Prepared by W. Bryan Smith, Area Extension Agent, Agricultural Engineer, Clemson University. (New 5/08.)
There are many types of piping available – CPVC, PVC, galvanized iron, and polyethylene just to name a few. The two piping types most commonly used for irrigation systems are white PVC (polyvinyl chloride) and “black roll pipe ” (polyethylene).
PVC is generally the piping of choice in the Southern region. It is easy to work with, inexpensive, and quite common. PVC comes in a number of varieties, but the two used for landscape irrigation are Schedule 40 and 160 psi “ pressure-rated” (or PR160) piping. Both of these PVC types will work well for landscape irrigation systems. Schedule 40 piping has a slightly thicker wall than PR160 in sizes below 6 inches in diameter and can withstand higher pressures, but the thicker wall also means that Schedule 40 is slightly more expensive and that there will be more pressure lost to friction. Schedule 40 is somewhat more forgiving if installed in rocky ground. Either type will work well.
PVC comes in 10 or 20 foot lengths (depending on the supplier) and is glued together with PVC cement. Most PVC piping has one “belled end” or coupling made into the end of the pipe. Schedule 40 fittings are used on both PR160 and Schedule 40 PVC pipe. Be careful not to buy drain, waste and vent (DWV) PVC fittings – they are less expensive, but they are not designed to handle higher pressures and may fail over time.
Figure 1. PVC pipe.
(Photo credit: Bryan Smith)
“Black roll pipe” is commonly used for landscape irrigation systems in Northern areas and is used occasionally in the South. The pipe comes in 300 foot rolls and is connected with insert fittings and clamps. Black roll pipe is somewhat more difficult to install, but not appreciably so.
Black roll pipe is used in Northern areas because it will expand a small amount, which allows the water in it to be frozen with little or no damage – an important characteristic in the North. In the South we typically will not have pipe freezing problems if we install the piping to the recommended 12 inch depth. Either black roll piping or PVC piping will work well in our climate, but you may find the PVC piping easier to install and repair.
Figure 2. Black Roll pipe.
(Courtesy Newberry Hardware)
Just imagine that your sprinkler system is installed and working nicely. Uncle Bob stops in to visit, and as he leaves he backs into the yard – right over a sprinkler. The sprinkler is crushed, of course, but since the sprinkler was screwed directly into the PVC pipe, a good portion of the pipe below ground is broken, too.
We can’t prevent a sprinkler from being broken in this fashion, but we can protect the piping. Most manufacturers offer a product called “swing pipe” or “funny pipe.” This piping looks a great deal like drip tubing, but it has a much thicker wall and can handle higher pressures.
Swing pipe is installed between the PVC piping and the sprinkler to allow some flexibility if the sprinkler is crushed or driven over. Usually two feet of swing pipe will be used to attach a sprinkler to the PVC, but three or four feet may be used if needed. Swing pipe allows the installer to move the sprinkler around a little during installation just in case a planned sprinkler location turns out to be right behind a tree or an obstacle.
Figure 3. A spray head installed with swing pipe.
(Courtesy Hunter Industries)
Swing pipe is relatively inexpensive and will certainly pay for itself if even only one repair of this type is required. Special fittings are sold for the swing pipe to attach it to the sprinkler and the PVC piping.
Many types of piping are available for irrigation systems, but PVC Schedule 40, Pressure-rated PVC, and black roll pipe are suitable for this use. Drain, waste and vent (DWV) PVC is not suitable due to a low pressure rating. Other piping types are either too expensive or too difficult to work with in the landscape.
Adapted from the 2007 South Carolina Master Gardener Training Manual.
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