18 



BULLETIN 57, U. S. DEPARTMENT OF AGEICULTURE. 



pounds, when it is insufficient to deliver the remaining water 20 

 feet high. It will also be found that when air is compressed in the 

 same tank with water, the water gradually absorbs the air, thus 

 making constant renewal of the air necessary. Both of the above 

 troubles are overcome by compressing excess aii' in with the water 

 until the pressure gauge again registers 25 pounds, if the tank is half 

 full of Avater. Excess air pressure may be secured by an air intake 

 valve in the suction pipe, controlled by hand, by a combination of 

 air and water pump, or byuse of an air compressor when power is used. 



=^s=m 



— TO 

 PLUMB7NO 

 SrSTEM 





Fig. lo. — Pneumatic tank supply system with tanlj: in basement supplied by windmill deep-well 



pmaping outfit. 



The following table gives the pressures in the tank necessary to 

 force water to certain heights in the house: 



Feet head of water and equivalent 'pressure in tank. 



Elevation. 



Pressure 

 in tank. 



Elevation. 



Pressure 

 in tank. 



Elevation. 



Pressure 

 in tank. 



Feet. 



Pounds. 



Feet. 



Pounds. 



Feet. 



Pounds. 



1 



0.43 



20 



8.66 



75 



32.48 



2 



.87 



25 



10.83 



80 



34.65 



3 



1.30 



30 



12.99 



86 



36.81 



4 



1.73 



35 



15. 16 



90 



38.98 



5 



2.17 



40 



17.32 



95 



41.14 



6 



2.60 



45 



19.49 



100 



43.31 



7 



3.03 



50 



21.55 



110 



47.64 



8 



3.40 



55 



23.82 



120 



51.97 



9 



3.90 



60 



25.99 



130 



66.30 



10 



4.33 



65 



28.15 



140 



60.63 



16 



0.50 



70 



30. 32 



150 



64.96 



