Trace the path from source to collection

Use the highest or earliest fresh wet boundary in the available safe observations, including changes after weather or operating-state transitions. A narrow trail that broadens below a joint can support one source hypothesis. Fluid moved by airflow may travel differently from ordinary runoff, and a stain can persist long after the original source stopped. Distinguish present wetness from accumulated historical residue.

Consider more than one source

A maintenance spill, external contamination and a genuine component leak can overlap. The appearance of the liquid may not identify its chemistry reliably. Ask whether the service team needs an approved sample or controlled cleaning to distinguish possibilities before changing parts. Do not loosen fittings, operate equipment to provoke the leak or search by touch. Pressure and other stored energy require equipment-specific qualified controls.

If the highest visible wet point lies behind a cover, the current evidence may localize a region without identifying a precise part. State that boundary honestly and let qualified examination resolve it, instead of using the wettest accessible fitting as a convenient assumed source.

Choose an inspection that discriminates

The next request should state which source regions remain plausible and what evidence would distinguish them. A replacement of the visibly wet component can fail to solve a leak originating elsewhere. If a source is confirmed, assess both the escape point and any surfaces the fluid contacted. No allowable MARSTON leakage rate or generic seal repair is supplied here; the actual component and fluid instructions govern the disposition.