62 
BULLETIN 462, U. S. DEPARTMENT OE AGRICULTURE. 
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 . 
10 
30 
100 
250 
300 
450 
600 
1,000 
1 
2 
3 
4 
5 
6 
7 
8 
1,500 
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. 
