Worst Case Scenario - Black Water Tank Leaking

An old repair on mine had failed (it was repaired long before I bought it). The back corner of the tank was basically glued back on with epoxy. I suspect a tire blowout. When it started leaking I scraped off the old repair and used this stuff:

Plasti-Mend

It doesn't just stick to the outside of the plastic. It melts into it. It's crazy - and it's effective and permanent.

+1 for plastimend. I have used it and Plastimend really works. Permanent fix for black ABS tank.

Moved to Tech Issues forum from DIY.

+2 for Plastimend also. This stuff is great. I fixed a crack in the black tank at the outlet pipe. It's better now then when it was new.

First step FIND THE LEAK is it a split seam. a puncture. a leaking seal on a valve What. True story follows (short).

Then depending on the nature of the leak the fix may be as simple as draining the tank drying the area (Hair dryer works after a alcohol swab down) and GOOP an adheasive sealant that really works.. Or Eternabond.

The story
Bad smell in RV after black tank used first time
Upon investigation when they built it they put the tank in Then the floor Then the walls. the walls were screwed to the floor with VERY LONG screws (the carpenter was too busy to go back for the proper length) and ... Screwed right into the black tank.. NOT GOOD. had to tear down and rebuild with new tank new floor and shorter screws. UNDER WARRANTY too.

I had both my grey and black tank crack a few years back (not at the same time) Black tanks are usually made of ABS. A little Google and I discovered and very successfully did a PERMANENT (so far 5 years) solution.
1-Get a small chunk of ABS pipe and chop it into small flakes. The first time I did this I just used tin snips. The second fix I used a step drill and drilled many holes in an elbow that generated a big pile of stringy little spiral flakes (This worked best!!)
2-Put the flakes into a small GLASS jar with a lid and add a bit of ACETONE
3-Over about 5-10 minutes the flakes will turn to paste (just add more flakes or acetone to get a smooth, thick syrup)
4-Clean your crack ;). Maybe even drill a small hole at the end of it to provide a radius end, even open it up so it is a small V.
5-Schmear the syrup in. As the acetone hits the tank it will eat into it and then as it evaporates it actually welds the tank. You can build up several layers if you need.

This works well and is cheap!

TURNKEY wrote:
I had both my grey and black tank crack a few years back (not at the same time) Black tanks are usually made of ABS. A little Google and I discovered and very successfully did a PERMANENT (so far 5 years) solution.
1-Get a small chunk of ABS pipe and chop it into small flakes. The first time I did this I just used tin snips. The second fix I used a step drill and drilled many holes in an elbow that generated a big pile of stringy little spiral flakes (This worked best!!)
2-Put the flakes into a small GLASS jar with a lid and add a bit of ACETONE
3-Over about 5-10 minutes the flakes will turn to paste (just add more flakes or acetone to get a smooth, thick syrup)
4-Clean your crack ;). Maybe even drill a small hole at the end of it to provide a radius end, even open it up so it is a small V.
5-Schmear the syrup in. As the acetone hits the tank it will eat into it and then as it evaporates it actually welds the tank. You can build up several layers if you need.

This works well and is cheap!

Wow!!! This sounds great! I noticed the product suggested by everyone here is acetone and MEK p. So... Similar idea. I'd like to try this just to see it work.

Opening up the bottom of the TC tomorrow. Got delayed by the holidays.

Looking forward to handling the standard fiberglass insulation down there that's so soaked with sewage it was dripping out of the seams ok for the RV with every flush.

I'll stick with the tread title. Worst case scenario. Ha ha ha

Well, I opened up the bottom.

I filled up the tank all the way to the bowl of the toilet and NO LEAK!

Unreal. Sewage was dripping out of the bottom of the TC last time my girlfriend flushed.

We stopped using the tank for about a week, keeping it empty. I rapidly poured a full tank of fresh water into it through the toilet. 6 gallons at a time.

Now no drips.

I'm lost.