Some arguements have been made that the pressure rating on pvc is in reference to water pressure, and that it will hold far less air pressure.
I want to make the point that this is NOT true. PSI means pounds per square inch. If your PVC is rated for 280 PSI that means that the pipe can withstand an internal exterted pressure of 280 pounds per square inch, whether this pressure is exerted by water, or air, it is still 280PSI.
Now I will say it takes much less water to exert the pressure due to its density compared to air. But the rating is accross the board.
Think about this. What weighs more, a pound of feathers or a pound of bricks?
If you have a table that can hold a ton of bricks, could it hold a ton of feathers?
a ton is a ton
Just to add, because the pipe is 280 psi doesnt mean every other component you have used can safely operate at that pressure. Check your valve ratings and fittings. There are more peices than just pipe on the cannon. But as far as a rating on pipe is concerned its true to its print.
Thanks all, just my 2 cents

- Boz