Water turbitity (cloudiness) is caused from particles such as sand silt clay and other trace elements in the water.
Turbidity is the cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.
A turbidity meter passes a beam of light through the water and measures the light scattered by suspended particles.
Valves can be plugged by suspended particles and incapcitate reverse osmosis membranes. Suspended particles are typically removed with filter pore sizes of 1 to 20 microns.