Filter with uniformly graded aggregate

A well uniformly graded aggregate should be used in filter because the water does not accumulate if voids are large and the base drain freely by the rising of capillary water is not possible. This issue recommends graded aggregate to close the maximum voids and make the filter very efficient. When it is exposed to running water if the gradation is not fine the filtration process will effect by ticking off the aggregates due lack of interlocking surface bonding between them in large particles. If non-uniform graded aggregate is provided, some particles will be allowed to go through and some of the particle will be held within it. Where the filter particles are small, the filter becomes plugged,  and where the filter particles are large, particles which are to be caught are allowed. The size of the voids should be such that it should be smaller than the filter particles and also smaller than the particles to be held back. But the voids should be large and permissible such that the water should be flowed easily. This technique is used and filter is formed layer by layer where the voids are narrowed down and only water is allowed through.