I changed the water in my spa about six weeks ago and have been having trouble getting the PH in range. Last weekend I used the spa and the surface feels like sandpaper. The rough surface can rub off but I don't know what has caused this reaction. Any ideas?
Butch

Using calcium hypochorite(pool chlorine) can do it. Also, high ph produces a scaling effect.

How do you get rid of it. I have the same problem.

lower the ph of the water for several days. Don't go too long with acidic water, can affect equipment.

In a perfect world, you'd plug off all jet and suction openings and lower the ph and install a submersible pump. Run the pump for a few days, moving the water until the scale is in solution, then dump the water and refill.