How to Design a Garden Water Sprinkler System

Draw a plot plan for your entire lot or the area, such as the front or back yard, that you want to irrigate with the sprinklers. Include the measurements of the area on the plan so that you can correctly size the circuits and sprinkler fixtures. Indicate any slope in the grade over 10 percent; you need to consider the runoff when when choosing the equipment for that location.

Diagram your plantings on the plot plan. It is important to distinguish in the plan between lawn, trees, shrubbery, flowers and vegetables, because each type of plant has specific watering requirements.

Mark the locations of the water sources on the plan. You need to install the manifold near a water source or you will have to plumb from the source to the desired location. You need to consider the length of the source run when computing the size of the sprinkler circuits.

Divide the plan into circuits, with each circuit representing a group of sprinklers controlled by a single valve in the manifold. When designing the circuits, consider the plants and their water needs, the exposure to sun and the size of the area. Lawns have different watering requirements than most other plants in your landscape, so they should have circuits of their own. Shrubbery is watered less frequently than flowers and vegetables. The plants on the sunny side of your lot will dry out much faster than those in the shade, so your system should water them separately.

Plot the locations and types of sprinkler heads that you will use to irrigate specific areas. Each type of fixture has a maximum range to which it will spray water. Lay out your sprinklers so that the spray of adjacent sprinklers overlaps. A good rule of thumb for computing overlap is that the spray of one sprinkler should nearly reach the head of its neighbor. Sprinkler heads also provide different shapes of spray patterns that enable you to water the plants but avoid soaking the siding at the same time.

Verify that the water pressure and flow are sufficient to operate the equipment you want to install on a circuit. Consult the manufacturer's data sheets for each piece of equipment, and total the gallons per minute, or GPM, required per fixture; then add 10 percent to this total for pipe runs and other routing equipment. Ensure that the GPM of your system is sufficient to operate each circuit.