In cities and towns having a system of sewers, or where there is a large stream of running water near by, the matter is a simple one. In the first case, the house drain is merely extended to the sewer, into which it should discharge at as high a point as possible, and at an acute angle with the direction of flow. When the drain connects with a stream it should be carried out some distance from the shore and discharge under water, an opening for ventilation being provided at the bank. Where there are neither sewers nor streams, the cesspool must be used. When the soil is sufficiently porous the method shown in Fig. 63 may be employed. Sometimes the sewage is collected in a closed cistern and discharged periodically through a flush tank into a series of small tiles laid to a gentle grade, from 8 to 12 inches below the surface. By extending these tiles over a sufficient area and allowing from 40 to 70 feet of tile for each person, a complete absorption of the sewage takes place by the action of the atmosphere and the roots.