New TDS Meter - reading of 21 from Calgary Water?

[wayner]

Just got a TDS meter from jayson (Milwaukee Brand) calibrated at factory, I tested last night, I have a Kent RO/Di unit, cartridges haven't been changed in 8 months, all of them, I placed the meter in my holding container and got a reading of 1, then i placed the meter in a glass of Tap Water and got a reading of 21, Is this possible?, City of Calgary water at 21?,

The other thing I don't understand is that I haven't changed the sediment filter which you think would be Brown by now, it's still pretty white, does Calgary have that good water?