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 sujQS.cient 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 biu-ning 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 boiUng 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.^ 



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 mixied 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." 



