Section P2801 of the IRC Part P (Plumbing) provides general requirements for water supply and sanitary drainage. All plumbing fixtures must be water-efficient, meeting EPA WaterSense or similar standards where required. Water supply piping must be protected from freezing, particularly in cold climates. Backflow prevention is required where non-potable water might contaminate the drinking water supply. Vacuum breakers prevent siphoning of water from fixtures into the supply. Cleanouts in drainage systems must be accessible for clearing blockages. Pitch of drainage piping is critical, with 1/4 inch per foot minimum slope ensuring gravity drainage.