..-.is. California Agricultural Extension Service CIRCULAR 134 MARCH, 1947 m } jU J. E. CHRISTIANSEN THE COLLEGE OF AGRICULTURE UNIVERSITY OF CALIFORNIA • BERKELEY • \, "LAWN SPRINKLER SYSTEMS" is intended mainly as a guide to the home owner. However, the technical informa- tion it includes may be helpful to dealers, contractors, plumbers, and others with a professional interest in sprinkler systems. UNDERGROUND SYSTEMS, because of their convenience, are widely used in California, not only in the cities but also on farms. Many of them do not operate properly because they were incorrectly planned. For instance, when there are too many sprinkler heads on one line, and when actual water pressure at the sprinkler heads is too low, the sprinkler system will not do the job. A poorly planned system may be more of a nuisance than a convenience. BEFORE YOU SELECT and install a sprinkler system, you need to have these questions answered: What are the types of sprinkler systems? What type of system best fits the size and shape of your land? What combinations of sprinkler heads (and pipelines) meet your need? How is a sprinkler system planned? How is it installed? How is it maintained and operated? THIS CIRCULAR attempts to give you the information with which to answer these questions. It does not deal with the im- portant question of cost, except in broad comparisons between types of installations, because present-day prices are so un- certain. THE DEGREE OF YOUR SUCCESS with a sprinkler system will depend upon the care with which you plan and install it. Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914. B. H. Crocheron, Director, California Agricultural Extension Service. LAWN-SPRINKLER SYSTEMS J. E. CHRISTIANSEN 1 The simplest kind of sprinkler system is a small portable sprinkler attached to a garden hose connecting with a hydrant or hose bib. For small areas, includ- ing most home lawns, an underground system having small sprinkler heads set flush with the surface of the sod is perhaps the most satisfactory ; one need only open and close a valve to sprinkle the lawn. For areas 50 feet square, or larger, rotating sprinklers that cover up to about 100 feet in diameter are usually more economical, though they may be less convenient to operate. Pop-up sprinklers that rise above the lawn when the valve is opened — but are otherwise flush with the surface — are available for underground systems, and are extensively used for parks and cemeteries. Portable rotating sprinklers which can be attached to an automatic lawn valve installed flush with the surface of the ground are also available. One sprinkler may then be used with several valves. Lawn valves of this type often do away with the need for other hydrants in the garden, since they can be conveniently used for attaching garden hose. Sometimes used for lawns is the nozzle line consisting of a pipe (%- or 1-inch size) which lies on the ground, partly embedded in the sod. It holds small nozzles, spaced 2 or 3 feet apart, which discharge at right angles to the line. These lines can be used for covering strips 6 to 60 feet wide. Each is equipped at one end with a turning union and handle, so that the nozzles may be pointed in the desired direction. TYPES OF SPRINKLER HEADS: They are either fixed whirling, or slow-revolving, and selection depends upon the pipe system, size, and shape of area to be sprinkled Fixed sprinklers have no moving parts. Each fixed sprinkler covers the whole area it serves at once with a rather fine spray. There are several types of fixed sprinkler heads : full circle that cover circular areas, and square heads that cover areas approximately square ; half -circle heads for use along walks and other borders ; and quarter-circle heads for corners. Fixed sprinklers are extensively used in the underground, or concealed, type of sprinkler system. They are available in several sizes (for spacings varying from about 8 to 20 feet) and have capacities of 1% to 5 gallons, or more, per minute. They are designed to operate at pressures of 10 to 25 pounds per square inch. Figure 1 shows this type. A variation of the fixed sprinkler head is the pop-up lawn head, which auto- matically rises about 2 inches above the sod when the valve is opened, and falls back flush with the sod when the valve is closed. Such heads can be spaced somewhat wider than the regular heads, because they are up where the grass does not interfere with the spray. Whirling sprinklers are small to medium-sized rotating sprinklers that revolve rapidly. Most of these have two nozzles, one or both setting at an angle with the arm of the sprinkler; the reaction of the jet causes the sprinkler to 1 Assistant Irrigation Engineer, Experiment Station, resigned April 1, 1942. ri] 2 California Agricultural Extension Circular 134 rotate. Usually one nozzle (sometimes both) will be slotted, or will be equipped with some type of deflector which breaks up the jet into a spray to cover the area near the sprinkler ; the other nozzle may have a round opening so that