Crack in Black Tank

[atrerice]

Last season we discovered a small crack in our black tank, which I repaired with PlastiMend. It stopped the leak and I thought it was going to be a permanent fix. Until a week ago when I de-winterized it. I noticed another crack in the area that was repaired and was dripping. I'm looking at different ways of repairing - Looks like some people have had success with G-Flex 655-8 Epoxy and fiberglass mesh. Another thing I was looking at was PC-7 Epoxy which I have had experience with fixing many things with a lot of success. Does anyone have any recommendations on repairing this crack?

Thanks in advance!

Art

[SteveB]

When I fixed the cracks in the bottom of the black tank in my Jayco, I used black ABS cement and boat cloth. It worked great until the top cracked the next year. Then I just replaced the tank. I think the tank was damaged by something the previous owner dumped into it. Or it was just from being 10 years old.

[Drew_A_]

atrerice wrote:
I'm leaning towards the GFlex epoxy since the first repair I made was with the PlastiMend. Now, that was not with an ABS sheet though. If I use the GFlex, I would embed some fiberglass mesh in it.

I used Plastimend with fiberglass screening on a crack right at the dump pipe outlet and built up the ABS thickness in this area. It has held for several years and I inspect it yearly. No cracks at all.

Did yo use mesh with the Plastimend? I think that using mesh is pretty much mandatory.

[atrerice]

I'm leaning towards the GFlex epoxy since the first repair I made was with the PlastiMend. Now, that was not with an ABS sheet though. If I use the GFlex, I would embed some fiberglass mesh in it.

[time2roll]

atrerice wrote:
That's right a this is a black ABS tank
I do see that Plastimend has a kit that comes with some sheets of ABS. Is that similar to what you did? The spot I will be repairing is right under where the dump pipe connects to the tank.

Yes the sheet was extra from Plasti-Mend. I cut the sheet then used a heat gun to get the curved shape just right before making the repair. All corners rounded etc. Used lots of the adhesive and had a jack ready to gently hold in place. Need to work pretty fast to get it set just right. Next day slathered more on top and especially around the edges of the ABS patch to have everything smooth and stress free.

[wtmtnhiker]

I did about the same as BobsYourUncle as far as tipping the rv etc but I repaired mine with epoxy . I dug the crack out a little so I could get more epoxy into it and it held for a number of years until I traded it in. The surface has to be very clean and dry and I left the epoxy cure for a couple of days with the trailer tipped to the side. Good luck.

[Guy_Roan]

I would go with the West Systems "G-Flex epoxy" if it was mine.

I work with it a lot on repairing plastic, fiberglasss and carbon fiber canoes and kayaks.
It was one of the few epoxies that is made for plastic.

Give West Systems a call and they will walk you through the process

Guy

[atrerice]

That's right a this is a black ABS tank
I do see that Plastimend has a kit that comes with some sheets of ABS. Is that similar to what you did? The spot I will be repairing is right under where the dump pipe connects to the tank.

[time2roll]

Assuming it is black ABS tank I can't imagine anything is better than plasti-mend. Must be some kind of stress point to make it crack again. My leak was at a corner stress point and I used some sheet ABS to strengthen the repair. Holding about ten years now. Good luck with the epoxy or tape.

[atrerice]

That's exactly where the crack is on my tank - right near the dump pipe. Now that you mention it, I wonder if a piece of Eternabond tape would seal it. I've had really good results on the roof and it sounds similar to the tape you describe. One thing I've done on the roof is apply Lexel caulk at the seams of the tape so there would be no chance of it peeling up.

[BobsYourUncle]

I had a fairly large crack in one of mine a few years ago. Noticed stuff dripping underneath....

I was on the road and didn't want to drop the tank, get it fixed and all that. Busy working, no time. I'll fix it properly when I get home.

Being in construction, I always have a great selection of building supplies in my truck tool boxes, including a roll of Bakor Blueskin. This is a peel and stick waterproof membrane used in construction for making things watertight. An extremely sticky tar like adhesive on one side, a smooth flexible 100% waterproof surface on the other. This stuff sticks very firmly to virtually any surface.

I emptied my black tank, then jacked up my TT on the side where the crack was, so any remaining waste in the tank went to the other side. I used some fine sandpaper, thoroughly cleaned the area around the crack, and then liberally wet a rag with acetone and washed the area.

Then I cut a piece of the Blueskin, pulled the backing off and carefully covered the crack, with several inches of the membrane extending past the crack in all directions, thoroughly putting pressure on it to completely stick to the tank.

For good measure, I got out my heat gun (substitute hair dryer here), and got the patch good and warm all over, further working it to the tank with my hand.

My temporary fix until I got home worked so well, that it was still there when I sold my TT about 4 years later. It sealed 100% and never leaked again.

My crack was right close to the dump pipe.