Water is fundamental to life. Historically (link), in times of drought places that have water are scenes of intense evolutionary pressure, places that don't have it are abandoned. Without it cities have been moved or deserted, civilizations have collapsed.
Plastic
In Australia plastic tanks and plastic liners must be constructed of materials that are at least of food-grade standard (compliant with AS 2070) and if the water is to be used for human consumption the plastic material must actually comply with the requirements of potable-water standard (AS/NZS4020).
Apparently though plastic tanks make for acidic water. Acidic water reacts with copper pipes and does nasty things to you. Either flush the pipes before drinking the water or don't use plastic tanks.
Fibreglass
Fiberglass storage tanks are widely used in the chemical and food industries to store various products. For food products, the FDA (U.S. Food and Drug Administration) weighs in. Any resin used in the manufacture of food product storage needs to be FDA-approved. The ABYC mirrors this requirement in its potable water standard H-23.
Concrete
Leaches chemicals