it will cover the outside part of the circular area. These whirling sprinklers are sometimes used with lawn valves on an underground pipe distribution system, but more often are mounted on low stands attached to a hose. Slow-revolving sprinklers rotate slowly and cover relatively large areas, often more than 100 feet in diameter. The driving mechanism produces a slow rate of rotation. If reaction-drive nozzles are used, some type of vibrator is ordinarily employed to prevent the sprinkler from stopping when adjusted for slow rotation. The slow rate of rotation, preferably less than one revolution per minute, is necessary to obtain maximum coverage and to permit the widest possible spacing of sprinklers. These sprinklers are extensively used for agri- cultural systems, large parks, golf courses, and large lawns. Figure 2 shows various whirling and slow-revolving sprinklers. Rotating pop-up sprinklers are also widely used on large lawn areas. CHARACTERISTICS OF SPRINKLERS: Water pressure, spacing, and sprinkler pattern are each important to satisfactory results For satisfactory operation, sprinklers should distribute water fairly uni- formly over a specific area. To do this, a certain minimum pressure is required, below which proper distribution is impossible. When the pressure is low, the drops are large, and relatively more water is thrown to the outside edges of the area covered ; when it is high, there is a fine spray, and more water is distrib- uted near the sprinkler. In general, the larger drops fall near the outside of the area covered ; the smaller drops and spray, nearer the sprinkler. A typical example of inadequate pressure is the doughnut pattern — where very little water is deposited near the sprinkler. High pressures break up the water into finer drops, which are affected by wind to a greater extent. Variations in pressure affect some sprinklers more than others. The effective area covered is that area which corresponds to the maximum spacing for which a fairly uniform application can be obtained. Too close a spacing of sprinklers may then cause less uniformity because of excessive ^ Lawn-Sprinkler Systems 3 overlap ; too wide a spacing, inadequate coverage of the area in the center of the square between 4 adjacent sprinklers. For example, a sprinkler may ac- tually cover a circle 50 feet in diameter ; but if the application is most uniform when such sprinklers are spaced 30 feet apart, then the effective area for that sprinkler is 900 square feet. All sprinkler patterns taper off gradually to the edges of the area covered, some more so than others. The highest degree of uniformity is obtained with a cone-shaped pattern — one in which the greatest amount of water is applied at the sprinkler and tapers off uniformly to the edges of the area reached. For such patterns, the best spacing is about 50 per cent of the actual diameter covered. If patterns show a more even application for some distance out from the sprinkler, somewhat greater spacing may be used, but less uniformity is then obtained. The discharge from any sprinkler depends upon the size and shape of nozzles, or openings, and is proportional to the square root of the pressure. This means that if the pressure is doubled, the discharge of the sprinkler under the doubled pressure will be V2 times the former discharge or an in- crease of 41 per cent. If the pressure is quadrupled, the discharge will be doubled. TYPES OF SYSTEMS: An underground system with fixed heads is generally more satisfactory than rotating sprinklers, but more expensive for large lawns Underground Lawn-Sprinkler Systems. — The most common lawn- sprinkler system is an underground, or concealed, one using small fixed sprinkler heads set flush with the surface, as shown in figure 3. This type, when properly installed, is usually more satisfactory than any other, both for large areas and for small private lawns requiring only a few sprinkler heads. For large lawns, however, it is relatively more expensive than some of the other systems described in this circular. For satisfactory operation, underground lawn sprinklers should be close enough together to cover the entire area rather uniformly. The pipe sizes should be ample enough to carry the water to the sprinkler heads, and yet leave remaining a sufficient pressure to operate the sprinklers. The difference Fig. 1. — Different types of fixed sprinkler heads. The center three are lawn heads, and the two end ones are commonly called shrubbery heads. California Agricultural Extension Circular 134 Fig. 2.