Tables have been prepared by Weston, Williams and Hazen, and others, showing the loss of head for all standard sizes of pipes and covering a wide range in discharge.

From the above formula the following relationship may be found:

The loss of head (h) varies directly with the square of the discharge (Q).

The loss of head (h) varies inversely with the fifth power of the diameter (d).
The discharge (Q) varies directly with the five halves power of the diameter.

The discharge varies inversely as the square root of the length (1) and directly as the square root of the loss of head (h).

33. Head Lost in Elbows, Tees, Valves, Etc.-Besides the head lost in friction in straight pipe due to the flow of water, there are other losses, such as occur in elbows, tees, valves, and meters. The condition of the surface of the interior of the elbow or tee, its diameter, and radius, effect the loss of head to such an extent that no very definite rule can be made as to the amount of this form of loss of head in a pipe system. The loss may be expressed in several ways, but for convenience it is best to express it in equivalent length of pipe of same size. The following extract is from the Engineering News, issue of June 10, 1917, p. 38:

The loss of head in long turn elbows 231⁄2 to 8 in. in diameter for all flows, is about equal to that in 4 ft. of pipe of same diameter; for same sizes with short radius, the loss of head is equal to that in 9 ft. of pipe of same diameter. For tees with long radius, the equivalent is 9 ft. and with short radius 17 ft. Loss of head in 1-in. bends is about equal to 5 ft. of pipe.

In Tables 15 and 16 are given all of the available data on the loss of head in wide open valves. For data on the loss of head in valves partly open, see Bull. 105, Engr. Exp. Station, University of Illinois.

TABLE 15.-Loss OF HEAD IN GATE VALVES

(Compiled by Charles I. Corp from experiments in the hydraulic laboratory of the University of Wisconsin)

TABLE 16.-Loss OF HEAD IN GLOBE, ANGLE, AND CHECK VALVES (Compiled by Charles I. Corp from various sources, representing practically all published data obtainable)

34. Ratio of Capacities of Pipes. It is often desirable to know how many pipes of a given size are equal to one pipe of a larger size. Pipe sizes are to each other as the squares of their diameters and this relation is often erroneously used for the ratio of capacities. Table 17 gives the correct relationship based on carrying capacity, as nearly as can be stated for all rates of flow.

'pipes?

Illustrative Problem.-What diameter pipe should be used to supply six 1-in., four 4-in., and eight 12-in.

That is, ten 1-in. pipes are equivalent to one 232-in. pipe. Where the total number of equivalent pipes does not exactly equal one large pipe, i.e., suppose the above total had been 13 instead of ten 1-in. pipes, we should use a 3-in. pipe as it is the next larger size that could be used. It is not necessary to always use 1 in. for a common base. If 14-in. pipe had been used, we would have 5-14-in. pipes; 4.8-14-in. pipes 1-24-in. pipe, giving the same result.

35. Fire Streams.-In Table 18 are given data upon such fire streams as should be used from standpipe service within a building. These streams are intended only for first-aid stream in non-fireproof buildings or for small fires in fireproof buildings. For all non-fireproof buildings, equipment should be provided to supply fire streams outside of buildings and from hydrants on city or private mains. Data for such streams are given in Table 19.

TABLE 18.-FIRE STREAM DATA FOR STANDPIPE SERVICE

34-in. nozzle, 100 ft. of 212-in. 1-in. nozzle, 100 ft. of 24-in. 1%-in. nozzle, 100 ft. of 21⁄2-in. hose

hose

hose

36. Sprinkler Systems.-The dry pipe system is one in which water is turned into the main pipes that supply the pipes in the building, but an air pressure greater than the water pressure is maintained in the distributing pipes. When a sprinkler is open, the air in the pipe system immediately begins to escape. The air pressure is thus lowered and water automatically flows into the system and escapes through the open sprinklers. The dry system is desirable only in places where wet pipes will freeze. The general Underwriter's requirements for proper installation of sprinkler systems call for the use of two independent water supplies, in order to secure the minimum rate of insurance, which may be from 30 to 50% reduction on the total insurance rates. One of these supplies must be automatic and one should furnish water under heavy pressure. The Underwriter's accept the following combination:

Public Water Works and Duplex Steam Pump.
Public Water Works and Air Pressure Tanks.
Elevated Gravity Tank and Duplex Steam Pumps.
Public Water Works and Elevated Gravity Tank.
Public Water Works and Rotary Pumps.

Elevated Gravity Tank and Air Pressure Tank.
Elevated Gravity Tank and Rotary Pumps.

A steam pressure of not less than 50 lb. should be maintained at all times on the pumps, and an automatic regulator should be applied to the steam pump so that it will start automatically when a sprinkler is unsealed, thereby furnishing the system with a full supply of water.

TABLE 20.-Loss OF HEAD IN 211⁄2-IN. FIRE HOSE
Hydrant pressure 100 lb. (from S. A. Charles)

Number of Automatic Sprinkler Nozzles, Underwriter's Rules.-The approximate number of sprinkler nozzles for open joist construction is one to every 80 sq. ft. of floor space; for fireproof construction, one to 90 to 100 sq. ft. of floor space. Nozzles are usually spaced 8 to 12 ft. apart on the pipe line and the lines 10 to 12 ft. apart, depending on the size of the bays made by the joists and floor beams.

Pressure. The supply should give not less than 25 lb. static pressure at the highest line of sprinklers and 10 lb. dynamic pressure when the section is liable to be open at one time. Tanks, Gravity.-Capacity, 30,000 gal., 75 ft. from yard level with bottom at least 20 ft. above highest sprinkler.

The Granell metal disc discharges 10% less, the Walworth 10% more and the Esty 20% more water than the above. The discharge of these sprinklers is about a mean between open 38-in. and 12-in. straight nozzle.

37. Standpipe and Hose Systems-Number of Standpipes.-There shall be one large standpipe for 22-in. hose to each accessible floor area not exceeding 150 × 75 ft.; for 114-in. and 12-in. first aid hose streams, one to each 80 × 40 ft. of accessible floor area. First aid hose lines must reach within 5 ft. of all portions of the building, and 21⁄2-in. hose streams within 10 ft. of all portions of the building. 22-in. hose should have 1-in. nozzles; and 12-in. hose, - to 4-in. nozzles.

Tanks.-Gravity tanks should have a capacity of 2500 gal. with bottom 20 ft. above roof; pressure tanks same as for sprinkler systems.

TABLE 21.-AREA, DIMENSIONS, AND CONTENTS OF WROUGHT-IRON PIPES

SIZES OF STANDPIPES FOR 22-IN. HOSE AND 1%-IN. STREAM

38. Rain Leaders or Down Spouts.-No very definite rules can be laid down for the runoff from roofs or the size of rain leaders, for the reason that there are so many modifying conditions that cannot be previously judged or estimated. The entrance to the down spout or leader may be well designed but at the time of an unusual storm would be clogged with leaves and other debris. However, if we assume favorable conditions to exist, and that the head of water maintained by the rain over the inlet to the down spout is used to overcome the resistance at the inlet and to produce the velocity in the leader at its starting point, then the relationships between intensity of rain, areas of roofs, and sizes of down spouts are given in Table 22.

This table is prepared on the assumption that the flooding of the inlet of rain leader is 1⁄2 in., 34 in., and 1 in. for small (S), medium (M), and large (L) roofs, respectively Intensity of rainfall for a few minutes, as 15, may reach 3.5 in. in Eastern and Central United States. These values for intensity of 2 in. per hour agree well with the following approximate rule: