"will probably get a water
specialist to give me their thoughts as I know some of the worlds best" Me too. Look into Spectras 150 Ocean rowing unit. It's about the only thing that makes sense. Making your own, seen it done a few times did it myself many times. I promise you, the time spent getting a DIY
one to work
, especially under your parameters, is better spent working at McDonalds at far less hours earning enough money
to just buy a new and proven system.