Quote Originally Posted by jstonemo
It is vinyl. I didn't test for hardness because it is a vinyl pool. I will do it if someone here thinks it would be important to know the numbers.
Nope, it's not important. So long as the water isn't touching any plaster or grout, you not only don't need calcium, but you can stay with the alkalinity and pH that you are at now. If you find that your pH swings more than you want from the addition of chlorine, you can always bump up your TA a little (perhaps to 80). If you wanted to go higher than that in TA, you may need to set your pH target higher as well. As it is for now, if you're happy and the pool's happy, enjoy!

Just be sure to keep your chlorine at the minimum levels recommended by Ben's Best Guess CYA chart which it looks like you are doing.

Richard