A water heater is required for supplying potable water for showers, kitchens, bathrooms, washing machines, dishwashers and other purposes in a home or commercial building.
A water heater is defined as a closed vessel used to supply potable water, which is heated by combustion of fuels, electricity or any other source and withdrawn for use externally to the system at pressures not exceeding 160 psig, and shall include all controls and devices necessary to prevent water temperatures from exceeding 210°F. The water heater is intended to supply potable water with 100% make-up from a potable water supply system like city water.