Gary Taylor, GT Irrigation Services
Starting up the irrigation system on your sports field(s) can be an easy task or a very labour intensive undertaking. How well you winterized the system in the fall will translate in large part to how well the startup goes. If you blew out the piping network thoroughly with compressed air then pipe breaks should be non-existent or minimal unless we have a severe winter with deep frost. If you blew out the system excessively then there may be sprinkler and valve issues to deal with. For this article, I will be describing starting up sports field irrigation systems. While landscape irrigation involves similar steps, the use of smaller pipe and in most cases polyethylene (PE) pipe makes these areas simpler and more forgiving for startup and blowout.
Sports fields utilize larger pipe sizes and should incorporate the use of PVC pipe and other components associated with a large turf system. PVC pipe has better flow and pressure characteristics than polyethylene and is the preferred choice for large systems. The piping network of a sports field can be divided into two sections:
1. Mainline piping
2. Lateral piping
The mainline is the water carrying pipe from the water source along the side or sides of the field depending on the type and size of field being irrigated. On large fields the mainline may be looped around the perimeter of the field. The lateral or zone piping is installed into the playing area to the sprinklers. Electric valves are installed on the lateral piping directly off the mainline off of the playing surface. In most cases, the mainline is constantly pressurized while the lateral piping is only pressurized when the zone is turned on and the sprinklers are operating.
During startup, the mainline piping is filled or energized first. It is a good principle to install a quick coupling valve (QCV) at the end of each mainline or in the middle of the loop farthest from the water source during the installation of the irrigation system to allow for evacuation of air during filling of the lines in the spring as well as to blow water out of the lines in the fall. Utilizing the opening of a quick coupling valve, e.g. 1” (2.54 cm) diameter, is preferable to utilizing the smaller orifices of sprinkler nozzles. During startup and blow out, a quick coupler key with a hose swivel (and hose if desired) is installed into the valve. Quick coupling valves can also be used for hand watering and filling sprayers. Quick coupling valves should always be installed on swing joints to provide a 3 point swivel connection to the pipe. In the past, assembled galvanized swing joints were commonly used. These should be avoided because the threaded connection will seize up, preventing the swing joint from swiveling and carrying out its purpose of lifting with frost heaval and allowing the valve to push down from equipment. Today, pre-assembled PVC swing joints with ACME threads and o-rings and a brass threaded outlet are available – these swing joints also incorporate a honeycomb sleeve or other form of retaining ring with lugs or ears to allow for the installation of rebar to stabilize the assembly. It is imperative that the swing joint incorporate a brass threaded outlet – a brass quick coupling valve will unthread from a PVC outlet and create a possible safety risk and a lot of water shooting up into the air. Quick coupling valves should always be installed in a valve box or within a concrete collar to inhibit grass growing over and “hiding” them.
Before beginning the startup, it is always a good idea to walk the system and see if there is any visible damage. Check inside all valve boxes to ensure that everything appears intact. If there is ice inside of a valve box that is an indication that there is still frost in the ground and the system should not be started up yet. Though you may not be able to see any of the sprinklers, it is sprinklers that you can see that have heaved with the frost that you are looking for. If a sprinkler is raised or heaved up, grab the head and confirm that it hasn’t separated from the swing joint. If it comes out of the ground with a tug, the sprinkler inlet threads are likely stripped and the body needs to be replaced. If it is firmly attached, gently step on the sprinkler. If the ground is wet, the sprinkler may push back down to ground level as the swing joint does its job. If not, then this head will need to be leveled at some point before mowing takes place.
If the water source is potable water, check to make sure that the backflow preventer and water meter are connected and ready for operation. If there is a booster pump present, make sure all connections are secure and any drains are closed. If you are pumping from a body of water, ensure that the pump is ready for operation. If your system has a master valve and flow sensor, manually open the valve and ensure that the flow sensor internal assembly is securely installed.
Now it is time to begin filling the mainline pipe. If you have a quick coupling valve(s) at the end of the mainline(s), install the coupler key(s) with hose swivel(s). If you don’t, manually open the last electric or zone valve on the mainline(s) or at the midpoint of a looped mainline. Slowly open the main valve to the irrigation system only partially so that you can hear the water “screaming” through the valve. If you have a booster pump do not operate the pump to fill the system. If there is a bypass for the pump, isolate the pump and utilize the bypass. If you are pumping out of a body of water and the pump station has a variable frequency drive, operate the VFD at the lowest speed and only open the discharge valve slightly. While industry practice is to allow the velocity of water in the piping network to be a maximum of 5 ft (1.5 m)/sec. during normal operation, during filling the goal is 1 ft (0.3 m)/sec. or less.
