Sewage from buildings is disposed of chiefly by the following methods: (1) By a connection to the street sewer; (2) by cesspools; (3) by director indirect discharge to sea, or river, in close proximity to the buildings. The first plan is always adopted in well-regulated cities, having a sewer system, and the work is usually done under the supervision of city authorities.

Cesspools are commonly used where the first and third methods cannot be employed. They should be built watertight if within 200 ft. of any buildingsor within 100 yd. of any well. Fig. 2 shows common practice in cesspool connections. The main drain from the house Is continued through the cellar wall, a trap a and fresh-air inlet b being placed outside; cither a vitrified or a cast-iron sewer pipe c connects with the cesspool d; and a cesspool vent e is run up the trunk of a tree. A tight-fitting manhole cover should be provided for access.

Disposal Of Sewage 353

Fig. 2.

The size of a cesspool must be determined by the approximate amount of discharge. The least size for a 7- or 8-room house is from 6 to 8 ft. in diameter, and from 10 to 12 ft. deep. The following rule is in common use: For a house with 6 rooms or less, make the cesspool 6 ft. in diameter; for a 7-room house, 7 ft.; increase the diameter 6 in. for each additional room up to 10 rooms; then 3 in. for each additional room up to 20; then 1 1/2 in. for each additional room. The general depth is from 10 to 15 ft. The cesspools should be brick-lined, domed over, and, if possible, provided with an overflow.