irrigation systems for home vegetable gardens

Along with careful variety selection, experience, and a number of lesser but contributing factors is their use of drip or trickle irrigation. Drip irrigated crops grow better and with fewer diseases than those either left to nature or overhead watered. In addition to getting better fruits and vegetables, you'll waste lots less water since the water goes directly to the root zone where the plants needs it. You can even add fertilizer through your drip system. Drip irrigation is extremely easy to setup and the parts are readily accessible locally, online, or via catalog. This publication will take you through design, construction, operation and after season storage of a scaleable drip irrigation system

In order to design your irrigation system, you must start with a garden design. Almost any garden including permanent raised beds can be fitted with drip irrigation.

Water Source

Any clean water source is usable for irrigation. Drip systems have a particle filter in order to keep the drippers (referred to as emitters) in the system from clogging. However, this filter can clog if your water source carries too much particulate matter. The extremely fine channels molded into the drip tape are prone to clogging if the particles in the water are large enough. These channels are how the drip tape regulates water flow and are an important part of your system. The system described here uses the same spigot as a garden hose for a water source. Larger systems used in commercial irrigation usually use larger output connections, but even the largest home gardens can be readily served by a standard hose spigot.

If you use a water softener on your home water system, be sure to install a hose spigot before (between the well or incoming water line) the softener to use for a water connection. Water softeners substitute sodium-based salt for calcium and these salts are very toxic to plants. If you have had problems with your house plants and use a water softener, this same advice works for you. Never water plants with "softened" water.

Designing your drip irrigation system

In the simplest terms, you layout the drip lines.

Parts of the System

Basic "H" distribution system showing the hose bibb, filter assembly, and lateral or feeder lines.

Filter assembly

Lateral lines with drip tape attached to quarter turn valves.

Quarter turn valve connecting lateral lines with drip tape. The valve is in the open position. This valve is pressed into the lateral line after using the punch tool.

Drip tape running along a row of looseleaf lettuce.

Getting the plumbing hardware

If you live in an area that has commercial fruit and vegetable production, then accessing the parts for this system will be nearby. Ask neighboring growers about local suppliers of irrigation parts and services. In Pennsylvania, contact your local Penn State Extension office and ask for horticultural information. Ask for assistance in locating your nearest fruit or vegetable educator who will be able to refer you to suppliers. At the end of this publication are some suppliers to get you started locating irrigation suppliers.

End of a drip line showing the drip "tape" folded over several times with a short piece of 1" tubing holding the tape folded.

Fittings used to create the feeder line system. These are all 1" insert-type fittings.

Feeder line to drip "tape" fittings. Those shown are Queen Gil brand, but there are a number of other brands that have similar fittings to accomplish the same goal.

Punch tool used to pierce feeder lines for the installation of the drip tube fittings. The button in the handle forces the punch out from the tool

Quarter-turn drip "tape" fitting shown with drip tape installed

Venturi-type fertilizer injector used to inject liquid fertilizers into the irrigation stream. Be sure to install this before the filter in order to prevent fertilizer particles from causing clogs

Close-up of the hose bib to filter body adapter with step up fitting to fit the filter body threading

Standard stainless steel hose clamp used to seal the 1" lateral tube to the insert fittings

Operating the system

Once you have assembled a system to cover your entire garden and have drip tape running immediately adjacent to the root zone of all of your plants and seeds, it is time to consider how best to water your plants without overwatering them. You also need to consider the capacity of the water source as you do not want to demand too much from your well or water source. Most drip tape uses approximately 5 gallons of water per hundred feet of tape per minute. You can do the math yourself based on most plants need for at least an inch of rain per week which works out to 620 gallons per 1,000 ft². However, the short version of this is that you need to run the system for 8-9 hours per week in order to get that 1 inch of rainfall equivalent. Increase the time to 12-14 hours as large fruited crops such as melons are filling fruit. If you are going to do your own math, be sure to allow for walkways, this reduces the amount of water needed by about 50%.

If you have a low capacity well and are concerned about over taxing your water source, use the quarter turn valves to create zones by turning particular areas on or off and using the system daily covering only a small area. Inserting a timer between the hose bibb and the filter body will greatly assist you in running the system on a daily basis.

One of the true beauties of a drip irrigation system is the ability to add liquid nutrients (fertilizers) directly through the system. This can be done anytime during the growing season using a venture-type fertilizer injector (see photo). Be sure to install the injector between the water source and the filter so all particles get removed rather than clogging drip emitters. After injecting any fertilizers into a drip system, run clean water through the lines for 15-20 minutes in order to flush out any minerals that may clog the emitters later. Never run a fertilizer containing phosphorus before or after a calcium fertilizer without flushing the lines completely as you will create a precipitate (hard, insoluble substance) that will permanently clog the emitters.

Turn off lines or areas as they are harvested, clean the mesh filter regularly, and keep an eye out for serious leaks. By nature, these systems tend to drip a little at the fittings. If the flow is slow, don't mess with the drips as they usually get worse as you "play" with it to eliminate the problem and the leaks will often go away as the system runs. If a drip line develops a leak or hole along its length, either replace the line or use one of the many fittings as a repair. A serious hole under plastic mulch will probably require replacing the drip tape. Rodents are the usual cause and replacing the drip line is the best solution. Consider poison baits and traps to prevent additional damage to your plants and drip lines.

System Maintenance

To fix a hole in a drip line under plastic mulch:

Disconnect the line from the valve.
Attach the new drip line to the old line by a simple knot.
Pull the old line out from the plastic mulch with the new line attached.
Untie the knot, connect the line to the valve, fold the end and clamp it.
Start irrigating again.

If you make a connection using the insert-type fittings that is incorrect, be ready to replace that fitting rather than reuse it. It is very difficult to remove these fittings without cutting. Once the inserts are damaged, they usually leak regardless of how well you clamp them to the lateral line.

Winter Storage

The flat tape used in these systems is considered disposable at the end of the growing season. Due to the low cost of the tape per foot and likelihood that some damage or clogging has occurred to the tape, it is strongly recommended that you do not attempt to use it a second season. Find other uses for it or dispose of it. Remove the filter assembly from the hose bibb and unscrew it from the lateral or feeder lines. Clean the filter and filter assembly thoroughly and allow it to dry and store indoor for the winter. In order to save your laterals / feeder lines and related fittings; open all of the quarter turn valves and remove one of the end caps. Raise the assembly of laterals, valves and assorted fittings until all the water has drained out. Store this assembly by attaching it to a fence or the wall of a garage with the opened end at the lowest point. Leave all valves in the full open position in order to prevent any freeze cracking from any residual water in the system.

When you restart the system the next year, start off with all the valves closed, pressurize the system and look for leaks or cracks. Replace pieces as needed and you're off to another season of easy irrigation.

Additional Sources of Information

Online

North Carolina State University Cooperative Extension #8033 Using Plastic Mulches and Drip Irrigation for Vegetable Gardens.

You will also get numerous "hits" to a search for drip irrigation or trickle irrigation with fact sheets and suppliers.

Suppliers of Irrigation Parts

Suppliers marked with an asterisk* will accept telephone orders and ship.

Martins' Produce Supplies*
625 Britton Rd.
Shippensburg, PA 17257
717-532-5918

Nolt's Produce Supplies
152 North Hershey Ave.
Leola, PA 17540
717-656-9764

Trickle-EEZ / Zimmerman Irrigation
3550 Chambersburg Rd.
Biglerville, PA 17307
800-672-4700

Prepared by Steve Bogash, retired horticulture educator.