Following the establishment by previous work in this department of the practicability of using water lubricated bearings for boiler feed pumps and similar applications, and of the suitability of various journal/bearing material combinations for use in water lubricated bearings running in clear water, this project was undertaken to determine the effects of debris in the lubricating water, such as might be encountered in practical applications. A number of material combinations were subjected to a standard test-run to obtain a comparative evaluation under extreme dirty water conditions. The best material combination, which was found to be a tungsten carbide journal with a metallized carbon bearing, was then used to determine wear rates and loading limits under various conditions. Relationships between bearing load, dirt particle size and wear rate have been established and the results lead to the recommendation that the water supply to water lubricated bearings in the boiler feed water circuit should be filtered to remove particles of debris bigger than one third of the calculated minimum film thickness, unless this latter is greater than 60 μ (about 0.0025 in), in which case filtration is unnecessary, since it has been established that very few particles greater in size than 20 μ are present in boiler feed water.