Think NASA
FWIW
Spare patrs inventory is crucial to your carwash success. I learned this the loooong hard way.
Yes, I keep a spare valve for the IBA feed tank. Yes I also keep a spare rebuild kit too, just in case.
In a pinch, I would go to my local plumbing supply and ask them for a solution. They have haelped me in the past with check valves etc. The parts I got were not rated high enough psi, but they worked till I got the proper ones mail order.
I also spare part: HP hoses ready made for the touchfree, belts that drive my trolley and wash arm, motor brake for wash arm rotate, proxes, ultrasonic sensor, chemical injectors, treadle pads, validator for the cashier, etc.
As a rule, a critical part fails just before or during a bangin' Saturday.
Good luck!