Section P2603 of the IRC Part P (Plumbing) establishes requirements for water supply system design. Water supply is provided to the building from either municipal water mains or private wells. The water service pipe entering the building must be sized to deliver adequate water pressure and quantity to all fixtures. Minimum water pressure at point of use is typically 20 pounds per square inch, with maximum static pressure of 80 pounds per square inch (requiring pressure reduction devices above that level). Water meter installation is required where municipal water is supplied, and the meter location must permit easy access for reading and servicing. Branch lines are sized based on the number and type of fixtures they serve, using fixture unit calculations. One fixture unit represents the water supply demand of a single water closet (toilet). Lavatories and sinks are typically 0.5-1 fixture unit. Showers are 1 fixture unit. Hot water heaters are sized based on the quantity and type of hot water fixtures, with typical sizing of 40-50 gallons for single-family homes with moderate hot water usage. Hot water pipes must be insulated to reduce energy loss and improve efficiency. Cold water pipes may need insulation in certain climates to prevent freezing. Water distribution piping is typically copper, PVC, PEX, or other approved materials. Piping must be supported with clamps or hangers spaced no more than 32 inches apart for copper or plastic supply lines.