Gray water holding tank leaks through crack

I've tried to sift through the other threads out there but can't find a definitive and best solution for my gray water holding tank crack.

I just purchased a 2007 2720. It has a crack about 1" long in the center of the tank running iside the indented rib recess. Although, the crack can barely be seen, the water easily comes out as it fills up. As a side note, the level indicators are suck on 3/4 full with the tank empty.

I've read that replacing the tank requires that the trailor be towed back to the factory and the bathtub and tank be rebuilt. This isn't practical.

The bottom of the tank looks like it is vacuum formed ABS. So, the inside of the rib channels would be the thinest material and the center of the unsupported tank would have the maximum flex. I would think cracking at this location would be a common problem.

I've read to drill out the ends of the crack. I'm not sure I can find the end of the crack since it's so hard to see. I've read to use Water Weld 2 part epoxy putty and maybe seal the putty with something else to keep it from seeping.

I've read that the tank is made of ABS plastic and could be patched using ABS cement to bond an ABS patch to the tank. I don't know if there is such a think as an ABS patch that could fit inside the rib recess.

My thinking is to drill a series of holes where I think the crack is and stuff in the epoxy putty using the holes to help anchor it but I'm nervous about causing more tank damage.

What is the preferred way to fix this type of crack? Putty or ABS patch?

Should we be thinking about providing some structural support for the bottom center of the tank so that it doesn't flex up and down to generate more cracks?

-Jeff

[cochise]

The tank is ABS, and you can "weld" it with ABS cement. One way to do this is to clean the outside where the crack appears to be, with ABS primer. Than brush on ABS cement. Better yet At the hardware store where you will pick up the ABS primer and cement, get a roll of fiberglas dry wall tape. The tape should be self-adhesive, and you cut a piece about 2-3 inches longer than the crack. Stick it onto the tank after you have used the primer on the surface. Than just apply 5-6 coats of ABS adhesive over the tape till it is covered. You can apply a piece of clear plastic, like a piece of shopping bag over the patch and hold it in place with painter tape. Next morning you should have a nice weld.

I have done it with several things, the latest was a table saw with a plastic/ABS stand that had broken in two corners. I just added layer after layer of ABS cement and it is just fine. Does it look good? No but it works.

Good luck.

[ShrimpBurrito]

Interesting repair technique, conchise. I hope I never have a need to use it, but if I do, I may just give it a try. What's the purpose of the clear plastic / shopping bag?

Dave

[Wavery]

Originally Posted by cochise

The tank is ABS, and you can "weld" it with ABS cement. One way to do this is to clean the outside where the crack appears to be, with ABS primer. Than brush on ABS cement. Better yet At the hardware store where you will pick up the ABS primer and cement, get a roll of fiberglas dry wall tape. The tape should be self-adhesive, and you cut a piece about 2-3 inches longer than the crack. Stick it onto the tank after you have used the primer on the surface. Than just apply 5-6 coats of ABS adhesive over the tape till it is covered. You can apply a piece of clear plastic, like a piece of shopping bag over the patch and hold it in place with painter tape. Next morning you should have a nice weld.

I have done it with several things, the latest was a table saw with a plastic/ABS stand that had broken in two corners. I just added layer after layer of ABS cement and it is just fine. Does it look good? No but it works.

Good luck.

HMMMMM!! I'd agree with the 1st part of your repair suggestion, not sure about the 2nd. ABS Cement is really not the type of "Cement" that most people think of. It has "Zero" strength or "Build-up" capabilities. If you pour a bunch of ABS cement on the floor, 10 days later you will just have a gooey mess. It won't have any mass. I just don't see where the F/G tape would come in or be helpful.

ABS cement merely chemically melts the surface of the two pieces of ABS that are to be adhered to each other. As the two treated pieces re-harden, they become one piece. Just like welding metal. The difference with metal is that you are using metal welding rod that can be built-up to add strength. ABS just doesn't work like that because it is a chemical reaction on the surface (only) of the ABS.

You can buy ABS in thin sheets. Sanding each layer with 80-100g sandpaper will help add to adhesion. It can be heated and molded to fit into the recess that you describe (or any other shape). I would suggest building up several layers. Applying ABS to both surfaces that are to be bonded (the tank and 1st patch). Let that patch dry. Sand or grind off any edges and smooth out the edges. Then make patch #2 a little larger and bond it to patch 1 and the tank (maybe 1/2" beyond the original patch). You could do 4 or 5 layers and buildup quite a bit of strength over a good sized area. Round patches are best but NO square or sharp corners on whatever shape you use.

I'm not sure if this will work for ABS or not, but it might be worth looking into: http://www.permatex.com/products/Aut...Repair_Kit.htm They claim it works for a crack up to 4 inches in length.

A web search for "ABS repair kit" also yields some responses that may work.

