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There are any number of ways you can attach a sprinkler head to the lateral pipe. (Lateral pipe is the term used for the piping that runs from the control valve to the sprinkler.) The pipe and fittings used to attach the sprinkler to the lateral pipe is called a "riser". In addition to sprinkler heads, valves and backflow preventers also have risers that attach them to the pipe, so don't get confused by the multiple uses of the word "riser". Back in the early days of sprinkler systems, the sprinklers, valves and backflow preventers were all above ground, so the riser "rose up" from the underground pipe to the sprinkler or whatever above ground. Now, however, many sprinklers, valves, and backflow preventers are installed under ground. But the name riser is still used. OK, I've bored you enough with the arcane history of sprinkler system part names!
Simple Pipe Risers (i.e.; Nipples):
One of the most common sprinkler risers used for residential systems is a simple short section of pipe called a "nipple". Actually a nipple is the standard plumbing term used for any short section of pipe regardless of where it is used. (Those old-time plumbers were apparently a bunch of dirty old men!) While a nipple is the least expensive riser type, it also has some very distinct disadvantages. If the nipple is made of metal the nipple won't break. Even a rigid PVC plastic nipple is not likely to easily break (although I have seen it happen.) Now this may seem like a good thing, as we don't generally want things to break. However, when stressed something WILL break, and when your mower wheel hits the sprinkler there is going to be a lot of stress! If the nipple is metal or PVC it is probably not going to break-- which means either the sprinkler head or the lateral fitting under the nipple will break instead. The sprinkler head is expensive to replace if it breaks but fortunately it doesn't usually break. Unfortunately, what usually does break is the fitting on the lateral pipe. While not expensive, it is a real pain in the behind to replace it. So if you want to go the really cheap route and use a nipple for the riser I suggest that you use a "poly cut-off riser". A poly cut-off riser is a short pipe section (typically 6" long) with multiple sets of threads on it (see photo below.) You simply cut it off to the desired length with a knife or a pipe cutter. Because the poly material is very soft, the nipple will bend under stress and will break before either the sprinkler or the fitting break. When cutting the poly cut-off riser always cut it at the top of one of the sections of thread, as shown by the arrows in the photo below. Cut-off nipples generally cost less than a dollar a piece, which is pretty inexpensive to replace. Keep in mind that sooner or later you are going to have to replace a few of them. After all, they're designed to break! So buy a few extra when you install your system. You don't need to use thread sealants like Teflon tape on poly risers, the soft plastic will seal itself. Amateurs should never use liquid or paste thread sealers on sprinkler systems, if some of it squeezes through the threads to the inside of the pipe the water will take it straight to the sprinkler nozzle where it will clog the nozzle.
Poly Cut-off Riser
The arrows show where to cut the riser to shorten it.
A much better solution for risers is to use something designed to allow the sprinkler to move slightly. The riser most professionals use is referred to as a "swing joint" or "swing riser". In addition to deflecting to prevent breakage, most swing risers also allow the sprinkler head location to be easily adjusted. With the swing riser types known as "flexible arm swing risers" and "quadruple swing risers" the sprinkler head doesn't need to be directly over the lateral pipe fitting, so it is not nearly as critical that the pipe be installed in the right place. Thus the trenching and pipe installation is going to be much easier and faster. I don't know about you, but I like methods that are easier and faster-- especially when they also give better results! By the way, 4 to 6 inches is the normal distance a sprinkler should be from a sidewalk. (Before you ask, no, a 6 inch distance does not cause a dry spot along the edge of the sidewalk.)
Flexible Arm Swing Risers:
Don't use these flexible arm swing risers with rotors that have a 3/4" or larger inlet. That means don't use them with most rotors! See the rigid riser below for 3/4" and larger inlet size rotors.
The flexible arm swing riser is cheap and easy to install but not as durable as a rigid arm swing riser (but it is still much more durable than the cut-off riser mentioned above). This is the method I recommend for a residential or even a light commercial application, and it is what I use on the majority of my fast-food restaurant irrigation systems. It provides a good balance between cost, ease, and durability. The flexible arm swing riser consists of a length of flexible pipe (sometimes referred to as "Funny Pipe ®" a trademarked name of the Toro Company) with a insert ell on both ends. One ell attaches to the sprinkler, the other to the lateral pipe fitting. You can buy these swing risers preassembled, or you can buy the flexible pipe and insert ells separately and assemble it yourself.
The preassembled swing risers often have 3 or even 4 ells which makes them much easier to install. You can duplicate this feature by adding street ells to the build-it yourself risers. A street ell is just an ell that has female threads on one end and male threads on the other (see photo below.) I suggest adding a street ell to one or both ends of your swing riser to make it easier to install. The street ells you use should be high density polyethylene, which is black in color and has a slightly oily feel. "Marlex" is a common brand name of high density poly that you may encounter. Do not waste your money on white PVC street ells, they are worthless for swing risers! The threads on high density polyethylene do not seize up like PVC does, which allows the threaded joint to stay flexible.
Do not use more than a 18" length of flexible pipe for your riser! The flow through this pipe is very restricted. Longer lengths cause a high amount of pressure loss and this can mess up the performance of the sprinkler head. If the head is more than 18" away you should run a branch pipe over to it using the same size and type of pipe as the lateral.
