It was the supply switch in combination with the state of the pipes. I believe the switch of the supply caused a layer of calcium coating the inside of the lead

It was the supply switch in combination with the state of the pipes. I believe the switch of the supply caused a layer of calcium coating the inside of the lead pipes to dissolve due to a different chemical makeup, leading to water then being exposed to lead. Had they not switched on the first place, they would have been ‘ok’. Not great for sure but they would have had time to deal with it. Which they probably wouldn’t have had money to..