Water supply, sewage, plumbing and sanitation during the Middle Ages

What's the best case scenario possible for Europe in the Medieval times, when it comes to water management? Historically, European cities were ridden with many diseases. While bathouses were present in the Early Middle Ages up to the appearance of the Black Plague, it would have helped tremendously if European houses had a running water, plumbing and waste management systems.

What interests me the most, at this, are the pipes. While the Romans did use lead pipes, it isn't the healthiest material you could use. What about plastics? Would the medieval Europeans be able to develop it at all? Not to mention sewers, which would also help a lot.

So, what would be the best way to achieve at least some of these?
Many Medieval Cities had roots back to Roman construction, repair old infrastructure for the sewers and the Aqueducts to feed them, and then expand the system to new construction.

It's a tough sell.

Problem with lead pipes is overstated, that's a long term problem, when Dysentery, Typhoid fever, and Cholera are short term.

2nd point, that Roman system were continuous flow, so little time for Lead to leach into the water. The Roman love for Lead Acetate as a food sweetener was a bigger problem