SANITATION 



53 



would inevitably prove the ruin of fireclay or stone-ware pipes. 

 Drain pipes are made in 6 feet effective lengths (i.e., exclusive of 

 the depth of socket), and also in 9 feet lengths. 



Cast-iron waste, soil and drain pipes after being cleaned from all 

 sand and rust are usually coated inside and out with Dr. Angus 

 Smith's solution, a well-known preventive against corrosion. The 

 pipes are dipped vertically into a mixture of coal tar, pitch and 

 oil, heated to a temperature of 400 F. After remaining long 

 enough to acquire the necessary temperature and to ensure the 

 thorough penetration of the solution into the pores of the metal, 

 they are withdrawn and allowed to cool gradually. Soil pipes are 

 sometimes galvanised, and both soil and drain pipes are often glass- 

 enamelled, a process which imparts a perfectly smooth glazed 

 surface to the interior of the pipe. 



Pipe Connections. As the object of a good drainage system is 



FIG. 13. An Inspection Bend 

 FIG. 12. A Bend. with bolted cover. 



to convey sewage to the sewer or cesspool as expeditiously as pos- 

 sible and with the minimum of checks on the way, lengths of piping 

 must be laid in as straight a line as possible. Bends in the course 

 naturally check to a certain extent the even flow of liquids, but they 

 are often necessary and unavoidable. Special curved pipes called 

 Bends are used when abrupt deviations from the straight are neces- 

 sary, and by the use of these specially constructed pipes the flow 

 is checked as little as possible. Sharp curves must not be made by 

 joining up small lengths of straight pipes as not only is the flow 

 seriously checked, with consequent sedimentation, but joints so 

 made are of necessity imperfect. As it is at curves that chokage is 

 liable to occur through the holding up of rubbish which should 

 not have entered the drain, curved pipes are provided with remov- 

 able hand hole lids and inspection shafts fitted with a manhole 

 cover to give access from the ground level. 



Junctions. Where one pipe joins another the junction must be 

 effected so that the inflow of sewage runs smoothly into the main 



