List the plants in your garden on paper. Include trees, shrubs, perennials and annuals. The goal is to set up a complete inventory of plant life within the garden setting. Their location in the landscape isn't important at this step.
Create a diagram of your garden. Make an outline of your property. For separate multiple areas mark the location of each on the diagram. Write in where each type of plant is, or will be, in the garden layout. Including trees and bushes. Knowing where the vegetation is will help you with the next step.
Plan the water use. Now that you have a list of vegetation and their locations, you can estimate the water use for each area of the garden. Different types of vegetation require different amounts of water; the age of the vegetation will also determine water use for the current season. Large trees and shrubs need more water than smaller saplings or seedlings. Newly seeded areas require different amounts of water compared to established areas. Consider the water requirements of each plant. Keep water-loving plants in the same or nearby, locations to each other to avoid overwatering one type of vegetation.
Plan the route of the trunk line. Create a route that takes the shortest route possible to all areas. If you have a single garden space, one line through the center will work. For multi-section gardens, set up the main line to have a minimal footprint on the lawn to avoid becoming an obstruction.
Place the secondary lines. The secondary lines will run off of the main trunk to the plants. These lines should run as close to the vegetation as possible to deliver water to the roots. Use curved pieces, "Y" or "T" connectors when two secondary lines must split off to different areas. This conserves the footprint of the irrigation system similar to the main trunk. Draw in these lines using different colors to designate different water levels or needs.
Select the number of emitters. Use a greater amount of emitters for areas with larger plants or high-usage water plants, such as ferns or fruit. Plants with large root systems, such as trees, will also require more emitters. Plants using lower water flow or occasional watering schedules need fewer emitters after becoming established, such as roses and evergreens.
Select the type of emitters. Emitters are rated by gph (gallons per hour) for water usage. Depending on the soil type, the plant size and the spacing the emitters you need can range from 0.5 gph to 5 gph. Consider a 0.5 gph emitter for perennials in clay or loamy soil. Use 1 gph emitters for shrubs and trees under 15 feet high. Reserve emitters of 2 to 4 gph for larger trees.
Set up zones for irrigation. High-pressure and low-pressure emitters cannot be combined on the same line. If you need more water for a low-pressure area, consider using more emitters spaced closer together. You can rearrange emitters as plants or trees grow to adjust for changing water needs.