Complex sentence: In the public supply of water this is an undesirable property, in (usually older) consumers' premises plumbosolvent water can attack lead pipes and the lead in solder used to join copper and steel pipes leading to increased lead levels at the tap.
Split into simpler sentences: In the public supply of water this is an undesirable property. In (usually older) consumers' premises plumbosolvent water can attack lead pipes and the lead in solder used to join copper and steel pipes leading to increased lead levels at the tap.