A "Salt Water Pool" is not a chlorine free pool.
Salt water chlorination is a process that uses dissolved salt as a store for the chlorination system. The chlorinator uses electrolysis to break down the salt (NaCl) producing hypochlorous acid (HCIO), and sodium hypochlorite (NaClO). Incorrect use of a salt water chlorination system can cause dangerously high levels of chlorine in a swimming pool.
Due to the way in which chlorine is generated in a "Salt Water Pool" there is no traditional "chlorine smell" or eye irritation (actually chloramines). Therefore a pool may have excessive chlorine levels without these indicators. These levels may dissolve threads and/or bleach swimsuits, towels and vinyl liners. These levels may also corrode stainless steel and degrade coping and decking.
Weekly testing of chlorine levels is mandatory.
Chlorine generators may constantly be adding chlorine to the swimming pool, in some cases the high chlorine level may bleach the testing agents causing false negative chemical readings.
Saltwater pools require properly "balanced" pool water. This includes stabilizer (cyanuric acid) to ensure the proper sanitizing function of the chlorine and the maintenance of correct pH (between 7.2 and 7.8 ppm)