Out of interest how long has your Race Glaze Filter gone on the original filter granules? Due to the cement dust issue (now sorted) , I must have washed it and the wifes say 40 times. It still seems to prevent the limescale look. But as I always blow dry her immediately afterwards its difficult to tell if its still 0 PPM If memory serves me well I think they said I should get 36 washes ( well rinse-downs) out of a filter. As its been clayed, da polished and followed by 4 coats of Collinite 476S for the winter, I dont fancy doing the acid test of washing, then filter rinsing and then watching to see how it dries! I guess as I can not see any limescale whiteout, its doing its job. I lost the instuction on how to change the granules. I guess its pour out the old ones and flush them out and then replace. . At £40 its a shame its not just a cartridge swap out.