If a water-supply is to be installed for any house, the possibility of providing mains of sufficient size for adequate fire protection should always be considered, although it may not be found to be a necessary expenditure. In case of a fire a large amount of water is needed for a few hours, entirely negligible if it is computed as an average for the year, but a controlling factor in determining the size of mains or the amount of storage. A good-sized fire stream delivers about 150 gallons per minute, and for a house in flames, four streams are none too many. The rate of delivery, therefore, for a fire should be at least 600 gallons per minute or a rate of nearly a million gallons per day, and if it is assumed that the fire might burn an hour before being extinguished, 36,000 gallons of water would be used. If a spring or tank is the source of supply, the storage should be 36,000 gallons, and the pipe line from the tank to the hydrants must be large enough to freely deliver water at the rate of 600 gallons per minute. If the distance is not over 500 feet, a four-inch pipe is sufficiently large; but if the distance involved (from the reservoir or tank to the farthest hydrant) is more than about 500 feet, four-inch pipe is not large enough. This is because the friction in a large line of pipe is so great that the water cannot get through in the desired quantity. A four-inch pipe, discharging 600 gallons a minute, would need a fall of one foot in every four feet, while a six-inch pipe would need a fall of only one in thirty. Of course, if the reservoir from which the water comes is at such an elevation that the greater fall is obtainable, the smaller pipe may be used. It is more than likely, though, that the reservoir is about 3000 feet or more away, and the entire fall available only about thirty feet or one foot in one hundred. Then an eight-inch pipe would have to be used. Whether fire-protection piping, therefore, is a wise investment or not, depends largely on the cost of installation. A four-inch cast-iron pipe laid will cost about forty cents per running foot, while an inch pipe, large enough for everything except fires, will cost about ten cents, so that the excess cost per foot for the sake of fire protection is thirty cents, for a distance up to 500 feet (when the grade is 1 to 4) or $150. If the grade is not 1 to 4, then the pipe must be six-inch, and the excess cost is fifty cents or the cost for 500 feet will be $250. If the distance is greater than 500 and the fall not great, so that an eight-inch pipe has to be used, the excess cost is sixty-five cents a foot, or $650 for a 1000-foot line.