CONSTRUCTION AND FIKE PROTECTION OF COTTON WAREHOUSES. 69 
The effectiveness of the sprinkler system depends largely upon the 
immediate availability of water under adequate pressure. A sprinkler 
supplied with water at 10 pounds pressure will discharge about 20 
gallons of water per minute, while with the pressure at 60 pounds 
the head will discharge nearly 50 gallons per minute and distribute 
the water better. The pressure adopted should be governed by the 
resulting pressure under flow considered with the cost under the 
given conditions. For example, gravity tanks, generally used as a 
primary supply, should have such elevation that the bottom of the 
tank will be at least 30 feet above the highest sprinkler head. This 
subject is discussed further under the head of " water supply." 
The automatic alarm service which the sprinkler system affords 
is a most valuable feature. These alarm gongs may be controlled 
in order that the supply line may be run through them, but this arrangement 
should be avoided if possible. 
All pipe lines should be supported securely and in such manner as to secure 
a permanent grade for drainage of the system. Sprinkler heads always should 
be turned up. 
In the arrangement of piping and heads for reinforced concrete buildings of 
several stories there will be found frequently a great advantage in the use of a 
" flat-slab " system of construction in that fewer sprinkler heads may be re- 
quired or a reduction in story height may be permissible. In any type of con- 
struction a slight increase in cost of the building, due to spacing or arrange- 
ment of beams, etc., may be more than justified by a saving in cost of sprinkler 
equipment. Therefore, it is well to plan always for the possible use of sprinkler 
equipment even though it can not be installed immediately. 
It is of primary importance that there be a proper arrangement of supply 
lines and control valves. It is essential that the control valve be so located 
as to be accessible during fire for conditions may arise making it desirable to 
cut off the supply of a section, as, for example, if the roof of one compartment 
collapsed; otherwise the water supply and pressure may be dissipated to such 
an extent as to impair the operation of the whole system. Therefore, it is de- 
sirable that each compartment system be controlled by a post indicator gate 
valve (a valve which registers whether open or closed) located if possible 40 
feet or more from the building. There should be no valve inside the com- 
partment as they may be closed inadvertently. In the case of a dry pipe sys- 
tem one dry valve may be used; for the equivalent to five single-story com- 
partments each 50 feet by 100 feet. In such case it is desirable that the dry 
valve be located 50 feet from the building, with the supply from the dry valve 
controlled by a post indicator valve. On the discharge side of the dry valve, 
and beyond the dry-valve by-pass, mains should be taken off to each com- 
partment, each main controlled by a separate gate valve, preferably of the out- 
side screw and yoke type. These valves, with the exception of the post indicator 
supply valve, should be located, preferably, in the pit with the dry valve. 
Some plants provide the dry valve near or inside of a compartment, thus af- 
fecting a considerable saving in piping. Such an arrangement is satisfactory, 
but is not so good as that previously described. 
When the dry valve is used, it should be placed in a frost-proof pit under- 
ground or in an insulated frost-proof room. It is an easy matter to prevent 
freezing of the valve at locations in the cotton belt, but farther north a small 
amount of heat must be provided. 
