Some types of stone can suffer from weathering from the salt water used with electrolytic chlorination, as the salt forms cystals as it dries. These pools often use ‘fresh’ water and liquid chlorine instead of salt chlorination to minimise the problem. The running cost of this is substantially higher than that of salt chlorination and far less convenient and requires water change every few years to minimise built-up salts from evaporation.

One alternative you may wish to consider is to use magnesium salt instead of common (sodium) salt.  Unlike salt, magnesium never dries out to a solid and does not form crystals.  Our experience is that sandstone is not appreciably affected by such pools, however, we cannot make any guarantees in this regard.