I need to carry much more water, but can't at the moment. Stuck with the van I have for a while (doblo).
So I'm limited to my 400 litre tank. But I need more to do ups and downs with two people. (currently ups only).
Is there an RO I can stick in the van which will produce water fast enough to plug it into a customers tap (one who isn't in

) and top up. So a couple of half hour jobs would give me a tankfull? Or would a DI fire extiguisher thing do the job? Bearing in mind the water is just about the hardest in the uk 480ppm.
I know the IPC eagle from the wc warehouse will do it but I'm not sure I want to spend 4k on a filter.
Or what about these ionics things with the filter on the tank - are they quick enough. If I got a whole new system it would be worth it.....
Ideas?