Best Drip Irrigation System for a Vegetable Garden: Kits by Size

The Best Irrigation System for a Vegetable Garden

For most home vegetable gardens the best irrigation system is drip: low-pressure tubing that releases water through emitters at the base of each plant. Colorado State University Extension puts drip above 90 percent efficiency, while sprinklers land at 50 to 70 percent, and Iowa State University Extension reports that drip uses 30 to 50 percent less water than sprinklers or other methods. The leaves stay dry, which matters for disease-prone crops, and the paths between rows stay dry too, so fewer weed seeds sprout there.

The two alternatives still have a place. A soaker hose costs little and suits one short bed. A sprinkler covers a newly seeded block quickly. The table shows where each one fits.

System	How it waters	Fits best	Main limit
Drip (emitters or in-line tubing)	Metered drops at the root zone, 20 to 30 psi	Raised beds, block plantings, mixed crops	Needs a filter and regulator, clean water
Soaker hose	Seeps along its whole length	A single short bed	Output varies along the hose, so keep runs to 25 feet or less
Overhead sprinkler	Wets the whole soil surface and the foliage	Large seeded areas	50 to 70 percent efficient, more weed germination

Steady moisture at the roots also helps crops such as tomatoes and peppers that are prone to blossom end rot when soil swings between wet and dry. The rest of this guide covers what a drip kit has to contain, how to size one, and how to run it.

What a Drip Irrigation Kit for Vegetable Gardens Must Include

Kits differ in tubing length and emitter count, but the parts between the faucet and the bed should be the same in every one. Colorado State puts typical household water pressure at 50 to 60 psi, and drip components are designed to run at around 20 to 30 psi. Utah State University Extension gives the working range as 10 to 30 psi, and the hose-end regulator in Colorado State’s example garden reduces pressure to 25 psi. A regulator is the part that closes that gap.

The filter matters just as much because emitter openings are tiny. Colorado State recommends a 150 to 200 mesh screen for relatively clean municipal water. Water from wells or ponds can carry larger particles and calls for more elaborate filters and more frequent cleaning, so if you feed the system from rain barrels, plan to rinse the screen often.

Before you buy, read the parts list for these items:

• Backflow preventer
• Filter, 150 to 200 mesh
• Pressure regulator, for example a 25 psi model
• Half-inch polyethylene mainline
• Emitters or in-line emitter tubing
• Stakes, end caps and a few spare couplings
• Timer, included or sold separately

Entry-level kits sometimes leave out the regulator or the filter to reach a lower price. Add the cost of those parts back in when you compare two boxes.

Hook-Up Order at the Faucet

The order of the parts is fixed, and Colorado State lists it as backflow prevention device, control valve, filter, then pressure regulator.

1. Thread the backflow preventer onto the faucet.
2. Add the timer or control valve.
3. Attach the filter.
4. Attach the pressure regulator.
5. Connect the half-inch mainline and run it to the beds.

The regulator goes last so that every part downstream of it sees only low pressure. On a slope, pressure changes with height, and Colorado State’s rule of thumb is to add 5 psi of operating pressure for every 10-foot rise above the connection to the water source.

How to Size a Drip System to Your Beds

Square footage alone does not size a drip system. Two limits do: how much water the mainline can carry and how long it can run. With half-inch mainline, Colorado State caps a single zone at 200 gallons per hour and 200 feet of mainline. Stepping up to three-quarter-inch tubing raises the ceiling to 480 gallons per hour per zone.

Emitters are sold by flow rate, typically half a gallon, 1, 2 or 4 gallons per hour. Add up the emitters you need and multiply by the rating. A 4 by 8 foot raised bed with four lines of in-line tubing and emitters every 12 inches has 32 emitters. At 1 gallon per hour each, that bed draws 32 gallons per hour, so six such beds draw 192 gallons per hour and fill one half-inch zone.

Garden	Emitters at 1 gph	Flow	What to buy
One 4 by 8 foot bed	32	32 gph	Small single-zone kit
Three 4 by 8 foot beds	96	96 gph	Single-zone kit with extra tubing
Six 4 by 8 foot beds	192	192 gph	Single-zone kit at its limit, or two zones
More than six beds	Over 200	Over 200 gph	Two zones on a splitter, or three-quarter-inch mainline

Measure one more number before you shop: the distance from the faucet to the farthest bed. If the route is longer than 200 feet, a boxed kit will not cover it in one zone. For a garden of one or two beds, a small-garden drip kit is usually the better fit than a large expandable set.

Match the Emitter Style to the Crop

Vegetable gardens mix crops that sit 3 feet apart with crops sown 2 inches apart, and one emitter style rarely suits both. Iowa State’s rule is to space emitters every 12 inches, or for widely spaced plants to give each plant one emitter.

Point emitters punched into blank tubing work for tomatoes, peppers and squash, where the water should land at each root ball. Emitters can also sit on the ends of quarter-inch microtubes, which is how a drip line reaches pots and grow bags; Colorado State describes drip as well suited to container plants. In-line emitter tubing has the emitters built in at preset intervals. Quarter-inch tubing typically comes with 6, 12 or 24 inch spacing, and half-inch tubing is sold with 9 to 48 inch spacing. Choose the spacing by soil: 12 inches apart in sand, 18 inches in loam and 24 inches in clay, because water spreads sideways farther in fine soil.

Soaker hoses and laser-drilled tubing have holes but no metering emitters. Colorado State describes them as less satisfactory because the amount released varies along the length. Kits that include both point emitters and in-line tubing give you the most room to rearrange beds between seasons.

Drip Irrigation for Carrots and Other Row Crops

Closely sown crops such as carrots, beets, lettuce and bush beans need a continuous moist strip. In a raised bed, Colorado State spaces drip lines 12 inches apart, which gives a 4-foot bed four lines.

Carrots are the hardest test of a drip layout. Utah State University Extension notes that the seed is planted a quarter inch deep and takes 14 to 21 days to emerge, and the soil surface has to stay uniformly moist the whole time. Sow the rows directly beside the drip lines and run short cycles daily until the seedlings are up. Utah State recommends drip for carrots where possible and sets rows 12 to 18 inches apart, which lines up with one drip line per row.

How Long to Run a Vegetable Drip System

A vegetable garden needs about 1 inch of water per week according to Iowa State, and Colorado State estimates use at around a quarter inch per day in the growing season, depending on temperature, wind and crop stage. Start the season by soaking the bed to a depth of 10 to 12 inches. After that, Iowa State suggests replacing what the plants use, usually every one to two days for a few hours.

A battery timer at the faucet handles this without daily attention. Use the timer to hold the interval steady and adjust the run time as the weather changes; a summer watering schedule shows how the interval shifts in heat. Dig beside a plant with a trowel after a cycle. If the root zone is still dry, lengthen the run.

Two maintenance jobs keep emitters working. Flush the mainline before the first watering in spring by opening the end caps and letting water run clear. Before hard frost, drain the lines; if you blow them out with compressed air, Iowa State warns that pressure above 30 psi is likely to damage emitters.

Quick recap

• Drip tops 90 percent efficiency; sprinklers reach 50 to 70 percent
• Every kit needs a backflow preventer, a 150 to 200 mesh filter and a regulator that brings faucet pressure, often 50 to 60 psi, down to 20 to 30 psi
• One half-inch zone carries up to 200 gallons per hour over 200 feet of mainline
• Emitter spacing: 12 inches in sand, 18 in loam, 24 in clay
• For carrots and other row crops, lay in-line tubing with lines 12 inches apart