SPRINKER SYSTEMS - 3
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. Manu- facturers of supplies for lawn sprinkling systems sell these wrenches nd 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 sur- rounding soil, and the size of the system or line which must be drained into the excavation. On loamy soils and light clays an exca- vation 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.
|
