The air regulator needs to be at 140psi so that we are below the maximum of the blue hose (MAWP stated below). All other items are rated higher than the maximum pressure of our standard air compressor can produce. The diaphragm gauges in the water system lines only see a maximum pressure 80-90 psi and 60-70 psi. If someone were to deadhead the system and left the air on only then these gauges and rotameter could see a higher pressure of 140psi. Also, someone would have to set the air regulator higher than allowable.
Blue hose = MAWP 150psi
Legris fittings = MAWP 290psi
Cash valve = MAWP 250psi
Air gauge = 0-300psi
Diaphragm pressure gauges = 0-160psi