Hi everyone, just a quick question is anyone using a GAC Pre-Filter on there systems? Only i have never used one on mine, i noticed gardiner do a 20" version which would be what i need, now what benifit does this serve and would it be worth my while getting one? Does it help reduce PPM before the RO that much? Also at what stage of filtering are you placing this GAC filter? Before sediment and carbon filter or after?