Question

why are lead pipes not used for domestic water supply

Answer 1

Lead pipes once were common in household plumbing and municipal water service lines, but concerns about lead poisoning from drinking lead-contaminated water led Congress in 1986 to pass the Safe Drinking Water Act that banned use of pipes, fittings or solder containing lead in new plumbing installations providing drinking water. But if your home was built before 1986 or is served by a public water service connection installed before 1986, you could be dealing with plumbing containing lead