Water Everything: Sprinkle System Basics

Sprinkling Systems
In most regions which have dry summers, sprinkling systems for lawns are commonplace. They are standard equipment on landscaped home sites, and they are found also on many sites that cannot be called planned in any sense of the term, but which are the property of people who like to see green grass in the yard. In such localities there is usually an adequate number of contractors who install lawn irrigation systems, and there is a considerable amount of common knowledge about such systems. Due partly to the energy of the contractors and partly to special local conditions, there is often one preferred type or make of system and residents see little virtue in any other. This is all to the good, for such strongly entrenched prejudices indicate that a system has been found which has given satisfaction in numerous installations over a period of years. This chapter, however, is aimed chiefly at the much larger territory where there are a few lawn sprinkling systems on the best properties, but where nature has not made them an absolute necessity.

Advantages of built-in sprinkling systems
Any sprinkling system, built-in or portable, has just one purpose: to supply moisture to the grass in times of drought, or when the rainfall is inadequate to keep the grass growing. In the so-called humid regions where prolonged dry spells are infrequent, built-in sprinkling systems appear to be a luxury. The economy-minded can always point out that they are used such a small fraction of the year that the capital investment in them is not justified. The fallacy of this argument can readily be shown up by dropping into any neighborhood hardware store during the summer and taking note of how well garden hose and portable sprinklers are selling. Garden hose and portable sprinklers are used for precisely the same purpose as built-in systems, but they are much less convenient and much less efficient. To the best of our knowledge, no one has totaled up all the costs and charges that would enter into determining whether lawn hose and portable sprinklers are more expensive in the long run than built-in systems, but it is our guess that they are. Hose costs money, and, under the care that it receives from the average homeowner, it does not have a long life. Portable sprinklers are likely to be flashy affairs which either wear out early or are soon replaced with some other device that looks in the hardware store, at least as if it would do a better job. The greater initial investment which must be made in a built-in system pays off immediately in greatly increased convenience. Such a system makes it possible for anyone who is strong enough to turn a small valve to water the lawn and to do the job well. Watering does not have to wait for the member of the family strong enough to wrestle with hose and sprinklers. Because the valves in a properly designed system are always located outside the sprinkling area which they control, it is not necessary to dress in old clothes in order to water the lawn. When the grass needs water, the water can be turned on and left on long enough to give it an adequate soaking. Then it can be turned off as simply, and there is no hose or other equipment that must be gathered up and put away. The chief result of all this convenience is that the grass almost always gets water at the right time and therefore remains green and alive. The cost of reseeding the lawn every two or three years to replace grass burned out during dry spells is therefore saved. Of all the devices which have been invented for supplying water to lawns and these range from the simple garden hose to elaborate machines which carry their hoses with them and walk almost hu- manly around shrubbery and other obstacles a built-in system is far and away the most efficient. It can accomplish the same amount of irrigation with less water, or accomplish more irrigation with the same amount of water, because it spreads the water more evenly.

A simple built-in sprinkling system for lawns which has all the features needed in most installations consists of a simple network of pipes which are buried under the lawn and to which are attached, at suitable intervals, short vertical pipes called risers, which extend from the horizontal pipe upward to the surface of the lawn. Sprinkling nozzles called "heads" in the trade are attached to the top of these risers. A suit- able number of hand valves are installed at convenient points in the system so that the water can be turned on and off in various parts of the lawn and regulated as desired. In regions where the ground freezes in winter some provision must be made for draining the pipes in the fall. Obviously there must also be a connection to some source of water supply, either a public system or a private one. That is all there is to a sprinkling system which is adequate for the average lawn. The grounds of large estates where there are really large expanses of grass, or intricate paths, or plantings, often require more elaborate systems in order to meet special conditions. Very large lawns, for example, are often watered with a combination of underground piping and portable sprinklers. The underground pipe is essentially a supply pipe and it is placed either along the border of the lawn or down its middle. At suitable intervals along the pipe connections are installed to which a hose or large sprinkler head can be attached. This kind of system requires someone to operate it; therefore, it is usually found on the properties of people who can afford to employ gardeners. It will be discussed in some- what more detail later in this chapter. In some installations the areas of grass or shrubbery which are adjacent to long stretches of path or driveway are watered from a line of pipe which is supported close to the surface of the ground and which is pierced at suitable intervals with nozzles that spray only in one direction. This scheme finds some use even on small sites. To simplify the discussion we will first take up the design and installation of a simple system.

The underground piping
Although both brass piping and copper tubing have been used for the underground pipe lines of built-in sprinkling systems, galvanized steel pipe, especially the alloy which is called copper-bearing, is probably the most suitable material for most sites. It costs substantially less than the other materials and, in a lawn sprinkling system, it usually has a long life.

