Make a sand water filter

Use this household filter to help make water safe to drink:

1. Clean a watertight 200-litre container and disinfect it with bleaching powder. Make sure the container did not contain toxic materials.
2. Drill a hole a quarter of the way down from the top of the container for a tap. The hole should be the same size as the fitting on the tap.
3. Fit the tap to the hole and fix it in place.
4. Drill or punch many small holes in the first 35cm of a piece of flexible piping, seal the end and form it into a ring on the bottom of the container, with the holes facing downwards.
5. Connect the top of the pipe (the end with no holes) to the tap. Seal the fitting with a hose clamp or wire.
6. Place a layer of washed gravel 7cm deep on the bottom of the container over the pipe. Be careful not to crush the pipe. Cover the gravel with a fine cloth and fill the container with washed, coarse sand to about 10cm below the tap. Cover the sand with a second fine cloth.
7. Make a cover for the container, with a hole in it to pour water through. Cover the hole when not in use to stop insects entering the filter. Place a flat stone or dish under the hole to avoid disturbing the sand when water is poured in.
8. Before adding water to the filter, allow any particles in the water to settle. Flush the filter with water before first use. 

Maintenance

Make sure that the sand is always covered by water to above the level of the tap. Fill the filter daily and only remove water in small amounts. If the water level drops below the level of the tap, the filter will need to be cleaned and refilled.

After a few days of use, a green layer will grow on top of the sand. This must be left undisturbed because it helps to treat the water.

When the water flow from the tap slows down, clean the filter. Drain all the water and remove the green layer and about 1cm of sand from the top. Wash and replace the cloth on top of the sand.

After many cleanings, when more than half of the sand has been removed, replace all the sand and start again. This may be necessary once or twice a year.

Adapted from pages 92 to 99 of A community guide to environmental health by Hesperian. For more information, visit hesperian.org