Fixing Black and Grey Water Tanks

[JustJosh]

Earlier in the spring, I actually succeeded (on the third try) fixing my black and grey water tanks which were both cracked at the top of the pipe where it meets the tank. There are a few videos on Youtube with recommendations involving a combination of fiberglass and ABS glue. This method just didn't work for me. Maybe operator error, but it would appear to work and then it just wouldn't hold, and I had to clean the area off with a multi tool and start over again. This method just didn't work for me.

 

Here is what did: heat welding. Here's the basic steps.

 

1. Figure out what kind of plastic your tanks are. My understanding is that this is usually either ABS or Polypropylene. This in of itself is a bit of a trick. See: https://engineering.stackexchange.com/questions/6682/how-to-determine-whether-plastic-is-abs-or-polypropylene

 

2. Buy a hot air gun style plastic welder. These work best because it's easiest to get the tank and the welding plastic up to a temperature where they will seal together. This one worked fine for me: https://www.ebay.com/itm/254290766066. Do not buy something that looks like this: https://www.ebay.com/itm/311585701819?hash=item488bf47fbb:g:CvoAAOSw7GhelqBr. I tried these, but they just didn't work because it's not possible to get the tank and welding plastic hot simultaneously.

 

3. Buy the appropriate plastic for the repair. In my case, it was ABS.

 

You will need a sheet of appropriate plastic. I used this: https://www.amazon.com/Pack-Plastic-Moldable-Textured-Technology/dp/B08RXJHJK7/ref=sr_1_2_sspa?dchild=1&keywords=abs+plastic+sheet&qid=1623637610&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExMFM0NFQ2SEJWRUxSJmVuY3J5cHRlZElkPUEwNzM2MjE0MkhWMVRSVTNEMFBTSiZlbmNyeXB0ZWRBZElkPUEwNzUzODYyWlFHU1hXMlU3S0lTJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

You will also need some welding rods. I used these: https://www.amazon.com/Matrisen-50PCS-Plastic-Welding-Rods/dp/B08VHLV97S/ref=sr_1_1_sspa?dchild=1&keywords=abs+welding+rods&qid=1623637644&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzNFRJVjJSTlk1V1dNJmVuY3J5cHRlZElkPUEwNjQ5NzU5T1NDR0ZQVzFKUkFDJmVuY3J5cHRlZEFkSWQ9QTAxNzA4NjkyNTBNTjlENU1JMjJQJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

4. Heat the tank area with crack. Keep the heat steady and push some of the plastic welding rods into the crack. They should melt quite easily as you push in if your heat is good. BUT, don't get it too hot or you will ruin your tank completely. Let it sit and cool. 

 

5.  Heat up the repair area again, and then weld a custom cut piece of the plastic sheet over top of the entire repair area. Let it cool. 

 

6. Melt some more plastic rods into the seam between the custom cut sheet and the tank. Let it cool completely. I mean 100% completely. Then, check your work by throwing a gallon of water in it and letting it sit. 

 

I strongly suggest goofing around with the rods and heat gun and do a few practice welds before doing it for real. Also, don't rush. Also, also, apologies for not taking pics or videos. 

 

 

 

Edited June 14, 2021 by JustJosh

[linda s]

I'm glad you found something that worked for you but I fixed my black tank with fiberglass and abs glue many years ago and it's still solid as a rock. Not a little crack either. Truck dropped firewood in the road in front of me and it took out the entire side of the tank drain tubes included. Lots of poopy in the road but I just kept driving. I covered the entire side of the tank and had to drill a new hole in the wall I made for the drain tubes. The key for this process is to make a thick slurry out of ground up abs and glue and use a very open weave fiberglass mat. Does not work on polypropylene tanks at all though and the plastic weld is the way to go. Options are always good

Linda S

[JustJosh]

My mistake with the fiberglass method was probably not getting a good enough slurry and too tight a weave on the fiberglass.