Join Date: Sep 2013
Location: South Devon
My Motorhome: Bessacarr E725
Thanked 159 Times in 138 Posts
It sounds like bad design that some part that could fail requires the whole unit to be dismantled.
I've never liked the idea of flush water coming from the main tank.
Mine has it's own tank filled from outside. In extremis, one could fill it from a stream. With a decent solar set-up, fresh water and gas are the things that need careful management if you want to wildcamp as I do.
Regarding your problem, a vacuum breaker by design needs to be at the top of a loop of pipe. If you removed it and put a non-return valve elsewhere, what if that failed? You could have a backflow.
I think if I was in your situation, I might be looking for a way to make an access panel in the bulkhead above the loo and relocate the vacuum breaker there.
I'm daft and proud of it.