The pressure tests and claims made on these check-valves is based solely on my personal experiences with the ones demonstrated in the video. Individual results may vary, and caution and care should be taken when loading the valves with high pressure. The risk of higher pressures is that the balls may be forced from the adaptor, shooting out like projectiles. High pressures may also cause the ball to lock up, preventing normal operation of the valve, or possibly even structural failure of the valve altogether. These valves are not made, or claimed, to be used in any heavy duty operations. Use of this content is at your own risk.
I wanted to build a PVC water pump, but the check valves were around $10.00 each. That seemed a little steep for a PVC build, so while looking for alternative options, I settled on this design, which is about the cheapest, while still being practical and useful, that I could imagine.
In my testing, the valves work great with air and water. Air pressures up to 60PSI seemed to be fine for normal operation, while pressures above 60PSI occasionally caused the ball to lock into the O-Ring, and required substantial "back-pressure" to unlock it.
If you try using rubber bouncy balls as the valve mechanism, only use them in very low pressure applications like blowing up balloons, and possibly for improvised water guns. Relatively high pressures used with these balls seems to eventually force them out of the adaptor, and can shoot them out at surprising velocities.
Overall, I'm really happy with the valves because they can be fit into any part of a PVC system, and can be duplicated quickly, easily, and for very very low cost.