Welcome to our forum.
We filled our new tub Sunday, just to get in it (no chemicals), and noticed the same ring as you describe. It came off easily with a sponge.Monday morning I drained the tub and got all the needed chemicals from my dealer. When I refilled the second time, the ring immediately reappeared. I added stain and scale control and calcium hardness to the tub, along with the alkalinity increaser and bromine.This morning, no rings
....The manual states that low Calcium Hardness can cause staining. So has anybody else dealt with this staining/discoloration? How should I remove it?
The best cleaner I've found for cleaning the waterline is found by scrolling down here: Tub Rub. Works like a charm and easy too.
Be careful what you use, and check with the spa manufacturer as this may also void your warranty.