Right, my ro gets tds to 1, resin obviously lasts a while at that, and 1 is fine to clean with, ok. I've about 8 litres of resin, but only a 0.75 holder, which I'm not altering. Problem is i expect in the next 6 months the ro wont be as effective but I've heard resin goes off after a while, so do I keep changing as soon it hits 1 or just hope the resin holds its own? Oh, RC, I know you have a panic attack at 1, so know your answer /emoticons/smile.png