When installing the riser do not bend the flexible pipe to help position the sprinkler. Poly pipe has what we call "memory" in the pipe industry- it tries to return to its original shape in a few hours. When it does, it will pull your sprinkler along with it and the end result will be a sprinkler that leans at a weird angle. I have even seen the pipe pull the sprinklers underground! If the pipe is curved when you buy it, work with the curve of the pipe. Twist the ells around on the end of the pipe until the sprinkler is in the position you want without bending the pipe. Cut the pipe length shorter if need be. (I recommend starting with a 12" to 18" length of flex pipe and then cutting it shorter as needed to position the sprinkler.) One more time; do not bend the flexible pipe. Believe me when I tell you that it will save you a lot of headaches later! You do not need to use clamps on the special insert ells that are made for swing risers. These ells are made differently than the ones used for standard poly pipe. They have a self-locking ridge on the ell that seals it and locks the flexible tube on. Most of these swing riser insert ells have spiral barbs, so you need to twist them into the pipe-- just like screwing a light bulb into a socket. You do know how to install a light bulb, right? Finally, you should use Teflon tape on the male threads of the insert ells to seal them. You don't have to use a lot of Teflon on these, a little leak here isn't a huge problem. Again, unless you are a professional pipe fitter, I would recommend that you not use a liquid or paste type thread sealer. See my rant on that topic above in the Simple Pipe Riser section.
OK, I confess it is often not as easy to get the insert ell in as it is to install a light bulb. So if it's cold, the flexible pipe is stiff, and the insert ell just doesn't want to go in, here's a trick-- use KY Jelly on the insert ell barbs. Don't use any other type of oil or soap, they can damage the plastic. Don't know what KY Jelly is? It is a water-based lubricant. Don't head for the hardware store like I did when I was first given this tip. (Now that was an embarrassing incident!) Go to the drugstore or supermarket. Women's hygiene section-- 'nuff said guys?
Drawing of a Flexible Swing riser (above)
Photo of flexible riser pipe and insert ells
A preassembled flexible pipe swing riser attached to a PVC fitting and a pop-up sprinkler.
The riser in this photo is made by Hunter and features 4 ells for ease of installation and added flexibility.
High Density Polyethylene (Marlex) Street Ell
The rigid arm swing riser is the standard riser type used for rotor heads, including the large ones found in parks and golf courses. For small rotors with 1/2" inlets and spray heads I would recommend using the flexible swing joint described above, although there is no reason you can't use a rigid arm swing joint if you want. But for most rotors a rigid arm swing joint is the way to go. The pipe and fittings used to make the rigid arm swing joint should be the same size as the inlet on the rotor.
There are various types of rigid arm swing risers depending on how many ells the swing riser has. The double swing riser has two ells at the bottom of the rigid arm and is pretty much worthless for most situations in my (not so humble) opinion. It allows the head angle to be adjusted, but does not allow the head to be moved up or down. Double swing risers are used primarily for shrub style sprinklers mounted on a pipe above ground. The triple swing riser is much better and is the standard swing riser used by most professionals. The triple swing riser allows the head to move up and down and allows it to be angled in any direction (i.e.; you can install the head at an angle so that it is perpendicular to a slope.) But you still can't move the sprinkler head from side to side with a triple swing riser. That's why I use quadruple swing risers when I use a rigid arm swing riser.
The quadruple swing riser allows the sprinkler head to be moved in any direction. It can be adjusted up or down, angled in any direction, plus it can swing from side to side. For example, lets say you install your lateral pipe parallel to a sidewalk and for whatever reason, the pipe winds up being 10" away from the edge of the sidewalk. With a triple swing riser your sprinkler is also going to be 10" away from the sidewalk unless you install a small branch pipe over to the sidewalk from the lateral. With a quadruple swing riser you simply swing the sprinkler over so it is as close to the edge of the sidewalk as you want it to be. (Again, 4 to 6 inches is the normal distance a sprinkler should be from a sidewalk. Before you ask, no, a 6 inch distance does not cause a dry spot along the edge of the sidewalk.) A quadruple swing riser costs about a dollar more than a triple swing riser, but gives you total flexibility-- which is important if you want a really efficient sprinkler system! A typical rigid swing riser is constructed using a 12 inch long SCH 80 PVC nipple for the rigid arm (generally SCH 80 is gray colored) and high density polyethylene street ells (see photo of a street ell above.) High density polyethylene is typically referred to as "Marlex". Marlex is black in color, softer than PVC, and works better for swing risers than PVC because it has a naturally oily surface. Do not use standard threaded white or gray PVC ells on swing risers! The threads on standard PVC ells tend to stick to each other and keep the swing riser arm from moving as it should. I recommend that you use a small amount of Teflon tape on the male threads, even when using Marlex street ells. By the way, the black plastic used for the Funny Pipe ® risers mentioned earlier are not Marlex! If you can't scratch it with your fingernail, it is not Marlex.
Several manufacturers make preassembled rigid swing risers for sprinklers. Most of these preassembled swing risers are very high quality and use special PVC ells with o-ring sealed swivels built into them. Unlike standard threaded ell joints these swivels allow very free movement of the swing riser and are superior to swing risers made with standard threaded ells. They are often used with the large, expensive sprinklers used on golf course and park irrigation systems. The large, heavy tractor mowers used on parks and golf courses make it essential that the swing risers be able to move freely.
Drawing of a Rigid Quadruple Swing Riser (above)
What if you really need to bend the pipe? There is a very flexible pipe riser product that is now sold at most irrigation supply stores and home improvement stores. It is durable and can be bent to pretty much any position you want. Tie it in a knot if you wish. I have been very pleased with this product so I feel I can recommend it for situations where you need a really flexible riser pipe. It is especially useful for sprinkler replacements. It looks like a flexible electrical conduit. (In fact that's exactly what it is, an flexible electrical cable protector with a length of vinyl tubing inside it!) Don't use it for anything other than small spray head risers. It can't withstand high pressures. I usually put a threaded street ell on one or both ends to make it easier to install.
Flexible Riser. This one is a Cobra Connector brand riser.
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