Gate valve
Those who have had sad experiences with the corrosion and clogging of steel piping in plumbing systems in their houses are sometimes doubtful of the advisability of installing galvanized steel piping underground. However, the conditions are hardly comparable. An irrigation system is in use only a small fraction of the year. Furthermore the water in a sprinkling system is always cool. This makes a great difference in the rate of corrosion and clogging. In house plumbing systems it is almost always the hot water line rather than the cold water line that clogs up. Under certain very special conditions underground pipes are corroded by an electrical process called electrolysis whereby metal is actually carried away from the pipe by vagrant electricity. Trolley lines for streetcars used to be the main source of this trouble in cities.

The control valves
Two general types of valves are used on the pipe lines of built-in sprinkling systems. The gate valve has the advantage of providing a full waterway when it is fully opened and, therefore, it is always used on the main supply line and should be used on long branches. It is slightly more expensive than the globe valve; consequently, the globe valve is commonly used on short branches. Since a well-made gate valve will function longer without repair because it has no washer than a globe valve, it is doubtful whether any money is saved in the long run by using globe valves at any underground location in the system. If the sprinkling system can be planned so that the valves are located in the basement or some other place other than under the soil, globe valves can be used on all the short lines. The type of valve known as a stop is used for drain valves. If used for underground drain valves, these valves need only a quarter turn to open or close them. In comparison to the globe or gate valve, they operate rather stiffly; but this is not a disadvantage in the average sprinkling system because they are ordinarily operated only when the system is drained usu- ally once a year just before the beginning of freezing weather. All of these valves, supply and drain, are manufactured regularly in brass, a metal which will give good service underground. The valves which are to be placed underground should all be equipped with handles which can be grasped by standard wrenches. Manufacturers of supplies for lawn sprinkling systems sell these wrenches and also sell valves with the right style of handle. However, any good make of valve can be used if the wrench will fit; therefore, if you do not wish to buy your valves from the same firm as the sprinkling heads, buy the wrench and then shop for valves that will take the wrench. It is a good idea to lay in two or three wrenches because these are articles which are easily mislaid. Of course, if the system can be laid out so that it is not necessary to put valves underground, these special wrenches will not be necessary. The valve boxes. These are made of standard steel pipe cut to the desired length, which is of course the length needed to reach from the pipe line to the surface of the soil. Standard 3-in. pipe is the minimum size which is large enough for these boxes. It will pass the standard wrenches, and also it makes a fairly neat fit with the valve body at the end of the box. Either galvanized pipe or black pipe which is pipe without the zinc coating may be used for the boxes. The bottom end is simply rested on the pipe adjacent to the valve; that is to say, it is not necessary to cut it out in order to make it fit over the pipe, nor is it necessary to prepare the bottom end in any special way. If, at certain times of the year, the water table under the lawn is rather high, some soil may enter the box through the open bottom end. Cleaning this out with a long spoon or some other implement that serves the same purpose is a lot simpler than trying to make a fitting that will exclude the soil. On the average well-drained lawn the soil will not enter the box at all.

The valve box
is finished off at the top with a hinged cover. These covers are available from manufacturers of supplies for irrigation systems. They fit the top end of the box and they have a hinged lid which can be swung back when it is designed to operate the valve. 337. The drain pits. The soil around the supply control valve needs no special preparation, but on most sites it is necessary to make excavations under the drain valves and to fill these excavations with small stones or coarse gravel. The reason for doing it.

Drain pit
This is that water penetrates a tight soil rather slowly, hence draining the system would take a long time if it was necessary to wait for the water to drain away. However, if this tight soil is re- placed with a coarse material, the water drains away quickly, and the drain valves can be closed before one's patience becomes worn out. The necessary size of the excavation to be filled with coarse material depends upon two things: the nature of the surrounding soil, and the size of the system or line which must be drained into the excavation. On loamy soils and light clays an excavation from 1 to 11/2 ft. in diameter and about the same in depth is usually adequate. The adequacy of the drain pits is easily tested and should be tested before the pipe lines are covered. Simply operate the system for a few minutes, then shut off the water supply, and drain the lines through the drain valves. If the water disappears into the excavations rapidly, the pits can be assumed to be deep enough.

