LAND DRAINAGE BY MEANS OF PUMPS. 43 



tractors often have underbid others who have become familiar with 

 foundation construction under such circumstances, and the former 

 have been awarded the contract. However, such bids often prove 

 to be the highest, because of delays, unsatisfactory results, and even 

 forfeiture of contract. Often the expense of foundation is a large 

 part of the cost of the completed plant. When properly constructed 

 it is the- most permanent part of the plant, and should outlast the 

 building and serve as the support for several sets of machinery. 



ARRANGEMENT OP SUCTION AND DISCHARGE PIPING. 



Proper arrangement of the suction and discharge pipes is essential 

 to the economical and reliable operation of the plant. The pipes 

 should be as direct as possible. All bends should be of long radius, 

 and the interior of the pipes should be as smooth as practicable, 

 in order that the lost work, due to friction, may be small. Since 

 the head consumed in overcoming friction varies as the square of 

 the velocity, the larger the piping the less the friction loss. The 

 piping should be made large enough to reduce the velocity in the 

 pipe to as near 5 feet per second as practicable. AH changes in size 

 and direction of the piping should be gradual, and at no point should 

 the water be permitted to flow around a sharp corner. 



The suction pit should be carried to a greater depth than the main 

 canal, even though this results in some danger of excessive seepage 

 and of opening springs or boils through the lower layers from the 

 river when the suction pit is close to the river bank. This has been 

 a frequent source of difficulty in pumping plants, and on this account 

 the discharge pipe should be made longer than it often is. The sides 

 of the suction pit should be protected by a reinforced-concrete wall 

 supported by round piling, and usually a cut-off wall of sheet piling 

 should be driven along the center lines of these side walls. If the 

 material in the bottom of the pit is inclined toward quicksand, or if 

 there are springs and boils, the bottom as well as the sides of the pit 

 should be of reinforced concrete well tied down by the use of round 

 and sheet piling, as it must be remembered that there will be an up- 

 ward pressure on the bottom of the pit when the water is lowered. 

 The pit should be shaped to form a suitable gradually-curved entrance 

 to the suction pipe, and should be provided at its outer end with a 

 steel screen. The screen openings should be of such size that the 

 velocity through them, under normal conditions, would not be more 

 than 1 foot per second. 



In order that the suction lift maybe kept low, the pump should be 

 set as low as is consistent with securing good foundation, ease of 

 installation, and safety after installation. In general, the plant 

 should be nt sur-.h ;ni elevation as would make it very unlikely that 

 excessive rainfall or suspension of pumping would cause the water 



