Build up on tile


May 29, 2020
I recently added some calcium chloride to the pool as my level was 225 which had dropped from 300 from last summer. Then I noticed the following day after addition that my pool has this scale right at the water line. I tested the water today:

pH 7.5
FC 7
CH 250
TA 100
CYA 30
CSI -0.29 (pool math calculated)

I added muriatic acid today to drive pH down to 7.3. I use liquid chlorine typically but for the past 3 weeks have been using 73% calcium hypochlorite for slam to try to drive the calcium hardness up.

we had the tile bead blasted last summer and had been maintaining without any scaling issues afterwards.

Tried to use muriatic acid 1:3 first with some improvement but then once it dries or water contacts it again it scales. splashed a little muriatic acid directly on the scale and also no change.

Any thoughts for cleaning it up or will the chemistry just dissolve it again with frequent brushing and tight pH control and going back to using liquid chlorine.
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