268 



FAEM BUILDINGS IN SOUTH AFRICA 



purpose of flushing the drains, and this operation should be performed 

 once or twice per week. 



No drain should be constructed under any building unless that course 

 is quite unavoidable. Should it be imperatively necessary to construct 

 such a drain, it should be laid in a straight line for the whole distance 

 under the building, and the pipes composing it should be imbedded in, 

 and covered with, good cement concrete at least 6 inches thick all round 

 the pipe, and an inspection chamber, which will permit of the insertion 

 of cleaning rods or wire, should be provided at each end of the part of the 

 drain that is under the building. 



Wherever any change of direction, or sudden fall, occurs in a drain- 

 pipe line, an inspection chamber should be constructed. 



It is desirable that an inspection chamber should be constructed 

 where any branch or tributary drain joins another drain. The tributary 

 drain should join the other obliquely in the direction of flow, and not at 

 right angles. 



In positions near buildings, where the escape of foul sewer gas would 

 be insanitary, and would tend to create a nuisance, inspection chambers 

 should be fitted with air-tight covers. 



The entrance to any drain pipe should be trapped by an intercepting 

 or gulley trap, so constructed (in the form of a U pipe) that there is 

 always a liquid seal therein, which prevents evil-smelling sewer gases 

 from entering the dwelling or stock house served by the drain. 



An ordinary square gulley trap is shown in Fig. 205. Such a gulley 

 trap can also be had round, and is suitable for the reception of bath 



Mess n, water. Gulley traps are placed 



at ground level, and have their 

 mouths surrounded by a curb 

 either of hard bricks on edge 

 rendered with cement plaster, 

 or of concrete. 



A stable gulley trap is illus- 

 trated by Fig. 206. It is pro- 

 vided with a perforated tray, 

 which intercepts solid matter and can be withdrawn at intervals for the 

 purpose of emptying it of the said solids. 



The discharge from a kitchen sink takes place, through a layer of 

 filtering grass, into a grease trap which also acts as an intercepting trap, 





Fig. 205. 



Fig. 206. 



