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Discussion Starter · #1 ·
Hello all! I have an older fifth wheel (2004) with a crack in the black tank, we took off the metal sheeting and we can see it, maybe 5"-6" long or so, and the water is coming through it pretty strong. It's in the side of the tank. The only dealership we can get to doesn't handle hazmat and won't replace it for us. At the moment we've exhausted every avenue and our only option is to try to patch it ourselves. When we asked about what we should use to patch it, the dealer said the tank is made of "some kind of molded plastic." That was all the advice they would give. The best we can think of is Flexseal tape. Does anyone know in more detail what the tank is made of, and what would work best to patch it?
 

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Naildriver
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The welding kit will work pretty good. If you have larger areas that can't be tacked with the welding iron, for the same price you can buy Q-Bond. It has a liquid that you will pour in the crack and a powder that you sift over the wet part. It gets rock hard and can't be scratched with a knife once cured. You are draining the black water out first, right?? 🤮
 

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Discussion Starter · #5 ·
The welding kit will work pretty good. If you have larger areas that can't be tacked with the welding iron, for the same price you can buy Q-Bond. It has a liquid that you will pour in the crack and a powder that you sift over the wet part. It gets rock hard and can't be scratched with a knife once cured. You are draining the black water out first, right?? 🤮
That sounds great except that the crack is in the bottom of the tank and we're not able to drop it. Is the liquid thick? could it be squeezed upward into the crack and stay? (PS yes draining and cleaning the tank.)
 

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Naildriver
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So pulling the tank is out of the question. The Q-bond needs a little gravity to work properly, so upside down is doubtful.
 

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Contractor/Engineer
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The welding kit will work pretty good. If you have larger areas that can't be tacked with the welding iron, for the same price you can buy Q-Bond. It has a liquid that you will pour in the crack and a powder that you sift over the wet part. It gets rock hard and can't be scratched with a knife once cured. You are draining the black water out first, right?? 🤮
Sounds like super glue reacting with baking soda - seriously... rock hard.
 

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Naildriver
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super glue reacting with baking soda
Not sure. The powder looks similar to gun powder. When I saw it being used, the guy had a split in a tractor hydraulic line near the fitting. After sprinkling the powder on the liquid, it was a mere 3 minutes and they had to actually grind it down with a dremel so the fitting would slip over the area. Super bad stuff, IMO.
 

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How many gallons is the tank? All those acrylic adhesive tapes are pretty rugged, Zip System, Flexseal, etc. I've used them in watertesting tank setups holding back 30+ gallons and they didn't stretch at all, long way from failure. Plastic welding works well too when you get the hang of it but is slow going, even with a 250 watt iron. If using adhesive, clean the surface with alcohol and/or naptha before applying.

Also, you'll want to drill out both ends of the crack regardless of what you use to fix it, or the crack will likely continue to spread.
 
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