Here in Higuey most water is delivered by water trucks that fill cisterns, as there are virtually no public aquaducts here. There are tens of water companies. They usually pull the water out of the rivers. Most of the water is not potable, but it is OK for washing, bathroom, etc. We buy potable water in 5 gallon plastic bottles.
Be careful if the water company says the water is potable. Most likely you can get ahold of companies that do osmosis cleaning, and they can deliver by truck. But it will be more expensive than a regular water truck.