Taking the plate separator a little further is the coalescing filter. These are generally comprised of hundreds of closely placed elements that force the compressed air to flow through restrictive gaps in the stack. Like the plate separator, the water separates when it comes in contact with the elements, except that with the coalescing filter this separation is considerably more efficient.

The most effective coalescing filter is the micro grid . These units are similar to plate separators, except the plates are spaced very close to one another. Close enough that micro quantities of water will wet the plate surfaces and be separated. These types of filters are fairly effective, but have the drawback of being rather expensive to purchase and fragile in operation. They are susceptible to oil contamination and generally require teardown and cleaning on a regular basis.