RO/NF Troubleshooting & Diagnostic Methodology Scope: spiral-wound thin-film-composite (TFC) polyamide RO/NF elements (8" standard + 4" variants). Numeric thresholds carry vendor + year of source. Convention markers: - — likely bug or incorrect assumption in calling code; highest priority - — enhancement opportunity (new alert, new state, refined threshold) --- §0 — Diagnostic Frame of Reference 0.1 Five orthogonal failure modes Every observed deviation must be classified into one (or more) of: 1. Fouling — reversible / partially reversible accumulation (colloidal, biological, organic, partic…