Heavy rains and warm weather have melted snowy peaks in the Andes mountains, causing landslides and nearby rivers to flood.
Chilean water utility company Aguas Andinas says the mud, rocks and trees on Sunday forced temporary closure of three purification plants.
He says about half the neighborhoods in Chile's capital of Santiago are suffering water shortages on Tuesday.
The shortage comes just days ahead of a European Union-Latin America-Caribean summit in Santiago that will bring together 60 governments.
Water utility officials say workers are cleaning the plants, water trucks are aiding several communities and the service is expected to be restored early Wednesday.