A. Selection Of Materials

The maximum operating pressures listed on the right are based on the hydrostatic design of the product using water as a test medium at 73°F (23°C). The maximum operating pressure can be calculated from the following equations;
P = 20t/D-t
where;
P: Pressure
D: Average outside diameter
t: Minimum wall thickness
σ: Hydrostatic design stress (HDS)
2,000 psi (13.79 MPa) for PVC Type I, Grade 1
2,000 psi (13.79 MPa) for CPVC

The following temperature corrections must be used to de-rate all PVC and CPVC pipe, valves and fittings when operating temperatures are expected to exceed 73°F (23°C). The working pressure of PVC and CPVC pipe is directly affected by temperature changes. When the operating temperature of the pipe increases, the pipe loses its stiffness and tensile strength decreases. As a result, the maximum operating pressure drop. The drop can be calculated using the chart shown on the next page. Multiply the maximum working pressure by the temperature de-rating factor for the applied temperature on site. For example, for 2″ Schedule 80 PVC pipe, the maximum working pressure is 400 psi (2.76 MPa). If the operating temperature is known to be 110°F (43° C), the temperature de-rating factor can be found on the chart to be 0.63. The maximum working pressure would be 400 x 0.63 252 psi (1.74MPa).