35. Cisterns are often necessary where springs are scarce and wells are not available.

A cistern should be built in much the same manner as the cesspool shown in Fig. 2, but should be larger; about 8 feet in diameter and from 6 to 8 feet deep. Cisterns are usually built of brick laid in cement and are made waterproof by covering both the inside walls and floor with an inch of pure Portland cement. The manhole should have a pump set in it.

The roof leaders are all run into an earthenware pipe connecting with the cistern, and a 4-inch outlet pipe, similar to the pipe shown in Fig. 2, is provided to carry off surplus water.

36. It is sometimes found, during excavations in shelving rock, especially if the foundations are on a sloping hillside, that a spring, or springs, are encountered, the water from which will run into the cellar. This water should never be allowed to run through open channels; but a shallow well about 3 feet deep should be made just beyond where the spring issues. A channel should then be made and a pipe laid, with tight joints, leading to a proper place of disposal. If a gravel bed is in the neighborhood, the pipe may be carried to that and emptied into a pit filled with loose stone; from which it will percolate through the gravel. If the spring water is good for drinking, the pipe may run into the cistern, should one exist.

Cisterns 4

Fig. 4.

Fig. 4 shows the arrangement: a is the spring and well; b, the pipe under the cellar bottom; c, c, the cellar walls; and d, the cellar bottom.