Tanks.
A large proportion of the water-supply of a Municipality is usually taken from tanks, into most of which the drainage water from the neighbouring vicinity is washed during the rainy season. This can be prevented by raising the banks. The sullage water of a bazaar is indescribably filthy, and if in-drainage is prevented the tanks will fill up by percolation as the level of the subsoil water rises—a bad enough source of supply, but infinitely purer than the surface water combined with filth from a crowded area. The excavation of new tanks in a Municipality should be discouraged as much as possible, and attention paid to conserving the existing ones. Small pumps and masonry platforms for washing purposes draining away from the tanks will improve matters. In the late Mr. A. E. Silk’s book on “Municipal Engineering in Bengal” the following classification of comparative purity of water-supply is adopted:—
1. Deep spring water.
2. Subterranean or deep well water.
3. Upland surface water.
4. Subsoil water. (If distant from any collection of houses).
5. Land springs.
6. River water.
7. Surface water from cultivated land.
8. Subsoil water under villages or towns.