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Water Supply and Distribution Both Codes Agree On — Cross-Connection Control and Backflow Devices, Air Gaps, Materials and Joints, Valves, Pressure, Testing and Disinfection (UPC ch. 6 / IPC ch. 6)
Chapter 6 is the heart of the journeyman and master exams: cross-connection control and the backflow devices, the air-gap table, lead limits, pipe materials and how they are joined, where the valves go, the 80-psi pressure rule, thermal expansion, testing and disinfection. The 2018 UPC and 2018 IPC were written from the same industry standards (ASSE, ASME, AWWA, NSF), so most of this chapter is shared. The differences are collected in §10 and never tested.
2018 UPC and 2018 IPC · Reviewed 2026-09-20
1. Potable water, hot water, and telling the two systems apart
- Every fixture that provides water for drinking, bathing or culinary purposes gets potable water; potable water goes to all fixtures unless the code says otherwise (UPC 601.2; IPC 602.2).
- Hot water is required in dwellings (private-use occupancies) for bathing, washing, laundry, cooking/culinary, dishwashing/cleansing and maintenance; in public (nonresidential) occupancies for bathing and washing (IPC: hot or tempered), culinary, cleansing, laundry and maintenance (UPC 601.2; IPC 607.1).
- Nonpotable outlets are posted "CAUTION: NONPOTABLE WATER – DO NOT DRINK" (UPC 601.3.2, 601.3.5; IPC 608.9.1). Purple identifies reclaimed, rain and gray-water (alternate-source) piping in both codes (UPC 601.3.3; IPC 608.9.2.1). Both use the same letter-size table: pipe through 1-1/4 in → 8-in color field, 1/2-in letters; 1-1/2–2 in → 8 in / 3/4 in; 2-1/2–6 in → 12 in / 1-1/4 in; 8–10 in → 24 in / 2-1/2 in; over 10 in → 32 in / 3-1/2 in (UPC Table 601.3.2; IPC Table 608.9.2.2). Differences: the UPC colors ordinary nonpotable piping yellow (the IPC purple) and repeats marks every 20 ft (IPC 25 ft).
- Piping that has carried anything other than potable water is never reused for potable water (UPC 604.8; IPC 608.11). Existing metallic water service used for electrical grounding is not replaced with plastic until another approved grounding means is provided (UPC 604.10; IPC 601.3).
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