Some types of stone can suffer from weathering from the (sodium) salt water used with electrolytic chlorination, as the salt forms crystals as it dries. These crystals form inside the small ‘pores’ in the stone and erode it over time. These pools are often set up to use ‘fresh’ water and liquid chlorine instead of salt chlorination to minimise the problem. Unfortunately, so called ‘fresh water’ pools often get naturally quite salt as salt is continuously added from the mains to replace water that evaporates, leaving its salt behind. In addition, salt is added with the liquid chlorine. Eventually, even ‘fresh’ pools may erode your stone and the running cost and inconvenience of running liquid chlorine pools is substantially higher than that of salt chlorination. In fresh pools, you really need to change the water 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 and does not form crystals. You can also use salt chlorination with standard salt chlorination equipment and the water is nicer, softer and much better with hair. Magnesium baths are reputed to help tired muscles as well.
There is a small cost to change over and a slight premium per annum for magnesium compared with sodium (common) salt
Our experience is that sandstone is not appreciably affected by magnesium pools over many years, however, we cannot make any guarantees in this regard.