RECIPEOCATING PUMPS 583 



i.e., the distance from supply level to level of bucket valve with the bucket 

 in its highest position should not exceed this value. 



If h d = delivery head on pump in feet, i.e., height between bucket and 



FIG. 269. Single-acting Force Pump. FIG. 270. Single-acting Plunger Pump. 



outlet, the pressure head on upper side of bucket = 7r a -\- h d feet. 

 /. Total head on bucket 



= h d + /i, = H feet, 

 where H = toiial lift .of pump. 



On the up stroke, then, water is lifted out at the top of the pump and 

 the tension of the pump rod is given by W H A Ibs., where 

 A = area of bucket in square feet. 

 W = weight of 1 cubic foot of water = 62*4 Ibs. 



(This neglects the resistance of valves and passages.) On the down 

 stroke water escapes through the valve, from the under to the upper side 

 of the bucket, so that all the work is done on the up stroke. 



By the addition of a closed top fitted with a stuffing box through which 



