I bought this a few months ago and I can't believe the water quality is still perfect and amazing and the filter doesn't need changing, yet! I went out and bought filters and I tested the water from the pitcher and I was still getting a reading of zero! 
I am on well water and it must be an old system because there is sometimes a sulfur smell from the pipes and the readings I was getting were very high. I'm am SO SO SO glad I chose this zero water pitcher for myself.