The purpose of having a water tank in the house is to provide a necessary component of a well or pump water system. The water tank contains water drawn from the well and distributes it throughout the home plumbing system.
A water pressure tank helps to distribute water throughout the home. Water pressure tanks use air pressure to force the water out of the tank and through the pipes. Water storage tanks serve only as a place to store large quantities of well or rain water for future use.
Water tanks often use a pump to aid in distributing the water and to create air pressure in the tank. You can monitor air and water pressure with a pressure control switch.