88 



SMALL WATER SUPPLIES. 



(see remarks in previous chapter on friction of bends) ; 

 as before advised foot-valves on the suction are 

 essential. The suction pipe should be twice as large 

 (not twice the diameter, which means four times as 

 large) as the delivery, and more on high-speed pumps 

 if the makers recommend it. A strainer at the foot 

 of the suction pipe usually completes it. 



Ait 

 Outlpt 



FIG. 76 



Regarding the delivery pipes, it is essential to see 

 that they are truly cylindrical. For small sizes where 

 the water is not likely to unduly corrode them, 

 wrought-iron pipe (gun-barrel) with screwed collar 

 joints, etc., are used. They are, length for length, 

 about 25 per cent lighter than cast-iron pipes of the 

 same diameter, and they can be bent conveniently. 



In most cases, however, it will be preferable to use 

 cast-iron pipes, which are not so liable to corrosion, 



