274 



FARM BUILDINGS IN SOUTH AFRICA 



inspection chamber which is not occupied by the channel should be well 

 benched-up in concrete and sloped towards the half-section channel, so as 

 to confine the sewage, as far as possible, to the latter, its proper course. 

 White-glazed, half- section, stoneware channel-pipes are manufactured for 

 the above purpose. 



In the case of an inspection chamber, where a tributary drain joins a 

 main drain, the invert of the tributary channel should be slightly 

 higher than that of the main channel, so that the former will discharge 

 over the latter. If branch drains enter the inspection chamber from 

 opposite sides, the branch channels should be arranged so that they do 

 not discharge (into the main channel) immediately opposite each other. 



Inspection chambers should be large enough to allow of the insertion 

 of cleaning rods or wire. The chamber shown is 18 inches square. If, 







Fig. 210. 



however, the drain lies deeply in the ground, the inspection chambers 

 should be larger. 



In the case of a large inspection chamber, there is no need to have 

 the inspection cover larger than 24" by 24" (the largest size commonly 

 stocked by merchants), because the brickwork can be corbelled inwards 

 towards the top, so as to diminish the orifice to suit the size of cover. 



An 18" by 18", cast-iron, single-seal manhole cover, such as that 



in Fig. 210, costs about 15s. 6d. in Johan- 

 nesburg. 



Cleaning Eyes. — Two types of cleaning 



s£*leo wr» s/rvMM eye are illustrated. That in Fig. 211 



consists of an oval eye in the pipe, closed 



by a stoneware lid, the joint being sealed with bitumen. This type is 



suitable when the pipes are near the surface of the ground. 