Finally, ABS can be plastic-welded, although that might be a bit much if you haven't done that before. Our household uses a plastic welder and the appropriate welding rods (ABS plastic for this use). They are tricky to use, and I'm definitely not great at using it (I'd be more likely to try a patch than to weld it personally).

I remember this ABS repair from another well known hard sided popup only back then it was on the sunny side of the camper. Same principals though. Look at this link http://www.apachepopups.net/SMF/index.php?topic=6645.0 and fourth post down. These guys have been making repair patches using MEK and scrap ABS for years. The latest incarnation looks like you can stop at Lowe's for the MEK and secure some ABS from kids' Legos. Hope this helps

Looking at the suggestions:

The build up with ABS cement, fiberglass, and shopping bag is a little strange chemically. Fiberglass will add structure. Shopping bags are made of polyethylene which is thin version of the same material used in buckets. Neither should react with ABS cement but hard to argue with proven success. I hadn't thought about cleaning with ABS primer but that is a great idea.

The whole Permatex site looks like a good resource for a lot of patch and repair kits. The one for fixing tanks uses a two part epoxy with fiberglass reinforcement. That would work but doesn't take advantage of of the ABS material in the tank.

The ABS welding could work, although this is just a micro crack that doesn't have a gap to be filled.

Creating a paste with MEK (Methyl Ethyl Ketone) and legos is very clever. Legos are made from ABS and MEK disolves just about any kind of plastic. It's also a good paint remover. This type of paste would have the same color as the legos, a real advantage for a cosmetic situation involving ABS repair.

Putting all this together...
I'm thinking to clean the area with ABS primer, make a black paste using ABS cement and ABS pipe shavings, reinforce with fiberglass mesh (drywall tape), and layering it up to cover the fiberglass. I would want to try this on a scrap pieces of ABS before trying on the tank. I'll get back to the forum on how this works.

[Wavery]

Originally Posted by maxandkona

Looking at the suggestions:

The build up with ABS cement, fiberglass, and shopping bag is a little strange chemically. Fiberglass will add structure. Shopping bags are made of polyethylene which is thin version of the same material used in buckets. Neither should react with ABS cement but hard to argue with proven success. I hadn't thought about cleaning with ABS primer but that is a great idea.

The whole Permatex site looks like a good resource for a lot of patch and repair kits. The one for fixing tanks uses a two part epoxy with fiberglass reinforcement. That would work but doesn't take advantage of of the ABS material in the tank.

The ABS welding could work, although this is just a micro crack that doesn't have a gap to be filled.

Creating a paste with MEK (Methyl Ethyl Ketone) and legos is very clever. Legos are made from ABS and MEK disolves just about any kind of plastic. It's also a good paint remover. This type of paste would have the same color as the legos, a real advantage for a cosmetic situation involving ABS repair.

Putting all this together...
I'm thinking to clean the area with ABS primer, make a black paste using ABS cement and ABS pipe shavings, reinforce with fiberglass mesh (drywall tape), and layering it up to cover the fiberglass. I would want to try this on a scrap pieces of ABS before trying on the tank. I'll get back to the forum on how this works.

I forgot about using ABS shavings. I've heard of that before. You can make your own with an ABS pipe and a file or hacksaw.

ABS cement is, basically, MEK. Practice is a good idea. Working time is the issue, you would have to be very quick and don't forget to put a coat of ABS cement on the tank before applying the goo mixture.

I still don't see where the F/G tape comes in. It won't stick to the tank and the cement won't work on it. If your thought is, "Holding the muck in place", I don't think that should be and issue. Adhesion should only take a few seconds, as the 2 surfaces make contact. Pressing the mixture tightly against the tank with a trowel for a few seconds should do the trick. It shouldn't stick to the trowel.

IMO, if you use the F/G tape, it could complicate any further repairs, in the unlikely event that the patch leaks in the future. If you fill the concave area with the goo that you've created, it might be a good idea to try to level the surface to the rest of the tank. That would facilitate an easier surface to make any future patches.

Originally Posted by maxandkona

I've read to drill out the ends of the crack. I'm not sure I can find the end of the crack since it's so hard to see. I've read to use Water Weld 2 part epoxy putty and maybe seal the putty with something else to keep it from seeping.

Along with all of the excellent advice on how to fix the problem, if it were me I would still drill a hole at the end of the crack to prevent further stress. You don't have to use a very big bit.....maybe 3/16th or so.

[cochise]

Originally Posted by ShrimpBurrito

Interesting repair technique, conchise. I hope I never have a need to use it, but if I do, I may just give it a try. What's the purpose of the clear plastic / shopping bag?

Dave

Just to smooth it out and prevent dripping while is cures. And the tape is to fortify it. It work, I did it on a rain water reservoir and also on watering can that had cracked.