Sprinkling heads
A good deal of experimentation and experience have gone into the design of sprinkling heads for lawn irrigation; and the types and makes which are now on the market will usually give satisfactory service over a long time without repair and without maintenance other than occasional cleaning and minor adjustments. Some of the heads now available are designed to remain flush with the turf at all times. Others are so built that the part of the head which distributes the water automatically rises a few inches above the turf when the water is turned on, and drops back again to the level of the turf when the water is turned off. This latter type is known as a pop-up head. Pop-up heads are somewhat more ex- pensive than stationary heads because they have more mechanism, but most of them are designed to cover a somewhat larger area. Therefore, although pop-ups cost more, there may be some saving gained in the number of heads required and also in the amount of pipe required for the supply lines. It is now known that it is better for most grasses not to cut them too short. Pop-up heads are the more suitable type for long grass because they stand above it while sprinkling; whereas a heavy, long turf around the stationary type of head which is installed flush with the surface of the soil will interfere somewhat with the distribution of the water. On the other hand, pop-up heads are a little more likely to get out of order; and they will not operate satisfactorily on low water pressures. Most heads used in irrigation systems in lawns have a circular spray pattern; that is to say, a full head will distribute the water over a circular area. However, there are heads on the market which cover an area of lawn which is approximately square. The advantage claimed for the latter type is that it does not waste water since there is no overlapping of areas sprayed by adjacent heads. The spray pattern of a system using circular heads is shown in As the diagram shows there is a certain amount of overlapping which can- not be avoided, since the alternative would be gaps between the spray patterns where the grass would not get watered at all, or watered very lightly. The spray pattern of a system using square heads VARIES. It is claimed that the amount of water saving with the square heads is about 35 per cent. Undoubtedly the water saving is considerable and also important where the water is metered. However, lawn sprinkling systems are not operated in closed rooms. They are operated out of doors where there is, in most regions, enough breeze most of the time to interfere considerably with the spray pattern produced by any type of sprinkling head. It is doubtful therefore, whether anyone can select a special type of head and be certain that his saving of water will be a certain specific percentage. A good policy in selecting heads is to use a type and make which your neighbors have found satisfactory. If you want to experiment with other and perhaps novel types, buy only one or two of them at first and try them out. Such a procedure does not give the inventor or manufacturer who is promoting the device the best of opportunities, but it does place upon him the burden of proving that his particular variety of head is superior. Except where water is unusually high priced, durability and freedom from clogging are probably more important qualities than a theoretical saving of water. This statement should not be construed as a warning against using the type of head which produces the square spray pattern. It is merely intended to point out that one should look for several qualities, only one of which is economy in the use of water.

Spray pattern of square heads
Although most heads used in installations are the full-area type, that is to say, they spray a full circle or a full square, it is necessary to use modified heads in most systems. For example, if full-area heads were used along the curving walk in the walk, as well as the adjacent lawn, would be sprinkled whenever the heads were in operation. However, by using, at appropriate points, heads which are built so that they spray only one-quarter or one-half the normal area, the grass receives its full quota of water right up to the edge of the walk and the walk is not wet. These modified heads are available in styles that will produce one-half, one-quarter, and three-quarter patterns. The shape of many lawns makes it impossible to lay out an irrigation system so that standard full-area heads can be used at every point. We have just explained how boundaries are taken care of, but there is still one other variation necessary. Say that the normal coverage of the heads obtainable is a 12-ft. circle or a 12-ft. square, but the lawn includes a strip of grass which is only 8 ft. wide. This problem must be handled by using an adjustable head. Adjustable heads are offered by practically all manufacturers. In most makes the adjustment is very simple and consists of something like a brass screw which can be turned in with an ordinary screwdriver. As it is screwed in, the screw restricts the size of the waterway within the head and thereby reduces the size of the spray area. Unless the water used is exceptionally clean, adjustable heads, especially after the waterway has been reduced by turning down the screw, are subject to clogging. They do not clog often unless the conditions are very bad, but any clogging is somewhat of a nuisance. Because of this difficulty, they should be used only where necessary. A different type of nozzle or head which is often needed in small systems as well as large is the shrubbery head. It is installed on a riser pipe which extends above the ground about to the top of the shrubbery. Usually the length is adjusted so that the shrubbery just conceals the sprinkling head, but does not obstruct the flow of water. Shrubbery heads are necessary where there are large clumps of plantings which must be watered, or where the placing of a clump makes it impossible to water an adjacent strip of grass with a standard head. If it is properly installed, the shrubbery head can give adequate irrigation to both shrubbery and adjacent lawn in difficult areas of many shapes and sizes.

SPRINKLER SYSTEMS - 5

Planning the system
There is nothing complicated about the design or the installation of a lawn irrigation system, but there are certain principles which must be understood and followed if the system is to operate satisfactorily. A poorly designed system fails to achieve its full purpose and also wastes water. If there are substantial areas not reached by the sprinkling heads when the system is in normal operation, there will be patches of grass damaged by drought even though the sprinkling system is used. Almost as bad is too much overlapping, as this defect produces sizable soggy areas in the lawn. Where water is metered and the rates are high, or where there are some limitations on its use; it is essential that the system be laid out so that it is efficient. There are two ways of obtaining a lawn sprinkling system. The first is to select a contractor who has a reputation for making good installations and to give the work to him. He will look over your grounds and probably discuss with you what special features you want such as special locations for the valves; but after you have stated your views on these points, you will not be concerned with the design or installation problems at all. You will only have to pay the bill when it comes in. The other method is to buy the supplies and install the system yourself. The discussion from this point on will assume you are going to follow the latter procedure. The first step in designing and installing a system of your own is to select a source of supply, especially to decide which manufacturer's heads you are going to use. Once you have made this decision, obtain from this manufacturer whatever information he has available for homeowners about the installation of his system. This information should include not only a description of the heads, but also data on the water pressures required and the areas covered by the heads when they operate at different pressures. Most manufacturers also furnish some information on how to figure the all- important subject of pressure drop due to friction in the supply pipe and branches.

