So far i have spent £225.00 on resin. They are TDS Colour change filters( That's my only gripe) that is from June last year. No part's have broken or have had to be replaced. Per fill 650lts it's around £1.25, but that's per 1000lts. The rejection rate on the pro 6 is a lot lower than say a pro 5. So roughly £300 a year on water £225.00 on Resin filters. I haven't had the water rebate yet as I'm still talking to the water board. Water is calculated that 98% goes down the drain the rest is for drinking and cooking so a rebate is due. Don't take to closer look at my water figures as im still not to sure myself yet. Hope that helps.