ASTM D1785

Covers — rigid PVC plastic pipe in Schedules 40, 80, and 120 (IPS dimensions) for the distribution of pressurized liquids at temperatures up to ~140 °F, defining material cell class, dimensions, and pressure ratings.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Higher-temperature CPVC pipe → ASTM F441.
• PVC fittings → ASTM D2466 (Sch 40) / D2467 (Sch 80).
• Compressed air/gas service → not permitted for PVC (safety).
• Buried water-main PVC (DR/PR, gasketed) → AWWA C900.

PVC pressure pipe is for liquids only, never compressed gas, and derates strongly with temperature.

D1785 sets minimum requirements for PVC pressure pipe:

• Material — PVC cell classification (e.g., 12454) governing strength and chemistry.
• Dimensions — IPS OD with Schedule 40/80/120 wall thicknesses.
• Pressure Rating — by size and schedule at 73 °F, with a temperature-derating multiplier.
• Testing & Marking — burst/sustained pressure, flattening, and product marking (including "not for gas").

ASTM D1785 is the schedule-based standard for rigid PVC pressure pipe (Schedules 40, 80, 120). Dimensioned to iron-pipe-size, it shares outside diameters with steel pipe of the same nominal size, and its pressure rating falls as size increases at a given schedule and derates sharply with temperature (PVC tops out around 140 °F).

Joints are made with solvent cement (fittings D2466 for Sch 40, D2467 for Sch 80) or, for Schedule 80 only, threading. A critical safety rule: PVC pressure pipe is for liquids and must never be used for compressed air or gas.

Engineering Note: Never use PVC for compressed air/gas, and apply the temperature-derating factor to the rating — a Schedule 80 pipe rated at 73 °F loses much of its pressure capacity by 120–140 °F.