Well after your post I made a unit from a new drain pipe, capped the bottom after putting an 'inlet' for the water just above the base and an outlet at the top. The unit was about 3 feet in length, filled it with 5 ltrs of resin which made it about one third full and on a slow flow - and I mean slow, it produced about 300 ltrs in a 24hr turnround at 000 TDS from a tap TDS of 44. I thought it was the beas knees - until it rained! My tap TDS went up to 170 and my water up to 76 max

According to the boys who know about water that is the way it goes and why you need a RO system. Using resin only uncompressed will make the water find the shortest way out and therefore not maximise the resin. The answer is to pack it very, very tight into the container, cap it in some way, add a filter unit topper to slow the rate even more which makes the water use all the resin to permeat thro thus using all the resin to clean. I have yet to find a way of packing the stuff in tight, but I will! I possibly need a narrower or shorter tube?
I presume you are having more luck than I did

Even tho I say it myself it was a pretty impressive looking system and pre the rain was very good at producing 000 TDS water . I think the problem round here is the rain is all run-off from the agricultural hills and is full of rubbish and chemicals once into the system

JohnL