Drawing the Plan
The type of ruled paper known as graph paper provides a convenient way of drawing the necessary plan without pain or too much effort. First measure the lawn and outline it on the graph paper according to the scale you have adopted. Next mark on the plan the locations of the sprinkling heads, giving them the spacing recommended by the manufacturer for the water pressure you know will be available. Typical spacing’s for stationary heads are 10, 12, 14, or 16 ft., but don't guess at the spacing and especially important don't overestimate it. It is well to use symbols to indicate the different styles of heads so that you will not make a mistake in ordering them. Selection of the water pressure to be used as the basis for the spacing is a critical point. City water pressures are often stated in terms of the maximum rather than the minimum, whereas lawn irrigation systems are often used at times when the pressures are considerably below maximum. It is good procedure to obtain from the offices of the utility which supplies the water a statement of the minimum pressure that can be expected under summer conditions in your locality. The value given should then be used as the design pressure for the system. If sprinkling is done at times when the water pressure is considerably in excess of the minimum pressure, the situation can be controlled by only partly opening the supply or branch valves. In spotting the heads, locate them so that overlapping of the spray will theoretically not occur with square heads and will be held to a minimum with circular heads. However, in the case of circular heads, do not make the mistake of spotting them so that there are even small unwatered areas between the areas covered by adjoining heads. Observe the correct relationship between adjoining circular heads. If the area where the system is to be installed is very irregular, it sometimes helps to cut templates which represent, in the scale you are using, the areas covered by full, half, and quarter heads. The templates can then be shoved around on the plan until the best possible arrangement of the heads is arrived at. Once the location of the heads is determined, the next step in design is to locate the valves. On small lawns, the only valve needed is one in the supply line; but on lawns of moderate and large size, it is usually advisable to plan the system so that it can be operated in sections. If the system is so large that all of it cannot be operated at one time from the available water supply, such an arrangement is, of course, essential. It is a convenience when you wish to water part of the lawn while you use another part for recreation. Very often it is discovered after a lawn sprinkling system is in- stalled that the water supply pipe which runs from the water main in the street to the house is too small to handle both the sprinkling system and the house plumbing system simultaneously. Such a condition can be expected if, before the sprinkling system is installed, the opening of several faucets on the lower floor of the house causes a considerable diminution of the flow from faucets on the floor above. Robbing of the house plumbing by the sprinkling system sometimes develops even when this test does not foreshadow it. The condition can be remedied by installing a new supply pipe.

Planning the system
There is nothing complicated about the design or the installation of a lawn irrigation system, but there are certain principles which must be understood and followed if the system is to operate satisfactorily. A poorly designed system fails to achieve its full purpose and also wastes water. If there are substantial areas not reached by the sprinkling heads when the system is in normal operation, there will be patches of grass damaged by drought even though the sprinkling system is used. Almost as bad is too much overlapping, as this defect produces sizable soggy areas in the lawn. Where water is metered and the rates are high, or where there are some limitations on its use; it is essential that the system be laid out so that it is efficient. There are two ways of obtaining a lawn sprinkling system. The first is to select a contractor who has a reputation for making good installations and to give the work to him. He will look over your grounds and probably discuss with you what special features you want such as special locations for the valves; but after you have stated your views on these points, you will not be concerned with the design or installation problems at all. You will only have to pay the bill when it comes in. The other method is to buy the supplies and install the system yourself. The discussion from this point on will assume you are going to follow the latter procedure. The first step in designing and installing a system of your own is to select a source of supply, especially to decide which manufacturer's heads you are going to use. Once you have made this decision, obtain from this manufacturer whatever information he has available for homeowners about the installation of his system. This information should include not only a description of the heads, but also data on the water pressures required and the areas covered by the heads when they operate at different pressures. Most manufacturers also furnish some information on how to figure the all- important subject of pressure drop due to friction in the supply pipe and branches.

