hi guys i bought a 200gpd ro unit from pure freedom on ebay and got it for a good price also bought a di vessel but i have hardly used it in fact it has only been working for the last month and i dont mean like a work horse either 4 days a week max to get me the required amount of water. and at first it read 0 reading and just today horified to see it read 9 tds and that was straight out of the pipe into a glass, so i did it again with the same reading so i was wondering would i need to keep changing the resin every month is this rgiht. please give good advice, also is this ro machine any good. cheers mike