Corrections must be made to derate all PVC and CPVC pipe, valves and fittings when operating temperatures are expected to exceed 73 degrees Fahrenheit.
The working pressure is directly affected by temperature changes. The drop in pressure capacity can be calculated using table 3. Multiply the maximum working pressure by the temperature correction factor for a known temperature.
Example: For 2″ Schedule 80 PVC fitting, the maximum working pressure is 243 psi. If the operating temperature is known to be 110 degrees Fahrenheit, the correction factor can be found on the chart to be 0.50. The adjusted working pressure would then be 243 x 0.50 = 121 psi.
The chart below is to be used to determine recommended pressures. If you have any questions regarding your system, contact your architect or designer for proper system operations.