Was expecting the ro to get down to about 12, and it seemed to settle around there, then it got to 10 and that pleased me no end, about a day later it was down to 8, a day or 2 later imagine my joy when it hit 5, later still it was 4 and has been for about a fortnight, and just looked tonight and lo and behold its on 3!!! Wow! I don't know if any of it's to do with fluctuations in the tap water time will tell, in any case I've not changed resin since I put them in, been on 1 for weeks, would be 0 but obviously it had a bit more hammer at the start. I tell you, I would die for these membranes!