72 BULLETIN 801, TJ. S. DEPARTMENT OF AGRICULTURE. 
arrangement is of value in conserving the water supply and pressure, 
sure, 
Fire pumps include three preferred types — the duplex Underwrit- 
er's steam pump, the centrifugal pump (usually electrically driven), 
and the rotary pump (usually mechanically driven). The available 
power often determines the type of pump used. If it is practicable 
to keep up constant steam pressure, the steam pump should be used, 
while if steam is not available throughout the season the steam pump 
should be supplemented by an electrically-driven centrifugal pump, 
usually of the double-stage type. The rotary pump meets such con- 
ditions as are furnished by water power as the available drive. Gen- 
erally speaking, the steam power is the most reliable. If electric 
power is relied on entirely there should be two supplies of current 
if possible. Pumps should deliver water at 100 pounds pressure, 
All pumps should be kept in the best condition and run for a few 
minutes every week. Main valves should be kept open and suction 
lines and intake strainer kept clean. 
Gravity tanks are usually of steel, as it makes a durable tank which 
is economical for most conditions. If a natural elevation of the 
ground can be used so as to reduce the height of the tower, tanks 
of reinforced concrete are excellent, the economy of this type of 
tank depending largely upon the local cost of the materials and 
whether or not other concrete work is being done at the time. The 
capacity of the tank should not be stinted as a large supply is very 
desirable. Moreover, the cost of the tank should be less in propor- 
tion as the capacity increases. Again, the extra capacity may per- 
mit a future extension of the plant without the necessity of an 
additional tank. Wooden tanks are sometimes used but their lia- 
bility to decay makes their use inadvisable for most conditions. 
Gauges for registering the amount of water in the tank always should 
be supplied. 
Freezing of water in tanks and risers during winter must be 
guarded against. For the greater part of the cotton belt the only 
precaution necessary is that the tank riser pipe be insulated. A 
wooden boxing packed with dry sawdust and made water-tight 
frequently will be found sufficient. Colder climates demand that 
the water be kept heated slightly during cold weather. This is 
accomplished by means of a special tank heater arranged and con- 
nected so that there is a constant circulation and even heating of 
this water in both tank and riser. Heat may be supplied by either 
steam or an independent hot -water heater. There are a number of 
different makes of tank heaters on the market. 
The amount of water supply for the private system has not been 
stated^ because this is really a matter of judgment and should be 