— Different types of rotating sprinklers. A, B, C, D, E, and F, sprinklers with external driving mechanisms : A, spinning-wheel type; B, D, and F, oscillating spring type ; C and E, pendulum type. Lawn-Sprinkler Systems Fig. 2 (Cont.). — G, H, and I, reaction-drive whirling sprinklers. J and K, reaction drive with vibrator for slow rotation. L and M , internal-drive sprin- klers : L, friction type ; and M, gear type. 6 California Agricultural Extension Circular 134 between the pressure at the main and that required at the sprinklers is the pressure that can be used to overcome friction losses in the pipe lines ; this is one of the factors governing the number of sprinklers that can be successfully operated at one time. The planning of an underground sprinkler system, including the proper spacing of the sprinklers, is discussed on page 7. Sprinkler Systems with Rotating Sprinklers. — A system with one or more rotating sprinklers is ordinarily more economical for a lawn 50 feet square, or larger. The economy in this type, as compared with the usual concealed lawn-sprinkler system, lies in reducing the amount of pipe and number of fittings required. Stationary sprinklers mounted above the surface are un- sightly and, as a rule, undesirable. However, pop-up sprinklers, or portable sprinklers attached to lawn valves, may be used. These come in various sizes. With adequate pressure, one sprinkler will cover an area up to a maximum of about 100 feet in diameter. Sprinklers with adjustable deflectors on the nozzles can be adjusted to cover the desired area. Sometimes additional concealed sprinkler heads in the corners are needed to cover areas not reached by the rotating sprinklers; or the corners may be so filled in with shrubs that the lawn can be entirely covered with one central sprinkler. For large lawns, pop-up rotating sprinklers, or lawn valves for portable sprinklers, may be spaced 50 to 80 feet apart, depending upon the size of the sprinkler and the available pressure. Fig. 3. — Underground, or concealed, lawn-sprinkler system in oper- ation. This is probably the most satisfactory type, especially for rela- tively small lawn areas. &mfr' Lawn-Sprinkler Systems 7 Nozzle Lines. — To sprinkle rectangular areas, especially narrow parking strips between the sidewalk and the curb, nozzle lines are satisfactory. On parking strips, these lines are usually placed next to the sidewalk so that the water is thrown toward the street. They are sometimes installed on the curb side, however, to eliminate noticeable waste. Short-throw deflector nozzles are used for strips less than about 8 feet wide. These nozzles are usually spaced 2 to 3 feet apart. Three-quarter-inch pipe can be used for strips up to about 100 feet long, and 1-inch pipe is recommended for strips up to about 200 feet. Choice of pipe size, of course, largely depends upon the particular nozzles used, since makes and types differ. The special hand-turning unions designed for the purpose should be used on the nozzle lines. Pipe unions having ground contact faces, though sometimes used, are not entirely satisfactory. If no turning union is provided, one can rotate the pipe by simply turning the threads in one of the connections. Handles are formed by a tee (T) and a short length of pipe with a cap on the end. The nozzles are generally installed so that the direction of the spray will line up with the handle on the turning union. When the handle is pushed down against the ground, the nozzles turn down on the side of the pipe, where they will be protected from damage by lawn mowers. Nozzle lines for covering strips 20 feet wide, or wider, are usually less satis- factory than the underground sprinkler systems. Strips of this width require nozzles that discharge the water in a straight jet. With a given setting of the line, most of the water falls in a narrow strip a certain distance from the pipe. For complete coverage of a wider strip, a nozzle line located along the middle of the strip is objectionably conspicuous. The pipe for nozzle lines can be purchased locally and drilled and tapped by hand. However, since it is difficult to get the nozzles lined up accurately, installers usually prefer to order pipe which has already been machine-drilled and tapped to insure proper alignment. HOW TO PLAN A SPRINKLER SYSTEM: There are eight points to consider, and the problem is to reduce resistance and maintain pressure These are the steps in planning an underground sprinkler system with fixed heads : a. Determine available static water pressure. b. Make a sketch of the yard. c. Select and locate control valves. d. Select and space sprinkler heads. e. Determine number of sprinkler heads on one line. f . Select sizes of pipes on the basis of friction loss in pipes and resistance of water meters, valves, and fittings. g. Install, allowing for lawn settling, h. Adjust sprinkler heads. Following is a detailed discussion of these matters ; it contains tables by which may be determined friction loss of pipe, resistance of fittings, and number of sprinkler heads for given sizes of valves and pipe. 8 California Agricultural Extension Circular 134 1. Available Static Pressure. — First determine the available static water pressure at the water main. This may be 20 to 80 pounds per square inch ; in the majority of cities, 35 to 45 pounds per square inch is most common. Static pressure can be obtained from the water department, or it can be determined by attaching a pressure gauge with a hose-thread adapter to any faucet or hydrant. This test should be made at the hour when most of the sprinkling is done in the neighborhood, because the pressure will then be at a minimum. 