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I used softened water in mine to fill as it's easy to get hardness in, but impossible to get it out once it's in the tub. You can add the calcium hardness 3-4 ounces a pop until it's where you want it. Not adding it can cause the water to try to leech it out of other things like metal parts. Mine came up after 2-3 times adding CH. It won't change much after you get it there.Like others said...nothing to panic over. You can't really mess it up and if you do...just drain and refill!