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Old 08-12-2019, 07:59 PM   #1
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Need adhesive for a crack in black tank.

I have a small, about 1" crack in my black tank. It's way up high so it's only a problem if I let the tank get to full. It's in a difficult location, right on the trailing end corner where the tank sits on a piece of angle iron but it's accessible. I tried some of the "seen on TV" flex seal (I sawed my boat in half!) and that didn't hold worth a ding dang (being polite). I also tried some ABS glue that seemed to hold at the time but later on it failed. What I did was clean the surface of the crack then apply the glue. After 2 days of curing I filled the black tank with water and let it sit overnight to see if I had any leaks. The ABS didn't leak at the time but a couple of months later when I didn't monitor my black tank levels adequately it started to drip. I have the corrugated metal bottom panels on my 2008 Cardinal 5th wheel so it's a pain in the butt to access the tank. I want to fix it one more time and need advice as to what kind of adhesive will stick to these Elkhart Plastics tanks? I got a tube of 3M 5200 marine adhesive/sealant and unless I hear differently that's what I'm going to try next. This time I'll cut a groove along the crack with my Dremal so I can get adhesive inside the tank and along the outside instead of just applying something on the outside of the crack. I've already stop drilled the crack. I'd like to apply a patch over the crack and screw it to the tank but it's pretty thin and I don't think a screw would hold. Anyone got something I haven't thought of yet? Randy.

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Old 08-12-2019, 08:17 PM   #2
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I used Liquid Rubber on my black tank and it lasted for 5 years before I sold the trailer. This stuff is used for flat rubber roof repair, when it cures it turns into solid rubber.


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Old 08-12-2019, 08:45 PM   #3
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Proper way would be to have it plastic welded.
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Old 08-12-2019, 08:56 PM   #4
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Worth a shot. I have used it on water tanks (stationary) but I do not know how well it will travel. . Use the card of ABS they provide as a patch.
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Old 08-13-2019, 03:22 AM   #5
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Use flex seal tape. Great stuff.
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Old 08-13-2019, 10:55 AM   #6
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Thanks for the tips! I tried to find someone local who could plastic weld the crack but I think I'd have to drop the tank for access. If I do drop the tank I'll probably replace it.
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Old 08-13-2019, 11:06 AM   #7
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Donít if you can get to it but Iíd drill a small hole at the ends of the crack to help stop it from continuing. Then Iíd use a heavy duty rubberized tape over the crack.
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Old 08-13-2019, 11:06 AM   #8
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I'd try Eternabond tape.
It has stuck to everything I've touched it to. (make sure you apply good pressure for adherence)
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Old 08-13-2019, 11:12 AM   #9
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Wonder how well 'eternabond' tape would work on that situation? That's assuming of course you could get good access to the crack.
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Old 08-13-2019, 11:37 AM   #10
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I would clean around crack and then use a coarse sandpaper and sand couple inches each side. Clean with acetone and then apply a good exterior silicone caulking over the entire area.

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