62 BULLETIN 462, U. S. DEPARTMENT OF AGBICTJLTUBE. 



In conclusion, it has been seen that iron pipe is used in most dis- 

 tributing systems in Florida, but that this is often subject to rapid 

 rusting. It is also expensive if large sizes are used, and if small sizes 

 are used the plant is apt to be inefficient. It is not possible to avoid 

 the use of iron or steel pipe for most of the spray systems, but the use 

 of galvanized steel or galvanized iron pipe is advised for all overhead 

 lines. If a low-pressure system is used for surface irrigation, it is 

 practically necessary to have a high-pressure main pipe connect the 

 pumping plant to the relief stand. This may be either cast-iron, 

 wrought -iron, steel, or riveted steel pipe (black or galvanized). The 

 cost, of such pipe varies greatly, the cast-iron type being the most ex- 

 pensive but the most, durable for Florida conditions. The riveted- 

 steel pipe is cheapest, and will serve for a longtime if well galvanized. 

 It is probably unwise to install the asphalted or black riveted steel, 

 as Florida conditions are very hard on such pipe. 



A great deal of pipe has been taken up which has rusted out en- 

 tirely in a few years. One experienced man reports that the lasting 

 qualities of cast-iron, wrought-iron. and steel pipe are about in the 

 ratio of five to three to one. 



The size of the main will depend upon its length and the quantity 

 of water it must- deliver per minute. Most of the pumping plants in 

 Florida will not need a main of more than 1.000 feet. For such con- 

 ditions it would be well to keep within the following pipe sizes: 



Table 5. — Size of pipe required according to quantity of icater to be delivered. 



Capacity gallons per minute . . 



Size of pipe inches . . 



100 

 3 



250 



4 



300 



450 

 6 



600 



1,000 1,500 

 8 10 



If smaller sizes are used for the corresponding capacities it will be 

 necessary to increase the horsepower very materially to deliver the 

 required quantity of water. 



Finally, it will be seen that the saving effected by the installation 

 of low-pressure pipe for furrow irrigation means not only a great 

 saving in the distribution system but also a saving in the pumping 

 outfit, on account of the reduced friction in the pipe system. If the 

 power is not increased to compensate for the smaller pipe systems, the 

 result is a diminution of the quantity of water to be delivered and a 

 corresponding interference with the whole purpose of erecting and 

 operating the irrigation plant, which is. of course, the delivery of 

 sufficient water to prevent loss from the lack of moisture in the soil. 