2. Sketch of Yard. — Make a sketch of the yard, showing the location of lawn areas, the water-supply line, and the connections for the sprinkler system. This drawing should be made to a scale of not less than % inch per foot. The system can then be completely mapped out on paper, and the correct number of fittings determined. A plan of this type is shown in figure 4. Several sprinkler manufacturers offer a free plan service. They will furnish a complete sprinkler layout showing all pipe and fittings required. The home- owner must furnish a rough sketch of the yard, showing the location and dimensions of house, walks, gardens, and water supply pipes, and a statement of the available pressure. Dealers can furnish information about this service. 3. Control Valves. — Control valves should be selected and located with par- ticular care. The ideal valve is of rugged construction, offers little resistance to flow, and does not leak when closed. Valves are usually set down in the ground, being protected by a valve box of some type, and are operated with a key. Sturdy equipment is an economical investment and the cost of replacing valves of inferior quality will exceed the additional cost of first-class ones. A union next to the control valve will make replacement easier. Special angle valves for sprinkler systems are provided with a union connection. Different types of valves are shown in figure 5. Angle valves are most satisfactory for sprinkler installations. Their resis- tance to flow is generally only about one third that of globe valves of the same size. They are reasonably watertight and are usually provided with re- placeable discs that can be renewed without removal of the valve. Angle valves often do away with the need of elbows. The principal objection to globe valves is their high resistance to flow. Gate valves, though they offer less resistance, are seldom satisfactory because of leakage, especially where there is sand in the water. They should be used in places where the valve is closed only occa- sionally, where its normal position is open, and where slight leakage may not be harmful. The location of the control valves is also important. Locations next to walks or porches, and far enough away from the nearest sprinkler heads to protect the person operating the valve from getting wet, are most desirable. Places not readily accessible or under shrubs should be avoided. Usually it is better to place several valves in the same location, rather than to scatter them, even though this arrangement requires additional pipe. 4. Capacities and Spacing of Fixed Sprinkler Heads. — Most of the fixed sprinkler heads used for underground lawn-sprinkler systems have capacities of 1% to 3 gallons per minute, under operating pressures at the sprinklers of 10 to 20 pounds per square inch. According to tests, several common sprinkler heads carried by hardware stores have capacities of 2 to 2% gallons per minute at a pressure of 15 pounds per square inch ; they will distribute the water Lawn-Sprinkler Systems . . A/a/r?6er Z eyenc/: regret/ - % a/?y/e i/a/i/e 7 O - fu// c/rc/e head ^ - ha/f c/rc/e tie ad d -aucrfer c/rc/e /?ead Sco/e - feet Fig. 4. — Design of an underground sprinkler system for a 60-foot lot. satisfactorily at this pressure, when spaced 10 to 12 feet apart. Half-circle heads for installation along walks and borders are available. They have one half to three fourths the capacity of full-circle heads, and can be installed 10 to 12 feet apart. Half -circle heads are commonly used for parking strips 6 to 10 feet wide ; they are installed along the walk and discharge toward the 10 California Agricultural Extension Circular 134 Fig. 5. — Different types of valves for small pipe lines. A, Angle valve, made espe- cially for sprinkler systems, having union connection and designed for operation with valve key ; B, regular angle valve ; C, globe valve ; D, gate valve ; and E, check valve for preventing back flow in pipes. street. Quarter-circle heads are used at corners. When used along the outside edges of a lawn, part-circle heads may be assumed to cover a strip 5 to 8 feet wide. The rest of the area can then be divided into squares, with full-circle heads installed at the center of each square. An alternative method is to locate the heads in an equilateral triangular pattern. A maximum spacing of 10 feet apart in a square pattern, or 12 feet apart in a triangular pattern, is usually recommended. Sprinkler heads that cover a square rather than a circle are available, but they have no particular advantage except around the edges and next to walks if part-circle sprinklers are omitted. 