Hi Jerome;

To answer your question, just a bit pointedly: "Yes", and "In the correct order, which depends on other things". And, to answer the questions you didn't ask, "Is a hardness level of 30 ppm a problem?", AND, "Is testing by pool stores, or by test strips reliable?", to which the answers are "Yes, or no, or maybe -- again depending on your situation" AND "No, they are not reliable".

Do you have a pool you're trying to care for, or are these just general purpose questions?

If you have a pool, then hardness is not where you begin. More importantly, it makes no sense to talk about hardness out of context. So, if you've got a pool, tell us about the pool, and why you're concerned.

On the other hand, if you are just asking general purpose questions, this is not the time of year for us to be doing that. We're pretty much buried, trying to help people get pools going. I would suggest you check out "water hardness" on Wikipedia, and look through some of the pages on PoolSolutions (linked in my signature).

Best wishes,