Water containing salt in concentrations of 5,500 to 6,500ppm is mildly corrosive, but as all chlorine is made from salt, conventionally chlorinated water is corrosive too. Whereas saline water has no harmful effects at all, impurities in chemical chlorine can damage pool surfaces. Most leading brands of filters and pumps are not affected by mildly saline water, and carry warranties to that effect. Modern corrosive resistant materials such as UPVC should be used in plumbing, as is now customary with any water treatment systems. Sea water has substantially higher salinity levels, and in such cases, the usual special precautions need to be taken against corrosivity.