I received the 90 degree sewer fitting today and it checks out OK!
The id of the tank inlet and the od of the fitting are a perfect match.
Seeing as how sh** runs downhill I thought the angle of the dangle was kinda important
Short update after two weeks in the van with a family of four:
- Don't bother with Sikaflex on the toilet. It doesn't seal. The Dow 731 (from McMaster-Carr) is working well. Lay a thick bead though.
- Smells are not too bad, especially with the Thetford Campa-Chem. Flush with the lid closed.
- It's a really tiny seat. The one at home seemed huge by comparison.
- Capacity is tight. Our family of four needed to dump every 36 hours or so (pandemic kept us out of other places.) The advantage is that during our trip there were only two obvious places to dump a black tank, while this can go almost anywhere.
There is a special pink fluid, but from what I've read it seems to create (or dislodge) black mold in the pump system. Pretty hard to find in any case.
I can report that one season with 100% RV antifreeze -- a blend of propylene glycol and ethanol -- yielded no damage. I would try to find the stuff with less alcohol if available. This makes the cassette useful year-round.