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[TD][SIZE=4][COLOR=green]Jess Stryker’s[/COLOR][/SIZE]
[SIZE=6]Landscape Irrigation Installation Tutorial[/SIZE]
[SIZE=7][COLOR=#990066]Installation of Underground Piping[/COLOR][/SIZE][/TD]
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</center>[COLOR=#990066]Preparation:[/COLOR]
[INDENT]A day or two before you begin digging the trenches, water the soil thoroughly to soften it, but try not to create mud. As you trench, periodically water down the area to keep down the dust. Recent research indicates that airborne dust is a serious health risk, it’s better to be safe than sorry! As previously mentioned, do-it-yourselfers should seriously consider hiring someone to do the trenching if you have more than 100’ or so to trench. You can often hire someone to do it for little more than the cost of renting a trencher. See the previous discussion of tools for more on trenching equipment and recommended tools. If you are digging the trenches by hand, I recommend doing it in sections. This has a couple of advantages, first you don’t completely wear yourself out digging, second it reduces the danger of having lots of open trenches at the same time. The bottoms of the trenches need to be as level and smooth as possible. If the trenches were dug by a machine don’t think you’re going to avoid a lot of shovel work! The trenching machines leave a lot of dirt in the bottom of the trenches that you will need to remove. You will need a narrow blade trenching shovel for this. If you have someone dig the trenches with a machine, have them over-excavate the trench by an extra 2". Then you can just leave the loose dirt in the bottom of the trench and save a lot of work!
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[COLOR=#990066]Trench Depth, Pipe Materials[/COLOR]
[INDENT]The depth of the trenches will vary dependent on a number of factors. [COLOR=#ff0000]All plastic mainline pipe must be at least 18" deep as measured from the top of the pipe to the soil surface. [/COLOR]So if you are installing a 1 1/2" mainline the trench is going to need to be about 20" deep. A mainline is any pipe which is under constant water pressure. In other words the pipe between the water source and the control valves is a mainline. Any mainline pipe that is not buried at least 18" deep should be metal, such as copper, brass, or steel. In most areas this is required by law (the Uniform Plumbing Code) but it just makes good sense to do it everywhere. You don’t want to hit this pipe with a shovel when planting a new shrub! As a side note if you use steel pipe, be sure to either use the plastic coated type or wrap the pipe with a special protective plastic tape (ask your supplier for the tape). Even the galvanized steel pipe will rust with time, I wrap it with plastic tape just to be safe. I don’t recommend using polyethylene for mainline pipes. Again, polyethylene is not legal for use as mainlines in most areas.
[COLOR=#ff0000]Lateral trenches for home irrigation systems can usually be about 10" deep. For commercial systems the standard is that the pipe is 12" deep, so the trench needs to be about 14" deep.[/COLOR] For the do-it-yourselfer the argument is more work now or more work later. The deeper the pipe, the less likely it is to be damaged.
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[COLOR=#990066]Freezing Climates[/COLOR]
[INDENT]See the full tutorial on [B]Winterizing your sprinkler system[/B].
In areas where freezing temperatures occur precautions must be taken to prevent water from freezing in the pipes, valves, emitters, and sprinkler heads. In most cases this is done by installing drain valves on the pipe and making sure the pipe slopes down to the drain valve so that the water can drain out. You need a separate drain valve on the section of pipe on both sides of every valve (the water can’t drain through the closed valve, right?). Automatic drain valves work well but there are a couple of important points to consider before you use them.
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[]Automatic drain valves open and drain all the water from the pipes every time the irrigation system is turned off. So you must provide someplace, such as pit filled with gravel, for this water to run into or you will create a mud hole!
[]Automatic drain valves waste water. If you pay a lot for water or live in one of the many areas where water is in short supply, you may want to use manual drain valves that you open by hand at the end of the irrigation season.
[]Because the automatic drain valves drain the pipes after each use, the pipes must refill each time you turn on the irrigation. This takes time and creates stress on the piping which can lead to premature failure.
[]If you just once forget to open the manual drain valves before the first freeze, you will wish you had installed the automatic drain valves instead. Can you faithfully remember to drain the system every year before the first frost? If not you better use automatic drain valves.
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For large irrigation installations such as parks and golf courses we don’t use drain valves. We install special taps on the pipes which are connected to a high capacity, low pressure, air compressor prior to the first hard freeze. The irrigation system is then run through its cycles using air in place of water. This blows out all the water from the system. As an added precaution I also install manual drain valves on all the mainlines just in case some water remains in the pipes. The drain valves are also handy for draining the system if you need to work on the pipes.
[COLOR=#ff0000]Trench depth is also an important consideration in freezing climates. Installing the pipe deeper gives it more protection against frost. Where possible, all the pipe should be installed below the soil frost line. Remember that you will still need drain valves in order to drain the water out of the sprinkler heads which aren’t below the frost line.
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[COLOR=#990066]Wiring[/COLOR]
[INDENT]Don’t forget to install the control wire for the valves while the trenches are open (unless, of course, you don’t plan to bury the wire). [COLOR=#ff0000]The wire should be at least two inches away from the pipe, and either next to, or under the pipe. Never place the wire above the pipe. My preferred location for the wire is 2-4" below the pipe. This way the pipe protects the wire from damage and you are less likely to accidentally cut the wires when making repairs to the pipe.[/COLOR] If you are using numerous wires rather than a multi-wire cable, it is easier to handle the wires if you tape them together into a bundle every 10’ or so. The size of each wire is determined from a chart provided by the valve manufacturer. Every valve model is different, but we can make some generalizations. For residential systems where the wire length between controller and valve (not the distance from controller to valve, but the length of the wire between the controller and the valve) is less than 200’, #18 wire size will work. #18 is the size of wire provided in most multi-wire (or multi-conductor) irrigation cable. Check the wire packaging or look at the small print on the wire itself to find the wire gauge (size). The standard wire gauge for commercial irrigation systems is #14 or sometimes #12. As the numbers get smaller the wire gets bigger, so #12 wire will carry more current than #14. The wire should be made for direct burial in the ground, if it is the wire will be labeled “UF-AWG” on the wire insulation. If you don’t mind a little extra expense, place the wire in a PVC pipe sleeve to protect it. If there are a lot of burrowing rodents (like gophers, moles, and ground squirrels), in the area I advise that you always sleeve the wires. They will chew on the wire and cause you no small amount of grief. While we’re talking about wiring this is a good time to warn you against a common temptation that has disastrous results. Never connect the wires to the irrigation controller and then “spark” the wires against each other to test them! This can damage the circuits in many of the irrigation control clocks. If you need to test the wire circuits the best cheap way to do it is to connect a valve to the wire with the controller turned off, then have someone turn on the controller station while you listen for the valve solenoid to click when the circuit is activated. The best professional way is to use an ohm meter to test the wire continuity.
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