Drawing the Plan
The type of ruled paper known as graph paper provides a convenient way of drawing the necessary plan without pain or too much effort. First measure the lawn and outline it on the graph paper according to the scale you have adopted. Next mark on the plan the locations of the sprinkling heads, giving them the spacing recommended by the manufacturer for the water pressure you know will be available. Typical spacing’s for stationary heads are 10, 12, 14, or 16 ft., but don't guess at the spacing and especially important don't overestimate it. It is well to use symbols to indicate the different styles of heads so that you will not make a mistake in ordering them. Selection of the water pressure to be used as the basis for the spacing is a critical point. City water pressures are often stated in terms of the maximum rather than the minimum, whereas lawn irrigation systems are often used at times when the pressures are considerably below maximum. It is good procedure to obtain from the offices of the utility which supplies the water a statement of the minimum pressure that can be expected under summer conditions in your locality. The value given should then be used as the design pressure for the system. If sprinkling is done at times when the water pressure is considerably in excess of the minimum pressure, the situation can be controlled by only partly opening the supply or branch valves. In spotting the heads, locate them so that overlapping of the spray will theoretically not occur with square heads and will be held to a minimum with circular heads. However, in the case of circular heads, do not make the mistake of spotting them so that there are even small unwatered areas between the areas covered by adjoining heads. Observe the correct relationship between adjoining circular heads. If the area where the system is to be installed is very irregular, it sometimes helps to cut templates which represent, in the scale you are using, the areas covered by full, half, and quarter heads. The templates can then be shoved around on the plan until the best possible arrangement of the heads is arrived at. Once the location of the heads is determined, the next step in design is to locate the valves. On small lawns, the only valve needed is one in the supply line; but on lawns of moderate and large size, it is usually advisable to plan the system so that it can be operated in sections. If the system is so large that all of it cannot be operated at one time from the available water supply, such an arrangement is, of course, essential. It is a convenience when you wish to water part of the lawn while you use another part for recreation. Very often it is discovered after a lawn sprinkling system is in- stalled that the water supply pipe which runs from the water main in the street to the house is too small to handle both the sprinkling system and the house plumbing system simultaneously. Such a con- dition can be expected if, before the sprinkling system is installed, the opening of several faucets on the lower floor of the house causes a considerable diminution of the flow from faucets on the floor above. Robbing of the house plumbing by the sprinkling system sometimes develops even when this test does not foreshadow it. The condition can be remedied by installing a new supply pipe.

Layout of a Sprinkling System
Layout of a sprinkling system designed so as to place the valves in the house basement. adequate size, but the cost of this operation can be circumvented by putting enough valves in the sprinkling system so that the number of heads going at one time will not be great enough to rob the plumbing. It is very convenient to have all of the valves in a lawn irrigation system located at one spot. However, if there are several branch lines which should be separately controlled, putting the valves in one place, for example inside the basement or at the edge of the terrace, requires some extra pipe. If you elect to save pipe and therefore do not locate the valves together, it is advisable to install the valves which control the branch lines so that they can be operated outside of the area «wet by the heads on any particular branch when it is in operation. This arrangement also uses some extra pipe, but the slight additional cost is amply repaid by the convenience of being able to turn the valves on or off without getting wet. Most manufacturers of supplies for lawn irrigation systems have a customer service, the function of which is to advise homeowners on the design of systems. These services will design a system to suit a particular lawn on the basis of a rough sketch of the lawn and other information furnished by you; and they will also check your own plan if you care to submit it. The design of a lawn sprinkling system is essentially a simple matter; nevertheless it is a good idea, once you have drawn your plan, to send it off to the manufacturer whose heads you intend to use and ask for criticism and advice.

Private water supplies
Whether a private water supply system can be used as a source for a lawn sprinkling system depends upon two factors: the type of system and the amount of water available. Systems in which the water flows by gravity to the house in adequate quantity for all the needs of the household and for lawn sprinkling besides can be used if the water is under sufficient pres- sure to operate standard sprinkling heads. Inasmuch as heads are available which will operate under 15 pounds pressure, or even less, pressure is not often a problem if the amount of water is sufficient. If the water must be pumped, there still must be an adequate quantity available; but the limiting factor is often the pump. The usual types of domestic water supply systems which are powered by a small electric motor are designed for intermittent operation and may wear out rapidly if they are run steadily for several hours. On the other hand, some of the larger domestic water systems are not damaged at all by steady running so long as they are given pro- per maintenance. There is no general statement which can be made that will be of much help to you in determining whether a particular water system will stand up under the work that a lawn sprinkling system would put upon it. However information as to whether the system can be operated continuously without damage can usually be obtained from its manufacturer. The capacities in terms of gallons per hour of domestic water systems is freely stated in catalogs and also is sometimes printed on the pump or tank of the system itself. It is an easy matter to compare this capacity with the minimum requirements of the sprinkling system. A round figure for rough estimates is that each head in operation will require 2Yi gallons of water per minute, but in the actual design of systems the more exact figures, supplied by the manufacturer of the heads, should be used.

INSTALLATION PROCEDURES
The first step in actual installation is to mark the positions of the pipe lines and valve boxes with stakes. Any sort of stout stake that will hold a stretched cord is suitable. The stakes should be firmly driven so that they will not be knocked out of place while the digging is going on. Even long pipe runs need only two stakes, one at either end, if the run is straight. After the stakes are driven, a cord may be stretched between each pair and left in place; or it may be stretched and the route of the pipe marked with a streak of garden lime, after which it can be taken down. Stakes which mark the positions of the valve boxes should be set to one side of the line so that they can remain in place while the digging proceeds.

