In practice for the design of horizontal flow grit chamber the flow velocity close 0.25 to 0.3 m/sec is maintained. Such velocity will carry most of the organic matter through the channel and will tend to re-suspend any that settle but permit heavy grit to settle. Therefore, velocity in the grit chamber shall be neither too low as to cause settling of lighter organic particles nor should be so high as not to cause the settlement of entire silt and grit present in the sewage.