I just refilled my tub and I used softened water this time because I wanted to try having some salt in my water and I figured that was the easiest way. I guess I could have crushed up softener salt and added that to the spa instead.
The softener removes most of the calcium from the water.
I understand that some pools need calcium in the water to prevent it from taking it from the pool shell.
Do I need calcium in my spa water even though the spa has a plastic shell?