Mechanical device which unites discrete droplets of one phase prior to being separated from a second phase. Can be accomplished only when both phases are immiscible. Requires a tight medium which is preferentially wettable and, by its nature of being tight, is also a good filtering material. Good coalescing permits gravity separation of the discontinuous phase. Coalescing may be accomplished by only a coalescer cartridge when the specific gravities of the two phases are widely separated. As the gravities' difference becomes less, the two stage principle is generally required where finely coalesced discontinuous droplets are repelled by the second stage separator cartridges.

a filter that takes the water out of fuel and does not take out any sediment

A mechanical device which unites discreet droplets of one phase of one phase prior to being separated from a second phase. Can be accomplished only when both phases are immiscible. Requires a tight media which is preferentially wettable and, by its nature of being tight, the filter is also a good filtering material. Good coalescing may only be accomplished by a coalescer cartridge when the specific gravities of the two phases are widely separate. As the gravities' difference becomes less, the two stage principle is generally required where finely coalesced discontinuous droplets are repelled by the second stage separator cartridges.