Cutting the turf
One of the good points about underground lawn-irrigation systems is that they can be installed in established lawns without disfiguring the lawn at all. It is necessary only to use reasonable care in cutting and handling the turf, and in re- placing the soil and the turf after the installation is completed. The turf should be cut so that the center line of the pieces will come approximately over the line of pipe. Cut in this way the turf, when it is replaced, will form a sort of tough blanket or membrane over the area of soil which was disturbed the most and will tend to conceal it. If the installation is going to be carried out within a day or two, the cut turfs can be stacked alongside the cut. However, if the installation will take longer than two days, it is best to pile them elsewhere to avoid damage to the adjacent grass. If the turfs do not have to be removed from the lawn, they can be cut rather thick and each turf placed beside the area from which it was removed. If this procedure is followed, the turfs can be handled so that when replaced they will re-establish themselves and continue growing practically without interruption. Another advantage is that the turfs need not be cut to a uniform size since each will go back into the hole from which it was removed. However, if the turfs cannot be handled this wav, they should be cut uniformly so that each can be put back anywhere along the line without special fitting. Pieces of turf are removed by cutting all around the border with a sharp, narrow spade, then inserting the spade underneath the turf and cutting it loose. Turfs which are not to be moved far can be cut 4 or 5 in. thick; 2 to 3 in. is a better thickness for those which must be moved a distance. Once it is cut loose, a fairly large turf, up to about 15 in. square, can easily be lifted with an ordinary spade.

On new lawns there is, of course, no turf in the way. The underground irrigation system should be installed before the lawn is seeded. You will find that the irrigation system will be a great help in obtaining good germination of grass seed, and that it will function as insurance against the killing of the young grass by dry weather before it has established a good root system. Digging the trenches for the fife. Even in regions where the winters are extremely cold it is not necessary to bury the pipes of lawn-sprinkling systems deeply, because they are always emptied of water before the ground freezes. However, the lines cannot be installed just under the surface of the ground because streaks may consequently develop in the grass immediately over the pipes, owing to inadequacies of moisture and plant food in the very shallow soil. Depths of 8 to 12 in. are preferred for the pipe lines because these , are not deep enough to require excessive labor and yet are deep enough to avoid any visible effect on the grass above the pipe. The general principles of ditching are discussed in Sec. 376. In making trenches for the lawn sprinkling system, the width of the trench is determined not by the width of the pipe to be installed, but by the width of the spade; therefore, buy or somehow obtain a narrow spade, even though you are not going to have to dig more than one hundred feet of trench. Insert the spade to approximately the same depth every time you push it into the ground so as to make the bottom of the trench as even as possible. It is much better to lay the pipe lines on undisturbed soil than on soil which must be put back to fill hollows which were dug out unnecessarily. Pile the soil evenly to one side of the trench in such a way that it can easily be raked into the trench after the system is completed. Large stones and ledges of bedrock will create difficult problems in the installation of any underground piping. If the soil of your lawn contains such impediments, it is advisable to dig the trenches to the minimum depth which has been suggested rather than to the maximum. If ledges and large stones are encountered even at a depth of 8 in., there is no short cut around them. It will be necessary to dig the stones out and fill the holes by tamping soil. Ledges will have to be cut through. Pipe can be safely bent over stones and ledges only in regions where the ground does not freeze in the winter. In other regions the "humps" produced by bending the pipe would interfere with draining it in the fall. As we have already mentioned, in fine-grained soils, especially the firmer clays, it is necessary to construct small pits underneath each drainage valve to facilitate seasonal draining of the system. The positions of these pits will be indicated by the stakes you have set to locate the valve boxes. When you come to these points, merely enlarge and deepen the trench sufficiently so that there will be adequate pits underneath the drain valves. Before the pipe is laid, these pits should be filled with coarse gravel or with small stones averaging about one inch in diameter, either of which materials should be firmly tamped in place and brought up to the level of the trench bottom. Grading of the underground pipe lines so that they can be completely drained is absolutely essential in all climates with freezing winters. Not much of a slope is required; in fact 1 in. in 20 ft. is quite adequate if the trench bottoms are made without humps or sags, so that the pipe lines rest evenly. Trenches which carry sewer lines or lines of drain tile can be sloped only in one direction; but there is no such restriction on the lines of a lawn-sprinkling system since drain valves may be placed wherever they are needed. It is desirable, however, to use only as many drain valves as are absolutely required. Not only does each one add to the cost of the system, but, if they are numerous, some may be overloaded when the system is drained. In a small system, rectangular in shape, all the lines are usually sloped so that they can be drained back to a single point, usually adjacent to, or integral with, the supply valve. This is the simplest and the most convenient arrangement for drainage. However, the shape and grading of many lawns make this ideal solution impractical. In such lawns the slopes of the pipe lines in the system must be planned and carried out so that opening of all the drain valves, wherever they are located, will empty all of them. line of pipe in which the high point is somewhere between the two ends must be drained toward both ends; whereas a line in which there is a point between the two ends which is lower then either end can be completely drained only through the lowest point. These are the principles which must be kept in mind in planning the location of the drain valves whether the grading of the system is simple or complex.

