How do I set up drip irrigation for a garden?

Start with a plan, not a roll of tubing

A garden drip system is a supply line from the spigot, a few parts that protect it, and tubing or emitters that put water at each plant's roots. Plan it on paper first: sketch the bed, mark each plant, and measure the run from the spigot. Group plants that need similar amounts of water, because zones should group plants with similar irrigation needs together.^[2]

The payoff is real. Microirrigation systems use 20 to 50 percent less water than conventional sprinkler systems.^[1] The water goes to the soil at the plant, not onto the leaves, so there is less runoff and evaporation.

Choose drip line or point emitters

Drip line emitters are tubes with evenly spaced emitters that water at a uniform rate.^[2] They suit a row of vegetables or a narrow bed, because every plant along the line gets water. Point-source emitters discharge water from a single point that can extend from a long pipe, which suits containers and scattered plants.^[2]

For a vegetable garden, the count is simple: flower beds and vegetable gardens may only need one emitter per plant.^[2] Shrubs often require one or two emitters per plant, depending on their type, size, and age.^[2] Check the flow rating on the package so every emitter in one run delivers the same amount.

The parts at the spigot

Between the spigot and the tubing you want a filter, a pressure regulator if your pressure is high, and ideally a timer. In most kits they screw together in that order, so follow the instructions in yours.

• Filter. Emitters can also become clogged by particles that enter the irrigation system. Use filters to block these particles, especially in systems fed by non-potable water, and clean them frequently.^[2]
• Pressure regulator. Microirrigation is a low-pressure, low-flow-rate type of irrigation.^[1] EPA says a contractor will also check your incoming water pressure to see if it is higher than recommended for the microirrigation system, to determine if a pressure regulator is needed.^[2] Read the pressure rating on your tubing and emitters and compare it with your home's.
• Timer. Virginia Cooperative Extension agent Shawn Jadrnicek says it's best to use some type of automated irrigation system to make sure you're giving your vegetables the correct amount of water at the best time.^[3]

If the system connects to anything beyond a hose spigot, backflow protection comes into play. Depending on your source of water, your system may need filtration, or connection to a backflow preventer may be required to avoid contaminated water entering the potable water system.^[2]

Lay it out and set the schedule

Run the tubing on the surface along the bed and keep it out of walkways. Tubing should be positioned so as not to cause a tripping hazard.^[2] Mulch over the line is fine and helps hide it. Burying lines means digging, and Virginia 811 says that any time you put a shovel in the ground you need to contact Virginia 811, because many utilities are buried just a few inches below the surface.^[4]

Drip schedules run short and often compared with sprinklers. Jadrnicek's guidance: "I would water once or twice a day for a longer period of time with loam soils and up to 10 times a day for a shorter period of time with sandy soils."^[3] Watch the plants and the soil a few inches down, then adjust.

Keep it running

Weeds can still grow into the emitters, causing clogs and reducing efficiency.^[2] Pull them at the roots and clean the filter often. Before the first freeze, the system should be flushed of standing water, to avoid the water lines freezing during winter months and causing cracks in the pipes.^[2] For the in-ground version, see how to winterize a sprinkler system.

Stop and call a pro if

• You want to tie into house plumbing or an existing in-ground sprinkler system. Prince William County says all lawn irrigation systems require a cross connection device to prevent the backflow of water from the lawn irrigation system into the structure's potable water system.^[5] Chesterfield County says backflow prevention assemblies on irrigation systems are required by law.^[6]
• The plan means trenching. Call Virginia 811 first, or let a licensed contractor handle the digging.
• Your water comes from a well or other non-potable source and you are unsure how to filter it.
• The bed is large or sloped, and flow drops off at the far end of the line.
• Water shows up where it should not, such as near the foundation or a wet spot in the lawn that never dries.

Getting help in Virginia

Costs and the decision to hire are covered in how much drip irrigation costs in Virginia and whether to hire someone to install it. More is in the irrigation answers and the irrigation guide.

When you would rather have it done, describe the job once and licensed local contractors quote it.