Watching where locals get their water tells you everything about a country's water situation. In places with high-quality municipal supply, the answer is simply the tap, sometimes through a basic filter jug for taste. In many other countries, homes have multi-stage filter or purifier units installed in the kitchen, exactly like the RO systems most Indian households know, and that familiarity actually helps NRIs adjust either direction.
Water delivery is the third big model: large refillable jugs delivered to the door on a schedule, common across many countries and very economical for families. Offices in such places almost always run on dispenser jugs too. Bottled water as the primary daily source is generally the most expensive option and tends to be a traveler habit rather than a resident one.
Some regions also have public drinking fountains and refill stations, which are perfectly safe where the municipal supply is good.