There has been a lot of posts on building a holding tank. Large sections devoted on some of the sites.
Well from all that this is what I came up with.
Thanks to all have gone before me and showed there work.
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That's almost exactly the way I did mine, except I used a metal tank. I also used black polyurethane sealant under the flange to help stop any leakage.
For the flex between the toilet and the tank I used a flange on the toilet that had 2 rubber seals on the outside of a 3" tube. Those slipped into 4" flange on the tank and seal very nicely. Now when the bus flexes going down the road or the floor under the toilet flexes with my fat arse adding weight there, the connection flexes back and forth and keeps the rest of the system from moving.
Looks good! keep up the great work!
Dallas