Final answer:
Private water supply systems store water in pressure tanks or cisterns, which are suited to handle the volume and pressure needed for water distribution.
Step-by-step explanation:
Private water supply systems often store water in pressure tanks or cisterns. These containers are designed to hold large volumes of water and can manage the pressure necessary to distribute the water through a plumbing system. Options like plastic bags, metal drums, or glass containers are less common and not typically designed for this purpose. Pressure tanks are also used in municipal water supplies, for example, water tower tanks in cities help maintain pressure and store energy for water distribution. The design of these tanks allows gravity to assist in pressurizing the water system, requiring less energy from water pumps to move the water.