Ozone purification is cheap but could allow for future contamination if there is backflow or possibly a leak in the water mains. Chlorination prevents anything

Ozone purification is cheap but could allow for future contamination if there is backflow or possibly a leak in the water mains. Chlorination prevents anything from growing in the water from the filtration plant to your home. One problem that major coastal cities have is that they collect water from streams that have already been polluted and are on their way out to the ocean. The US has a lot of these cities, 40% of the population occupy the coasts which is only 10% of the country. The cities in the US that typically are regarded as having the best tap water are midwestern cities, ones that do not have a coastline and tend to get cleaner water from natural sources. Switzerland, Austria, and Germany are exactly the same. They are very central countries with nearby access to Alpine runoff water, the water they get is pretty unmolested when compared to what the Potomac River supplies to Washington DC.