TERM-WATER-INGRESS
Water Ingress
Water & Fuel
Also: water contamination · free water · dissolved water · emulsified water · moisture ingress
Canonical Definition
The entry of free water or emulsified water into a fuel, hydraulic, or lubrication system. Water ingress occurs through condensation in vented reservoirs, breather contamination, seal degradation, heat exchanger failure, and improper maintenance procedures. Water concentrations above 200 ppm in hydraulic fluid cause cavitation, accelerate bearing corrosion, reduce film strength, and enable microbial growth. In diesel fuel, water above 200 ppm causes injector stiction, corrosion, and microbial contamination. Measured by Karl Fischer titration per ASTM D6304 or ISO 12937.
Engineering Context
Water is the most damaging non-particulate contaminant in hydraulic and fuel systems. As little as 0.1% free water reduces bearing fatigue life by 90% in rolling element bearings due to hydrogen embrittlement of bearing steel at asperity contacts. Reservoir breathers with desiccant or membrane barriers prevent condensation-driven water ingress in static systems. Coalescing water-separation filters are the primary active removal method.
Applicable Standards
Related Technologies
Protection Systems
Knowledge Center Articles
KC-00 Governance Metadata
| Permanent ID | TERM-WATER-INGRESS |
| Category | Water & Fuel |
| Status | Published |
| Version | 1.0 |
| Last Reviewed | 2026-07-05 |