Scale 

PROBLEM: Rough, sandpaper-like deposits on the pool’s surfaces.  Scale may also build up inside the circulatory plumbing, especially the heater.  This condition leads to reduced circulation, loss of heater efficiency, impaired equipment operation and clogging.
SOLUTION: Adjust and maintain pH to the acceptable range of 7.2 to 7.6 (Ideal range is 7.4 to 7.6).  Take water sample to A.C. Swimming Pools for possible adjustment of total alkalinity and calcium hardness.