Most superintendents have replaced irrigation sprinklers, a few have installed them. Several important criteria will insure the sprinkler can successfully deter all the damaging external issues they are exposed to. Its worth reviewing these tips every now and then.
If not installed properly, the sprinkler will likely suffer premature death or worse, be broken from its swing joint. Proper sprinkler mounting is not hard if you know the basics. The Broken Swing Joint picture shows results of an improperly mounted sprinkler.
The valve to operate the sprinkler is in the base of the sprinkler, the pipe below is always under pressure. If the sprinkler is snapped off the swing joint you have a torrent of water until somebody notices and shuts down the mainline. Not a desirable condition.
Remember, your irrigation system is a complex mechanical system installed in a harsh outdoor environment. The equipment is designed to take the beating, but only if correctly installed. Well designed and installed irrigation systems will deliver decades of good service.
The Basics of Golf Sprinkler Mounts
See the two Installation Details. We’ll use this as the basis for the rest of the discussion.
Generally there will be PVC, but the use of HDPE is growing. Both pipe types work well. Pipe can be as small as 1½” or as large as 12”. The pipe will provide water for the sprinkler and is integral in providing support.
Pipes must be installed at an acceptable depth. Not only to protect the pipe, but to serve as a good foundation for sprinkler mounting.
Pictured in Installation Detail 1 is a saddle fitting on a HDPE pipe. The most common way to make a connection on HDPE pipe. Note, the tee outlet is aimed upwards but an elbow is installed to the side for the swing joint. The equipment to install the saddle on HDPE usually makes it difficult to install the outlet to the side.
PVC pipe can use saddles too, however they are not
recommended. More commonly a PVC or iron service tee is installed as pictured in the Installation Detail 2.
Some thoughts on PVC pipe service tees:
1. Solvent weld fittings are generally not recommended. They can be used successfully on PVC pipe 2” or smaller. For larger pipe, use a press-on gasket type fitting. Why? It is difficult to solvent weld larger pipe (introduces errors causing failures) and the connection will lack give for expansion and contraction as soil temperature changes.
2. Iron fittings are recommended. Even though they cost more, in the end they are worth every penny! Why? PVC fittings have difficulty resisting repeated flexing due to pressure surges. Cracks can happen in the crotch of elbows and tees causing a leak. Iron fittings are able to handle those surges.
3. The service tee opening must aim to one side or the other of the pipe. Not up. Why? Half of the swing joint function is ruined if not coming in from the side. Given a heavy impact, the pipe fitting and pipe itself may be damaged.
The Swing Joint
All large in ground sprinklers must be installed on acceptable swing joints. Most anything on a golf course is considered a large sprinkler.
The swing joint serves many purposes:
- Supplies water to sprinkler- must be sized large enough for unimpeded flow
- Protects the pipe and service fitting- absorbs impact from the surface and mounts sprinkler to side of pipe thus displacing impact into the soil and away from the pipe
- Allows easy height adjustment for the sprinkler- easy adjustment of the lay arm to mount sprinkler at proper height
- Allows easy leveling of the sprinkler- lay arm and the top and bottom elbows give full adjustment to level the sprinkle at proper angle
- Act as a shock absorber for the sprinkler and pipe- lay arm and elbows absorb and redirect surface impact
Older swing joints may be a collection of steel elbows and nipples. They are not as easy to work with as modern unitized PVC swing joints made of gasket connections.
Unitized swing joints are not designed to be tightened but to freely rotate. This allows easier readjustments years later. Readjustments are necessary because soil builds up, shrinks away, or the sprinkler may tilt.
Note the installation details. To get the impact protection desired, the lay arm angle must be between 30 and 45 degrees.
Golf sprinklers do a remarkable job lasting decades given the punishment they endure. To help them handle their beating please install them per the engineer’s specifications! Doing so allows the sprinkler, swing joint, and surrounding soil to handle all the impacts that will happen. Note the installation details.
Notice the relation of the sprinkler top flange and soil level. Rain Bird sprinklers are engineered so the outer rim of the flange is slightly below the soil. Doing so engages the surrounding soil as part of the impact protection.
The top flange is designed to minimize and deflect impact energy. Impact happens when mowers and carts run over sprinklers. The deeply chamfered edge of a Rain Bird sprinkler top flange is described as having a “speed bump “ design. Other sprinklers have a more square edge thus are more susceptible to impact damage. See the Rain Bird Rotor picture.
See the Proper Sprinkler Setting picture for a top view of a well set sprinkler. A properly installed sprinkler and swing joint will handle most impact events with no damaging effect. Otherwise, bad things happen. When installed too high:
- Impact energy must be handled fully by the sprinkler and swing joint. The soil
around the sprinkler is not engaged. Over time the occurring micro damages will eventually cause the swing joint or fittings to crack. See picture Too High.
- The exposed edge of the sprinkler will create a catch point for equipment to snag. Either first or repeated impacts will cause a fitting failure. See picture Side Impact Break. In either case, there is a leak.
What about being installing too low? See picture Too Low.
- A depression is created, which will gather debris and cause a bump when run over by mowers and carts. Not a killer, just a maintenance headache.
- The sprinkler will not be able to clear the surrounding turf. Cause the stream to be deflected which ruins your distribution uniformity or “coverage”.
A sprinkler must be level with the soil so the stream is not angled up or down. Your distribution uniformity is destroyed when unleveled. Buy a small surface level at the hardware store!
When the sprinkler become severely unleveled, the high edge becomes a snag point for equipment. Expect the sprinkler to be broken off it’s swing joint.
The question always comes up about setting sprinklers on slopes. There is no perfect answer other than, move the sprinkler to flat ground. Unfortunately golf courses have lot of sloped areas.
The best answer is to slope the sprinkler at half the angle of the slope. Mounting even with the slope causes the uphill stream to point too high in the air. Mounting at level means the uphill stream will aim into the slope. Neither are good situations for irrigation uniformity.
When sprinklers are replaced both height and levelness have to be set. This is especially
important when different sprinklers are installed. If brand or models are being switched, the height of the sprinkler may be different. Simply digging around the sprinkler enough to unscrew it and screw on the new one will cause the new sprinkler to be too high or low. A bigger hole is necessary so the lay arm of the swing joint can be adjusted.
It is also important to note if the swing joint has Iron Pipe Thread (IPT). All new sprinklers will have an ACME thread. See picture ACME Adapter. If the swing joint is not being replaced, an adapter must be added. This adds about ¾“ to 1” of additional height. This is precisely why the sprinkler in the picture Too High is mounted so high. Again, the swing joint lay arm will need adjusted to lower the sprinkler.
The benefits of ACME threads are wonderful. That’s why the sprinkler manufactures converted to ACME years ago. ACME eliminates the common over tightening problem and makes for easy adjustment later.
Hand tighten ACME threaded fittings. You do not need a wrench. The suggestion is to fully tighten by hand, then “back off” a half to full turn. ACME threads are primarily sealed by an O-ring, not engagement of the threads.
Do not use Teflon paste or tape on ACME threads.
In conclusion, properly mounting a sprinkler can determine the wear and life span. Avoiding mistakes like mounting too high or too low can create the proper wear of a sprinkler. Remember that every brand is different. If you change brands more adjustments to the system will need to be made. Good installation leads to great irrigation!