Finally got my IBC set up in the garage and swapped all the filters etc from van.
600 litres used to take 10 hours to make so 1000 litres going to take nearly a day 
. ... as well as using resin faster due to 4040 not operating at max capacity
Tap pressure now measured at 42psi so now need booster pump.
Can anyone suggest a good booster pump ?
Ian this is the one i have........
put the following into ebay search box.........#180587954359
Mine came with a pressure tank and adjuster, i'd have a word with them see if they can still get them. My gauges show 80PSI across both pre filters and i produce water at about 4/5ppm. I aint getting anymore DI resin wwhen my bag runs out !!!! And its fills quick !!!!
That pump may well work just as well without a pressure tank as i believe the tank is just to keep the pressure constant. But i think the RO membranes pretty much do that anyway as there is only so much you can shove through them and most if not all 4040 RO's are capable of what that pump pushes. As far as i know you do need a good water flow as that pump will consume (forget what it says it can pump) about 6 litres a minute when pushed at pressure through an RO so your supply will need to be able to keep up. If not you'll need a header tank.