I am posting this on behalf of a friend who just purchased a house down the road which came with a pool. I have tested the water several times, and everything appears to be close, except for the calcium (CH=700). Using Poolmath, he will have to replace 2/3 of his pool water with municipal water to get it to 350. Here's my question: what are the various sources of CH? I only know of two sources: fill water (150 in my area) & PS Pool shock. We have the same water source, and I tested both his pool and tap water.
I have told him that a partial drain/fill is needed, but I'd like to isolate the source so he's not doing it more than once.
Here's the specs on the pool/tests. Please ignore the information in my sig.