All coalescing oil separators use a borosilicate glass filter element, which is designed to remove small oil particles and system contaminants. Therefore, it is important to monitor pressure drop for new installations. Once the pressure differential exceeds 15 psig, it is recommended to replace the filter.

Westermeyer's coalescing oil separators use a borosilicate glass filter element designed to be 99.5% effective at removing oil particles and system contaminants above 0.3 microns in size. It is recommended that the oil separator be changed when the pressure differential exceeds 15 psig.