How to patch the gray water tank?

[Funsized]

This used 2720SL is new to us. We realized that the gray water tank is leaking.
Someone had obviously tried to repair it, and a bunch of old caulking came out of the tank.
How do we go about patching it?
Thank you.

 

[Shane826]

https://www.jbtools.com/permatex-84...SKQDCUDzDg8s_g6NHgHM-bGFDz64uLzMaAgowEALw_wcB

Get a couple while you can. Seems to be slim pickings. I have to do the same repair on mine. And then come up with some sort of support strap for the tank. Mine only leaks when it’s pretty full and the belly swells out.

 

[Wavery]

How do we go about patching it?
Thank you.

Can you clean the surface real good then post more pics of the actual crack? Use a degreaser like Simple Green or Orange Cleaner/degreaser. ALL of the road grime will have to be removed. Take pics then sand the area with 60 or 80G sand paper before starting the repair. Sand about 3-4" around the actual crack (do not sand before cleaning).

The repair isn't difficult and I can give you more specific directions if I can see exactly what the crack looks like.

The best repair entails you getting some ABS plumbing pipe or fittings and cutting it up with a power saw of some sort. I used a table saw and saved all of the shavings and slivers of pieces from cutting the ABS. You'll be making your own "glue" (if you will). You will also need some black plastic window screen material as reinforcement and an 8 or 16oz can of ABS cement (any hardware or irrigation store). You will also need a GLASS jar with a lid. I used a 4" diameter jar about 3" tall. Also a 2" wide steel scraper (to apply material) and acetone for ABS prep and clean-up.

You will fill the jar about half full with the ABS shavings, then pour in enough ABS cement to cover the shavings. Mix well with an old butter knife. Let it sit for about 2-3 hours so that it becomes an even consistency of goop. That "goop" is what your tank is made of, plus a chemical (MEK) that melts the ABS. When applied to your (clean) tank surface, the chemical melts it's way into the outer layer of the tank. As the chemical dissipates, it leaves a coat of pure, solidified ABS. You can apply as many coats as you want after allowing 6-8 hours of dry time between coats. I'll explain the window screen application after I see the crack.

That is what you will use for the repair. How you apply and reinforce it will depend on where the actual crack is.

The grooves in the tank are there for expansion. After the repair, you may have to make some support straps for the tank. The repair may be stronger than the original tank but if the original tank material has been stretched (thus thinned) it could break again if not supported.

In the pics attached, my tank outlet was cracked halfway around. All 4 corners were cracked at the top. After the repair, I built an elaborate strap system, shown in pics. You may need to make some sort of support system for yours (to support the weight and prevent further cracking) but your tank is different.

 

[benjburton]

Here's a video I went by and was helpful when I repaired mine that's basically the same thing Wavery describes.

 

[Wavery]

Here's a video I went by and was helpful when I repaired mine that's basically the same thing Wavery describes.

That's a great video. One of the best youtube instruction videos that I've seen.

That's the one that I learned how to do this repair with and the repair is super strong. Especially if you layer it.

 

[Funsized]

Thank you!

Thank you so much for the detailed instructions and video! I did what the RV mechanic we had here told me (JBWeld for plastic) and what an earlier commenter said about adding a support strap.
It only lasted about 24 hours on the first use.
Now I will do what your video describes. I’ll get under there today and get better pictures of the crack. It’s very thin, not a big gap, but long. It’s in the deepest recessed part of the accordion grooves.

 

[Wavery]

Thank you so much for the detailed instructions and video! I did what the RV mechanic we had here told me (JBWeld for plastic) and what an earlier commenter said about adding a support strap.
It only lasted about 24 hours on the first use.
Now I will do what your video describes. I’ll get under there today and get better pictures of the crack. It’s very thin, not a big gap, but long. It’s in the deepest recessed part of the accordion grooves.

That's the worst place for a crack because that groove gets wider as the tank fills. That means that there will be a lot of stress on that repair as that groove expands.

I would drill a 1/4" hole at either end of that crack (like in the video) and proceed with layer the repair. After the repair, you will need to add a support strap under the bottom of the tank to prevent it from expanding as it fills.

This tank is different from yours but the concept is the same. This is my black water tank. I also have a grey water tank exactly like yours.

If you decide to use steel straps, consider getting some fire hose big enough for the strap(s) to fit inside (for chafe protection). If it were me (and I plan to do this on my grey tank), I would use some of that HD styrofoam, that you get in some packaging. to go between the strap and the bottom of the tank. About 1/2" thick should do, to put a little pressure against the bottom. I'm going to adjust the strap so that it just touches the tank bottom. If it's too tight, I'll adjust it out with washers (where is fastens to the cross members) until it just touches.

 

[Shane826]

If you can fill the crack with the tank empty and it doesn’t like [leak?] when half full, add another repair layer with water in the tank so now you’re reinforcing it with the tank swollen. And yes, a support strap is a must. TM now installs them to their new campers.