Sandpaper at the highest grit in the lining of hot tub !

[Cinders]

Hot tub has white sand granules in the bottom of it & not flakes! I had drained hot tub as I had done before, then with a clean microfiber cloth I will wipe it all down. Well this time as I was draining the hot tub and as I mentioned earlier about the sand granules that was on the bottom of it, I rubbed my hand along the inside of tub and lining of hot tub fills like the roughest sandpaper they make, even all the jet spouts/covers feel like sandpaper. When I got into hot tub with the microfiber cloth to remove as much of the white sandy granules from the bottom, it was so rough that while wiping it took layers of skin off my finger tips & caused a couple to bleed ! What could cause this? I know it is not the calcium flakes that you speak of and is there anything I can put on it to bring it back to that shiny smoothness it has above the water line? What to do & or use on lining of hot tub & what causes this ? What chemicals should I use so this doesn't happen again? Thank you ☺️

 

[RDspaguy]

It's calcium coming out of solution due to high ph/alk. Clean with acid, such as vinegar or diluted muriatic acid (beware the fumes!). If you still have water in the tub drop the ph to 6.8 and wait a few days. The flakes will come later.

@waterbear, any advice?

[Cinders]

The hot tub is empty and after a bit of research I found that a solution of vinegar and water 50/50 as you recommended and a nylon brush will work. Thank you! I'm keeping my fingers crossed, oh yeah also 2oz of defender by Leisure Time once a week , to protect it from happening again. Thanks again much appreciated! 🤞🙂