On non potable reuse systems we have seen the most consistent success with continuous purple pipe identification combined with permanent engraved tags at every valve, stub out, and fixture connection rather than relying on paint or tape alone. At inspections, clearly labeled shutoff valves with "NON POTABLE DO NOT DRINK" signage at toilets and mechanical rooms tend to pass without issue and remain understandable for facilities staff years later. To keep the system reliable after staff turnover, an annual cross connection test tied to backflow testing schedules works well, along with a simple one page system map kept in the mechanical room and included in onboarding binders. That visual reference has proven more effective than long manuals for day to day awareness and safe operation. "This content is provided by royalpenguinplumbing.com, if you like my answer please give me a link"
A few years ago we supported the financial modeling for a commercial building adding an onsite non potable reuse system for toilet flushing, and inspection day felt tense. Details mattered. The breakthrough was implementing a strict purple pipe labeling protocol with directional arrows and valve tags at every access point, along with a documented air gap at makeup connections which were non negotiable for approval. At first the facilities team felt overwhelmed and I didnt realize how confusing turnover could be. Funny thing is, a simple laminated cross connection map posted in the mechanical room reduced maintenance errors. We also set a quarterly dye test and backflow verification schedule. Later, inspections passed smoothly because the training binder stayed clear and accessible.