filter bed

American  

noun

1. a pond or tank having a false bottom covered with sand and serving to filter river or pond waters.

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filter bed British  

noun

1. a layer of sand or gravel in a tank or reservoir through which a liquid is passed so as to purify it Compare bacteria bed

2. any layer of material through which a liquid is passed so as to filter it

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Etymology

Origin of filter bed

First recorded in 1870–75

Example Sentences

This valve is opened, and the watery portion is allowed to escape into a sand filter bed.

From Scientific American Supplement, No. 447, July 26, 1884 by Various

A good filter bed should not pass more than from two to three gallons per hour for every square foot of surface, and it must therefore have a large area.

From How it Works Dealing in simple language with steam, electricity, light, heat, sound, hydraulics, optics, etc., and with their applications to apparatus in common use by Williams, Archibald