Drain location under special conditions
Cutting and threading the fife. No special technique is required in the cutting and threading of pipe for underground systems other than ordinary care. The pipe threader should be adjusted so that it produces a length of thread on the pipe ends which is just long enough to screw into the fittings, leaving almost no thread exposed. This detail is important in underground systems because the pipe threader removes the protective coating of zinc from the outside of the pipe and leaves the bare steel exposed. The chief difficulty that occurs in the operation of lawn sprinkling systems is due to inadequate pressure at the heads which are most distant from the supply pipe. It can be largely avoided by taking pains to ream out the ends of the pipe after they have been cut and threaded so that there will be no internal spurs to restrict the flow of water. Another precaution which also is aimed at maintaining the full waterway within the pipe is to put thread compound only on the male end of the pipe. If compound is placed on the female end, some of it will inevitably be pushed into the interior of the pipe or fittings, where one of two things will happen to it. Either it will gradually be loosened and carried along in the water to clog the sprinkler heads, or it will harden and form obstacles to the flow of the water. An excess of compound placed on the male threads does not enter the pipe or fittings but backs up along the threads where it adds a little extra protection against corrosion of the joint.

Assembling the pipe
Square-nosed wrenches for holding the brass valve bodies and Stillson wrenches (pipe wrenches) are the tools needed for assembling the cut and threaded pipe and the fittings. The jaws of the Stillson wrench inevitably will cut through the galvanized coating on the exterior of the pipe. It is a good idea to paint these cuts after the joints have been assembled with a paint which contains a lead oxide base. If the joint compound you are using is red in color, it is probably made from a lead compound and should serve very well to paint these scratches. It is more convenient if rather large sections of the underground piping can be assembled above ground and lowered into the trenches after they have been put together. Given the right conditions, rather large blocks of such piping can be put into the trenches in one piece. The requirements are fairly straight trenches and enough men on hand to lower the network of assembled pipes without putting too much strain on the joints. The system can be built inward from the risers to the supply line, or it can be built in reverse, from the supply line outward to the risers. The first-mentioned procedure requires the use of a union where the system is joined to the supply line. If this union will be underground, it is advisable to use the type of union which has a ground joint. The type which uses a washer is not very good underground. Leaks may develop because of the washer drying out during the long periods when the system contains no water. 348. Once the system has been assembled, the joints should be tested. The test can be carried out by this method: The water is turned on and allowed to flow out of the tops of the risers. This carries the air out of the pipes and also removes any loose dirt which is not too heavy to be carried up the risers. After the water has flowed a few minutes, it is turned off and each riser is capped with a standard pipe cap. The water is turned on again and the joints are observed over a period of at least an hour. If a leak can be dis- covered in such a test, it is absolutely necessary to take the joint apart and correct the fault. Very often the leak turns out to be due to the joint not having been screwed together tightly. This is easily remedied. If the leak is due to a defect in the thread either on the pipe or on the fitting, it is necessary to correct it. Unfortunately, there is a tradition that small leaks in new piping systems will correct themselves when rust forms in the joints. Such self-healing does occur occasionally on steam lines in domestic heating systems; but it seldom, if ever, occurs on lines carrying cold water. Instead the tendency is for the leak to grow worse as more water passes through it. The last operation before filling in the trenches is setting of the boxes around the valves. We have already mentioned that these boxes are made of ordinary steel pipe. No threads are required on the pipe. The boxes should be placed over the valves and supported with stones or tamped soil sufficiently so they will not be knocked out of place as the trench is filled. The tops of the boxes should be made fairly level.

