How to Lay Out a Sprinkler System

If you live where watering is a season-long or year-round affair of
hoses and sprinklers, consider a permanent sprinkler system. Whether
it's spray or drip, manual or automatic, a customized sprinkler system
saves time and possibly even water.

Instructions

1. Make a scale drawing of your yard that includes all areas that need watering. Include key features such as the house, driveway and paths, as well as trees, shrubs, planting areas and lawns.

2. Sketch out, with dimensions, all areas that need their own watering schedule and whether they are best served by spray or drip. Drip examples might include the vegetable garden, droughttolerant shrubs in full sun and drought-tolerant shrubs in shade. Use spray sprinklers for lawn areas or ground covers.

3. Assess how much water pressure and flow is available on a sustained basis from your main water supply. Test a spigot near the supply line that you'll be using. Measure the pressure with a pressure gauge, and measure the flow by counting how many seconds it takes the wide-open spigot to fill a 5-gallon bucket, then divide 60 by the number of seconds, then multiply by 5, the size of the bucket. For example, if it takes 20 seconds to fill the bucket, divide 60 by 20 and then multiply by 5 to get a flow rate of 15 gallons per minute.

4. Figure out how many sprinklers are needed for each area and how much water each sprinkler needs to operate correctly. Add up the amount of water required for each area on your drawing and compare that with the total amount available. If the water supply is sufficient, each area with similar water requirements becomes one circuit, and each circuit is controlled by one valve.

5. Choose between electric valves, which are operated by a timer, or manual valves, which you turn on and off. Inline valves are installed below grade, but require an upstream pressure vacuum breaker to protect household water from backwash. Valves that include an integral antisiphon device must be installed 12 inches (30 cm) above grade.

6. Connect to the water supply via an exterior hose bib, or tap into your water line as it emerges from the meter, whether that's in the front yard or in the basement (in cold climates).

7. Lay out pipes or tubing, dig trenches and, working downstream from a valve, assemble them. Use PVC pipe where soil doesn't freeze; use polyethylene pipe where it does. Insert T connectors and flexible riser pipes where you want sprinklers to be located.

8. Flush dirt from all circuits, cut the riser pipes to length and attach the sprinklers. Operate the circuit, check for leaks or other problems, then refill the trenches.

Tips & Warnings

• An automated system can greatly enhance the convenience of a sprinkler system and keep your garden thriving even while you're away.

• Plan spray systems so that spray from each sprinkler reaches each adjacent sprinkler. If the site is windy, a slight overlap is a good idea.

• If you live where soil freezes, be sure to install a system drain, or better, a device that permits the pipes to be blown out.

• Check with utility companies before trenching. Call [phone]. (In Maine, Massachusetts, New Hampshire and Rhode Island, call [phone].)