What is the Pressure Number (PN) of Shedule 40 and Schedule 80 PVC Pipe?
Schedule 40 PVC has a pressure rating of 120 psi to 810 psi, depending on pipe size, and temperature.

At 73°F the pressures are as follows:


2" = 280 psi
3" = 260 psi
4" = 220 psi
6" = 180 psi


Then as the temperature increases, you'll derate the values as such:


80°F - 88%
90°F - 75%
100°F - 62%
110°F - 51%
120°F - 40%
130°F - 31%
140°F - 22%


-Source

Schedule 80 PVC has a pressure rating of 210 psi to 1230 psi, depending on pipe size, and temperature.

At 73°F the pressures are as follows:


2" = 400 psi
3" = 370 psi
4" = 320 psi
6" = 280 psi


Then as the temperature increases, you'll derate the values as listed above.

-Source

Pressure depends on temperature, size, and schedule.