Thanks chris, the problem with pressure guages attached to your mains as June from gaps water explained is that they often give a higher reading and are inaccurate. A hose supply to your van will also alter this. I tried a guage on my mains tap and it read approx 70 - 80 psi, she suspects its more like 40. I have a small static system in a first floor 1 bed flat with merlin ro, horrible waste ratio and product of 37 ppm ( my supppy is 350 ppm). I'm looking at a substantial investment ( for me anyway) with buying a twin 4040 ro to install on the van as my workload has increased 3 fold since I started a couple of years ago. Its no longer viable for me to produce statically in such a confined space and neither is it to my neighbours. I have several friends and properties where with the correct quick filling equipment in place I could produce pure water on board the van as and when I need it. I asked gaps water as to the expected production and fill times and these are not set in stone ( these are not only relative to pressure and tds but also to what dissolvable solids make that total), hence June suggested this idea as to give me some realistic expectations as to how well their products or any 4040 ,for the matter, would perform ( a very honest answer I think you'll agree).
Thanks for the reply and kind offer anyhow.
Simon