if your tap water isa over 150 ppms, you need a filter. My water KILLS cannabis. Took me 6 months of shit grows to figure it out. On hot weeks, i make 60 to 70 gallons of RO water. Indoor i use about 15-20 of those gallons. Only time I have a ph issue is if I screw up mixing my water. I add 90-120ppm cal/mag and ph to 6.8. Never have a cal mag problem. Never