142 



SMALL WATER SUPPLIES. 



is now usually conducted in proper cement-jointed 

 fireclay pipes from the gullies to an underground 



chamber, either 

 circular or rect- 

 angular in plan, 

 built of brick or 

 concrete and 

 waterproofed in- 

 side. The draw- 

 ings show a rect- 

 angular one, and 

 provided with a 

 catch - pit and 

 strainer, which 

 are placed in an 



FIG. 105. 



accessible position. This will intercept and retain 

 any foreign matter, and in addition to which is a 

 gauze strainer, as shown. The tank is provided with 

 an overflow, vent pipe, and a suction pipe for con- 



FIG. 106. 



nexion to a pump. The actual size of the tank re- 

 quires calculating according to the amount of roof 

 surface which supplies water to it. If 8J cub. ft. of 

 tank capacity is allowed for etfery 100 sq. ft. of roof 



