UPDATE: 10/10/16
Just finished about 4000 miles on the road. Absolutely dry!
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I started leaking water out of the coach belly some time ago. I hoped that it would go away but apparently I am out of the Hope stuff.
In the Spring while in Las Vegas area I had a mobile tech work on the problem. He dropped the belly and found a crack in the grey tank where the tank is shaped to the valve connection. He applied a ABS repair patch type kit (adhesive and mat material) and said he hoped the repair worked. Apparently he is also out of the Hope stuff.
I finally decided that I could not do any worse. I think that I have actually done quite a bit better.
Refer to these photos.
http://s1253.photobucket.com/user/Th...?sort=3&page=1
After removing the original patch I used 80 grit sand paper on the entire area to the sides and under the valve and then cleaned the area with lacquer thinner. At this time I found a second, much bigger crack. I drilled the ends of this second crack so it would not run further.
I used pieces of sticky back sheet rock mesh tape and completely covered the area to be worked. It sticks quite well to the ABS. I then coated the tape and tank with the black ABS glue you get at any plumbing store. Just a light coat. Work the glue into the mesh tape making sure that all air pockets are worked out and make sure that the coated tape conforms to the shape of and is tight to the tank. Make sure that all edges are covered and stuck down.
After letting this coat dry I put a second layer of tape in place and again coated it with the ABS glue.
After letting the whole mess cured for a day I applied a heavy top coat making sure that all edges were well covered.
All I can swear to is that so far my work is holding.