the strips.
More info on it can be found at:
https://forums.saltwaterfish.com/t/350650/frag-tank-stand-build

 

[scsinet]

IMO it depends on how thick the acrylic is.
If it's 1/4 or 3/8" acrylic, and the "crack" is rather a busted joint (which it what it sounds like here), it may be fixable by simply using a needle applicator to apply weldon to the seam, which should draw in the cement with capillary action, then clamp it down tight to "mush" the seam together and drive out bubbles.
That said, given that it's the back of the tank, I would certainly say that adding a corner block as others have suggested here couldn't hurt and shouldn't significantly detract from the appearance of the tank.
DO NOT use a surface cement such as model cement, Weldon #16, goop, etc. It will not achieve proper structural strength and will fail again, guaranteed. It's okay to use these in addition to a weld, but not by themselves.
The last thing you want is the seam to fail again once the tank is set up, so whatever you do, you need to be 100&#37; confident in the repair you've done.

 

[wahoowa]

It's definitely a busted joint. I checked it out more today (too P'd to really investigate last night) and its the back panel coming off of the side or vise versa. What I think I'm going to do it use weldon #4 on the broken seam itself first, let that dry, and then do a brace over that for an added layer of protection. If this seems to work well, I'll rebrace the other joints as well.
Only question is, how much Weldon #4 will I need? Will a pint do a 75 gallon tank? I'll also pick up an applicator bottle and needle tip. Anything else I'm forgetting?

 

[scsinet]

Yeah, a one pint can will certainly do it, with lots left over. A little of this stuff goes a long way.
You should consider getting two applicators, they are throwaway items that often clog.
Keep in mind that you cannot "re-seal" joints that are already welded. It will do you no good to re-apply the stuff to seams that are still in good shape.