Coalescing and Water Separation


The image above shows the progression of the product stream through a coalescer media. The emulsion is broken apart, filtering the solids, then forcing the minute water particles to coalesce (to consolidate or join up) into larger droplets. Gravity pulls the larger droplets to the bottom of the filter housing allowing it to be drained off during filtration. This is the first of two phases.

The second phase involves separation. A Teflon coated water separation filter is used to repel any fine droplets of water that happen to pass through the coalescer. This second stage acts as a secondary back-up forcing the water out of the product flow – not allowing it to pass through with the fuel. It works because Teflon is hydrophobic (literally, fear of water). The water repels off of the coated separator and falls down to the bottom of the filter housing.


Coalescer filters are designed to filter solids and separate two immiscible liquids (liquids that do not form a homogenous mixture – do not mix well). In this case, separating water from fuel. Dixon coalescing filters are made of several filtration layers designed to remove dirt particles prior to coalescence, thereby increasing filter life. Inner and outer layers are made of fiberglass impregnated with phenolic resin for added strength and bonding. Situated between these layers is a coalescing layer made of borosilicate microglass. Coalescer filters are commonly used in two stages along with a water separator to remove free and emulsified water from fuel and various types of oil.


In order to prevent carryover of small water particles pushed through during coalescence, a second filtration stage is used to ensure water removal. The separator is a cartridge placed between the coalescer and the outlet. The screen on the separator is a hydrophobic Teflon coated woven synthetic material which can be cleaned periodically.

Dixon’s new filtration products include coalescing and water separation.  Give us a all at 1-800-874-8976 or email at  You can also check out our online store to order filtration suppliers or find out more.