5. Number of Sprinkler Heads on One Line. — The maximum number of sprinkler heads to be installed on a line under one control valve depends upon : a) the available pressure at the main, b) the total resistance in the supply line between the main and the sprinklers, c) the capacity of the sprinkler heads, and d) the arrangement of the sprinklers, whether on a single continu- ous line or on two or more branch lines. When too many heads are installed on one line, the pressure at the sprinklers will not be adequate for proper distri- bution of water, and the coverage will be reduced. Although no harm results Lawn-Sprinkler Systems 11 from installing- fewer sprinkler heads on one line than is permissible, greater economy is obtained by arranging the sprinkler layout to require a minimum number of control valves. This means that each line with a separate control valve should carry as many sprinkler heads as possible. (See table 3.) 6. Friction Loss in Pipes. — When water flows through a pipe line, pressure is decreased in overcoming f rictional resistance. The smaller the pipe and the higher the velocity, the greater the friction loss. The resistance to the flow of a given amount of water is greater for small pipes than for large ones. Thus, TABLE 1 ■ Fric8*i©n losses in Galvanized iron Pipe* Gotlons \- : :' per Minute PIPE SIZES, IN INCHES V* % 1 VA 1% 2 Pressure loss in pottnds per square inch per 100 feet of pipe 1 0.65 2 . 2*30 0.61 mmwtwmwmm ...... 3 4.90 1.25 0.39 4.... 8*31 2.16 0.65 0.17 5 12,5 17.7 3.25 4.55 1.00 1.41 0.26 0.37 0,12 O.I 7 0,05 6 7 23.3 6,00 1.86 0.49 0.23 0.07 * ... 30,3 7, SO 2.38 0,63 0.29 0*09 9 37.2 9,55 2.96 0,78 0.36 0.11 10 45.4 11.7 16.4 3.64 5.11 0.94 1.33 0.44 0,62 0.13 0,13 12 14 21.7 6.71 1.77 0,83 0,25 16 28,0 8.66 2.25 1.05 0,32 18 -..♦.. 34.8 10.8 2.81 1.31 0,40 20 ;■;.. 42.0 13.0 3,42 1.60 0.43 25 ...... 19.7 27.7 5.14 7.31 2.42 3,33 0.72 1.01 30 ;:.... 35.... ...... 36,8 9.64 4.45 40 | ...... 47.1 12.3 5.75 1.73 45 15.3 7A^ 2.14 50 ......... . 18.7 22,4 26.4 8.74 10.4 12,2 2,62 3.10 3.65 '$$ '. .. 60 [ ...... 70 . .. ...... ■■■■■■ 1 • ! 35,0 44.5 16.3 20.8 4,87 6.23 SO *fiom WUJtera* «n<$ Moxe«'5 fo* mVto* C-ctso. 12 California Agricultural Extension Circular 134 TABU 2 Approximate Resistance of Pipe and Fittings in Terms of Equivalent Length of One-Inch Pipe" Pip© *mem§ Fittings SIZES, IN INCHES % Va VA VA Pipe, per foot . .. Enf re re«e hestst Water meters.. . ... .. GSofos V«ives. Angle volves. . ...■*.♦ Oorden hydro nts .... Oote veiv«». ..Elbows Toes,, side outlet . . . . . Seducers feme*!! sked) Equivalent length of one-lneh pipe, in feet 27 100! 2 SO 100 150 IS 10 20 15 3*2 8 50 80 25 50 3 4 6 1 3 20 30 8 15 1 2 3 3 0.25 0.12 1 10 10 5 3 2 5 3 1 1 1 1 1 1 *B«*eri <*n Williams and Hastens ferowta, C*=l ISO. .fftesitton*© ©* 5 /8'lneh meter, the smallest &Jse made* 0,037 4 2 1 1 the resistance of a %-inch pipe is about 12.5 times that of a 1-inch pipe ; or, in other words, each foot of %-inch pipe will have as much resistance as 12.5 feet of 1-inch pipe. For a given flow, resistance offered by a pipe will depend primarily upon its size and upon the roughness of its inner surface. "When a pipe corrodes on the inside, the frictional resistance is increased, both because of the increased roughness and because of a reduction in area. Table 1 gives the friction loss in pounds per square inch for streams of 1 to 80 gallons per minute in 100 feet of galvanized iron pipe of different sizes. New pipe, either black or galvanized, will have a greater capacity than indi- cated by this table — that is, for the same flow, the friction loss will be less. Some allowances have been made in the table for the inevitable increase in roughness. Since galvanized pipe will maintain its carrying capacity much longer than black pipe, it is recommended for sprinkler systems. One can readily obtain the friction loss in any length of pipe by multiply- ing the pressure loss, obtained from table 1, by the length of the line in feet, and dividing by 100. For example, what is the friction loss in 250 feet of %-inch pipe carrying 10 gallons per minute? The pressure loss, 11.7, times the length of line, 250, equals 2925.0. Divide 2925.0 by 100 and the answer is 29.3 pounds per square inch friction loss. 2 250x11.7 2925.0 100 100 = 29.3 pounds per square inch. Lawn-Sprinkler Systems 13 Copper tubing has recently come into use for sprinkler systems. It has a smooth inside surface, which corrodes slowly and will maintain a high water- carrying capacity. It is made in several grades for use with solder fittings. The lighter weights cost very little more than galvanized pipe. 7. Resistance of Water Meters, Valves, and Fittings to Flow of Water.— Besides the loss of pressure caused by the friction in a pipe, there are losses due to the resistance of water meters, valves, elbows, and other fittings. There is an additional pressure loss at an abrupt entrance to a pipe line and also at changes in pipe size — called the entrance head. Water meters, globe valves, and angle valves cause the principal losses. The resistance of these items varies considerably with different makes of equipment. TABLE 3 Approximate Maximum Number of Sprinkler Heads, with o Capacity of 2,5 Gallons per Minute at a Pressure of 1 5 Pounds per Square In