Can levels to high

[Aaron88]

Switch to distilled water for the test.

I will give that a try and see what happens.

This may be a stupid question but for the sake of learning, I will ask. What is the difference between distilled, R/O, and D/I water?

 

[Randy Holmes-Farley]

I will give that a try and see what happens.

This may be a stupid question but for the sake of learning, I will ask. What is the difference between distilled, R/O, and D/I water?

The Hanna checker for calcium is, IMO, a poor design that requires very low levels of calcium in the blank, otherwise the calcium levels in the tank water will read too low. Less than 1 ppm in the fresh water used, which might be present in some RO/DI water, will cause false low reading.