Originally Posted by c_witch
...I have also been inclined to have on board the water purifiers that one uses for backpacking in the wilds.
Those are for removing bacteria from otherwise drinkable water. Rainwater should be okay unless your collectors are dirty. Desalination is something very different. And as stated before, hand operated desalinators are available.
(That said, we have a pur filter on our galley faucet.)