Sediment filters are needed when the water supply is cloudy or turbid. The particles in the water will block plumbing systems, leave unsightly staining, may contain toxic chemicals or bacteria. The easiest way to remove the particles is by passing the water through a media where the particles get stuck and allowing clear water to flow through. The particles can be periodically ‘backwashed’ away to drain. There are different types of media which all have different advantages. Sand was the most common media but has now been superceeded by more modern variations such as Turbidex and AFM.