88 BULLETIN 414, U. S. DEPARTMENT OF AGRICULTURE. 
usually will be necessary to provide a special hot-water heater and a 
hot-water storage tank or boiler. In purchasing the water heater it 
is important that it shall provide sufficient area of heating surface in 
contact with the water to raise the temperature of the required amount 
of water to a proper point in a given time. The area necessary 
will depend on the nature of the fuel. If wood is to be used, the 
surface area of the jacket, water back, or tubes should be about 
50 per cent greater than if coal is to be burned. By " forcing the 
fire" it is possible to increase the rate of heating, but this practice 
results in the premature burning out of the heater. As an aid in cal- 
culating the necessary heating surface the following, based on the 
use of coal as fuel, may be used: 
The average size of water back having about 110 square inches, or about two-thirds 
square foot, of exposed surface, will heat to the ordinary temperature of domestic hot 
water, 180° F., about 21 gallons of water an hour. It will heat about 17 gallons of 
water to the boiling point with an ordinary fire. With a fire such as is used for roast- 
ing, washing, or baking, a water back of this same size will heat about 23 gallons of 
water to the boiling point, or 27 gallons to the temperature of 180° F. Wrought-iron 
pipe-heating coils will heat from 30 to 40 gallons of water under the same conditions. 1 
When wood fuel is used, the above performances should be reduced 
one-third. It must be borne in mind that the temperature required 
for bathing is only about 100° F., and therefore it is not necessary 
to heat the entire quantity of water which is to be used to 180° F. 
On the contrary, with the temperature of the cold water at 60° F., 
only one- third of the water necessary for bathing need be heated to 
180° F. to give a temperature of 100° in the mixed water as it comes 
from the showers. 
To act as a reservoir of hot water a tank of from 50 to 100 gallons 
capacity should be coupled to the heater. By heating the water 
capacity of such tank before the bathing of the force is begun it is 
possible to reduce the rate at which the heater will be required to 
heat water, and thus decrease its size. 
Steel tanks are most satisfactory for camp use, and they should 
be galvanized inside and out, particularly inside. Ordinarily, they 
are tested to withstand a pressure of 150 pounds, and extra heavy 
ones 250 pounds per square inch. The latter should be used when 
the gauge pressure at the tank is more than 40 pounds per square inch. 
NOTES ON FIXTURES AND APPLIANCES. 
The most suitable form of shower-bath fixture is a nickel-plated 
spray head 3 inches in diameter which may be obtained at a cost of 
approximately 25 cents. 
1 Cosgrove, J. J., in Kidder's "Architects' and Builders' Pocket Book." 
