My kidney transplant recipient spouse and I have used “purified” water for over 8 years because that was safest for both of us. Bought a Zero (the best!) over a year ago and used the included tester to test the store refills and our tap water. Tap water reading was over 100 and the store “osmosis” water reading was 64. A second store’s water read 52. We love the zero and it is much more economical than buying 5 gallon store dispenser water refills! Thank goodness this product is available especially for transplant recipients! 
We use zero water in our coffee maker all the time - never have to de-scale it.  Highly recommend this product