86 



HEALTH AND DISEASE 



drains must be ventilated by means of a grated opening a little above the 

 surface of the ground (for preference near the intercepting chamber), and 

 by a 3^- or 4-inch stout pipe of lead or cast-iron fixed to the wall of the 

 building at the highest point of the drain and carried up to such a height 

 and in such a position as to afford a safe outlet for foul air. 



Stoneware pipes jointed with Portland cement and laid on a bed of 

 concrete are commonly used for drains, but cast-iron pipes are more 

 durable and more permanently water-tight. 



In the next illustration (fig. 476) a very good method of draining by 

 the use of underground pipes, where that system is already in use or is 

 at any rate determined upon, is shown. 



Fig. 476. — Underground Drain for Stable 



In this drawing A, A represent the walls of the stable, B, B the stable 

 drain-pipe starting from the manhole G outside one end of the stable, and 

 running under the stable to the manhole at the other end in which the 

 siphon-trap c is placed. Into this drain the gullies f, f, inside the stable, 

 discharge. The siphon contains water the level of which is shown by 

 the interrupted lines. In theory at least the water is a barrier against the 

 passage of foul air from the outlet drain D back into the stable pipe, as 

 such air will take its course through the clear opening of the ventilating 

 pipe e rather than attempt to force the guarded part of the siphon c, which 

 protects the stable pipe. As will be seen in this drawing, the drain is 

 ventilated through pipes passing into the manholes at either end. These 

 manholes are covered with air-tight iron covers, and provision is made for 

 easy access for the purpose of cleaning out the drain by means of a brush 

 with jointed cane handle. A trap similar to c must be placed between 

 the outlet drain and the sewer or cesspool. It is of course essential that 

 the gullies and the drain should be kept well flushed. Automatic flush- 



