End guns can provide economical and effective irrigation coverage if designed and selected properly. The application under the end gun should be matched as closely as possible to the application under the system. This requires determining the gallonage of water needed for the effective end gun radius desired and selection of the proper end gun and nozzle size. It may also be necessary to incorporate a booster pump to optimize the end gun effectiveness on low pressure systems.
The following information is provided to assist you in the design and selection of end guns and booster pumps.
All end guns require a minimum pressure for proper operation. Systems with low pressure sprinkler packages will require a booster pump for proper operation in most instances.
Effective range is also an important factor in end gun application. Range will be dependent on the end gun pressure, model and nozzle size of the end gun. Typical effective ranges (in meters) of end guns at 40 PSI, 50 PSI, 60 PSI and 70 PSI are shown in this figure:
The effective ranges shown will not necessarily be the ranges that are published by the end gun manufacturer, but is the distance that the amount of water applied closely matches that under the system. Even though water application may extend past this point, it will progressively be less than that under the system.
Determining the specific end gun and nozzle for a system requires finding the gallonage necessary for the end gun. This is based on three factors – system length, system gallonage, and the effective end gun range desired.
Once the end gun gallonage has been determined, an end gun and nozzle size must be selected to match the gallonage requirement.
If this system is a low pressure system, a booster pump will be required to increase the pressure.
Selection of the proper booster pump is dependent on the end gun gallonage required and the pressure needed to provide the gallonage and range. The pump that has the capacity for the gallonage needed must be used. Knowing that gallonage, you can determine the amount of pressure boost that the pump will provide. This value must then be added to the end pressure of the system to find the total pressure available from the pump.
Plumbing from the pump to the end gun includes various lengths and sizes of hose along with a valve and miscelaneous fittings. Depending on these variables, there will be a certain amount of friction loss (pressure drop) from the pump to the end gun. This loss must be subtracted from the pressure available at the pump to determine the actual pressure available at the end gun.