Burying the pipe
All of the soil that was removed from the trench should go back into it without difficulty. It should be returned to the trench in moderately thin layers, and each layer should be tamped somewhat before the next layer is placed upon it. If it appears, when the trench is about half filled, that all of the soil is not going to go back into it, wet the soil in the trench thoroughly. Water helps materially to settle the soil and to carry it into pockets that may be left vacant even after vigorous tamping. When the trenches are filled and covered again with turf, they should be even with the adjacent soil. If there is any variation in the level of a newly filled trench, it should be a slight mound rather than a depression. A depression will grow worse as time passes, whereas a slight mound may eventually settle to the level of the lawn. Sometimes it happens that the soil of the lawn contains loose stones, and it seems to be a quirk of human nature that these stones will be sorted out and carried off. Carrying them off is justifiable if it is done in anticipation of the necessity of digging up the pipe lines at some future date. However, it is well to bear in mind that the stones do occupy space which, if the lawn is to be level after the installation of the irrigation system, should be filled in with an equivalent amount of soil. This means bringing soil to the trenches from some other place. 350. Re- laying the turf. Before the cut turfs are replaced, it is good practice to moisten the soil on which they are to be placed. In fact, if you are nervous about the re-rooting of the turfs, it is not a bad idea to make up what the gardeners call a starter solution. This can be done conveniently by dissolving a handful of fertilizer in a large sprinkling-can of water. If this solution is sprinkled over the soil, it will speed up somewhat the process of re-establishment. However, do not use too much fertilizer or there will be dark green streaks in your lawn for some time. The turfs tend to increase their bulk somewhat during the short period when they were detached from mother earth; and consequently when they are replaced, they may stand slightly above the surrounding turf. A good way to correct this is to soak the lawn thoroughly, using the newly installed system, and then to roll the strips with a light lawn roller. If the soaking has been thorough, relatively light pressure will restore the original level.

OTHER TYPES OF SPRINKLING SYSTEMS
All of you who play golf, and some of you who don't, are familiar with the fact that many golf fairways are watered with large rotating sprinklers. This type of sprinkler is used on large areas, not because it does any better job of wetting the turf than the type which has been described, but because it is cheaper to install. Note that only a single underground line of supply pipe is required to cover a large breadth of grass. This relatively broad coverage is possible because one of the large sprinklers has a "throw" that is several times greater than the "throw" of a regulation lawn sprinkling head. A variation of this system which requires even less pipe for an equal area of grass. Here, instead of attaching the rotating arm directly to the riser, a length of hose is attached to the riser and the sprinkler is attached to a fixture at the opposite end of the hose. By moving the sprinkler fixture from time to time, a much larger area can be covered from one riser.

Using large rotating sprinklers
Systems of this type are as adaptable to the needs of large estates with expansive lawns as they are to golf courses. However, they are neither so adaptable nor so convenient as the kind of system in which stationary heads are used. The borders of the area watered are somewhat uneven because it is not possible to do as precise a job of sprinkling the borders of areas as can be done with stationary heads. Another bad feature from the homeowner's point of view is that the attaching of the sprinkling head is a manual operation. The sprinkler must be attached and allowed to operate for one or more hours; then, in order to cover another area of grass, it must be moved. Such tasks are all in the day's work for professional gardeners, but they don't fit well into the routine of the average homeowner. Still another variation of this idea does away entirely with underground piping. Instead of the buried supply pipe, a portable supply line is used. Portable lines are made of lightweight tubing and are equipped at the ends with special fittings which permit the length of tubing to be virtually snapped together without special tools. Short risers are attached to some sections of tubing, and the sprinkling heads are attached to the risers. Both the sprinkling head and the tubing must be moved about in order to operate the system.

Irrigation with overhead lines of pipe
Irrigation from overhead pipe lines is an old technique in vegetable gardens, especially in areas where such gardening is carried on intensively. We shall make no attempt here to discuss large systems of this type, but small systems consisting of one or two lines of pipe are of interest to some homeowners because of their potential use in the home garden. In irrigating large truck gardens, the pipe lines are usually installed permanently and are placed high enough so that horses and tractors can be driven under them without interference. In the home garden it is often more convenient to use two pipe lines, one on each side of the garden, than it is to have an elevated line of pipe within the garden's interior. It is more conventional though to place the pipe line down the center of the garden and to support it at a height of about 3 ft. The advantage of the higher location has already been mentioned. However, it is easier to reach the line when nozzles become clogged or something else goes out of order, if it is supported at a lower height. Everything considered, the low-post installation is better for the home garden than the high-post. Although both the posts and pipe line can be removed rather easily, it is better to plan the installation so that they can remain in place the year round because, even under the best of circumstances, taking the pipe down or putting it up is the kind of nuisance task that nobody likes to do. The essential elements of such a system are the overhead pipe line, the nozzles, the union which permits turning of the entire pipe line, the supply riser, and the supports In making large installations, the pipe is usually purchased without the nozzles and is drilled and tapped to receive them just before installation. This is an inconvenient method for the small homeowner because special tools are necessary for drilling the holes and cutting the thread. Fortunately the manufacturers of supplies for this kind of irrigation system offer lengths of pipe with the nozzles already installed. The same manufacturers also supply the turning union, the pipe brackets, etc. A handy device which is not shown is a special hydraulic machine which is attached to the supply end of the pipe and is operated by water pressure in such a way that it slowly rotates the length of the pipe. In fact these motors can be arranged so that they rotate the pipe slowly in one direction, then reverse themselves and, slowly turning it back, continue the process until they are shut off. Also they can be arranged so that they will shut themselves off after a predetermined period of time. If you decide to use one of these motors, you will probably elect to place one line of pipe down the center of your garden rather than two lines at the sides, because one is required for each line of pipe; and they are not inexpensive.