A minimal amount of scale formation that looks like a fine dust is OK. Excess Scale forming on pool surfaces or equipment is an indication of too high a Saturation Index (greater than 0.5). This is caused from improper water balance.  See Problem Water Balance/Saturation Index.

TREATMENT

1.) Test water factors and balance water before it is too late.  See Problem Water Balance/Saturation Index.

2.) If all factors test Perfect, see a pool professional about Scale Inhibitors.