"Calcium Hardness............never, my pool is vinyl"

Just because you have a vinyl pool does not mean you should never test for calcium hardness, you still need to know if it is high because it could lead to cloudiness or scaling under certain conditions. You just don't need to add more calcium if it is low.

Also realize that calcium will concentrate in the water from evaporation and, depending on the calcium content of your fill water, might not be diluted enough on water replacement which leads to an overall rise in CH. Anyone with a pool in a very hard water area like parts of Arizona or Florida know what I am talking about.