Also known as "sand separators", centrifugal filters are primarily for removing particulates, such as sand, from the water. They are great for situations where a lot of sand is present in the water as they don't clog up nearly as quickly as other types of filters. The dirty water enters the filter where it is swirled around the inside of a cylinder. The centrifugal force causes the sand particles to move to the outside edge of the cylinder where they gradually slide down the side to a holding tank at the bottom. Centrifugal filters are reasonably inexpensive, very simple, and are very effective for removing sand from water. Because many wells pump sand up along with the water you will often see a centrifugal filter installed on a large well. Some centrifugal filters are designed to be installed inside the well. These typically are attached to the bottom of a submersible pump. It is not unusual for a very small amount of sand to pass through a centrifugal filter. For drip irrigation systems I always add a "backup" screen filter when using a centrifugal filter as a safety precaution. A centrifugal filter used in combination with a media filter after it is an excellent combination. The centrifugal pulls out the sand, the media filter then removes the organics. This combination is very often used in municipal water treatment, where a third activated charcoal filter may be added to remove chemicals. Note that the centrifugal filter selection must be carefully matched against the system GPM or the filter will not work correctly. Always consult the manufacturer's sizing guidelines when designing a centrifugal filtration system for your irrigation system.