Went to fill up my small 5lt air tight container with some resin from my container i store my resin in and cant believe how well the resin has lasted this year. i brought a 25lt bag in january and about 10 months on i still have over half left in the bag! so my costs for my RO has only been £45 for 10- months, thats only coz i had to change the pre filters a few months ago. all this with water at 450ppm to start with!!!