Slowly filling the system will allow all of the air in the pipe to evacuate through the quick coupling valves or sprinklers on the last zone and minimize any potential pressure spikes caused by air compressing in the pipes. Remember the phrase, “Air compresses, water doesn’t.” Air trapped in pipe or that cannot evacuate fast enough can result in pressure surges of 10-15 times the water pressure. These conditions can exceed the ratings of the irrigation system components (sprinklers, valves, pipe and fittings) and cause failure. With pipe and fittings this could result in breaks and with sprinklers the proverbial launching of sprinklers into the air like a rocket.
With a system with quick couplers, once all air has visually and audibly exited the mainline and only water is flowing, open the first zone valve and wait for the sprinklers to pop up and spray only water. Please note that the sprinklers will not operate at pressure because this exercise is to fill the pipe with water and “bleed” off the air. Once the first zone is complete, move on to the next zone. Progress through each zone with the quick coupler(s) installed until all zones have been operated
and only water is flowing.
If there are no quick coupling valves, once the sprinklers on the end zone(s) are operating and flowing only water, turn on the next zone leaving the first zone on. When the second zone sprinklers are operating and flowing only water, turn on the next zone and turn off the first zone. Progress through all of the stations until all zones have been turned on. The key is to ensure that two zones are operating simultaneously to keep the
Once this is completed, close all zone valves and remove the quick coupler(s). Let the mainline build up to static pressure. If there are no visual leaks and there is no sound of water running through the main valve, the valve can be fully opened. The booster pump can now be employed or the pump station set into automatic mode. The master valve can be closed in preparation for operation from the controller. Each station can now be operated at full pressure to check for sprinkler rotation and proper spray pattern. Proper valve operation can be checked at this time as well including pressure regulation readings if pressure regulating valves are installed.
The controller can be turned on at any point in the startup. If you have a maintenance radio for the controller, the controller can be used to progress through the stations. Otherwise it is recommended that you manually turn the valves on during startup so you can visually see the sprinklers bleeding off air and not let the process be dictated by the station timing of the controller.
In the event that you do experience problems, here are some of the common issues and the solution to each. Pipe and swing joint breaks can occur from water left in the pipe over the winter that freezes but they can also occur from very deep frost heaving the ground. If you experience pipe breaks, the quickest and easiest method to repairing them is to install gasketed (eg. HARCO) repair couplings. Once installed and backfilled, the system can be re-pressurized immediately versus waiting the prescribed cure times for solvent welded (glued) fittings. Depending on where the swing is damaged only the top elbow or another portion may need to be replaced if it is the same manufacturer (eg. Lasco, Dura, etc.), unless it is the bottom elbow which would warrant entire swing joint replacement. If there are non-rotating sprinklers, only the internal (or guts) need to be replaced if it is the same manufacturer/model. Please note it is imperative to install the same nozzle in the new sprinkler from the supplied bag or tree of nozzles to ensure matching application rate with the other sprinklers on the station. If a sprinkler becomes separated from a swing joint, only the body may need to be replaced if it is the same manufacturer/model. If you do decide to change to a different manufacturer or model, the entire sprinkler will need to be changed and a nozzle with similar radius of throw/discharge installed to maintain a similar application rate. Electric valves not turning on may be indicative of a solenoid or wire issue. Electric valves not turning off may indicate a diaphragm issue which can be replaced by removing the bonnet only instead of the entire valve.
In summary, the success to starting up an irrigation system in the spring is directly related to the winterizing of the system the previous fall. The key to starting up an irrigation system is to fill the piping network very slowly to allow the air that was pushed into the system in the fall to evacuate as the system is refilled. You should never rush through a startup of a sports field irrigation system – any time save may be more than taken up completing repairs. As the size and complexity of the system increases, this principle becomes all the more important. By following these simple steps, you will minimize inflicting damage to the irrigation system during spring startup. •
Gary Taylor is owner of GT Irrigation Services, an independent irrigation consulting and water management firm specializing in golf and sports field irrigation design as well as central irrigation control for municipalities.