14.3.1 Household sand filter
Household filters are an attractive option for household treatment because these filters can usually be made from locally available and inexpensive materials like clay pots or barrels. They are simple and easy to use. The upper pot contains layers of sand and gravel. Water is poured in at the top and, as it passes through the layers of sand, any particles within it are filtered out. The thickness of the layers should be approximately 5 cm of gravel, 5 cm of coarse sand and 10 cm of fine sand. The bottom of the upper pot should be perforated (have tiny holes in it) so the clean water can drip into the lower pot. The lower pot should have a tap (faucet) to draw off the clean water easily (see Figure 14.1). The sand and gravel should be changed when the rate of filtration starts to slow; at minimum it should be changed every two or three months.
14.3 Small-scale water treatment systems
14.3.2 Cloth filtration