Hot Tub Gritty and feels like Sandpaper - Cause and Fix

My hot tub had a very gritty / sandpaper feeling on all of the seats. The reason for the grit was the hardness of the water (calcium) had been falling out of solution allowing it to build up in the hot tub and on the acrylic seats. The way to dissolve the calcium is to make the water more acidic (reduce the pH). My tub is approx 1100L and I put 9 gallons of regular white vinegar and approx 150g of the pH reducer in to the water and ran the jets when I could. I started Friday night and by Monday night the hot tub surface was no longer gritty and was now smooth. While I was draining the pool, I scrubbed it just to be sure I didn’t miss any undiscovered calcium and rinsed the whole tub with fresh water. I hope this helps someone!