Hi Pat

You say that I may want to lower SWCG from 50% I assume to extend it's life, but then I'd need to circ longer thus more power, guess it's a trade off.

Keep pH in 7.2-7.6 so don't think that's why etching.

Similar to you, pool builder added salt about 1 month after plaster & fill.

Thanks for ideas . . . cheers.