Keeping many pots of flowers and vegetables watered consistently including when you are on vacation requires the installation of an irrigation system. These 'spaghetti' systems are commonly used in greenhouses and to grow garden mums outdoors. Building a similar system at home requires only some simple tools and knowledge of the various components. Drip irrigated crops grow better and with fewer diseases than those either left to nature or overhead watered. In addition to getting better flowers, fruits, and vegetables, you'll waste lots less water since the water goes directly to the root zone where the plants need it. You can even add liquid and soluble fertilizers 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 so that you get the right parts the first time, start by plotting out the containers that you will want to irrigate on a scale diagram. This will make estimating the total amount of tubing, fittings, and emitters much easier. Tubing will need to run very close to these containers. Consider if there is pavement that will need to be crossed. While tunneling under walkways is not always easy, fitting these underground crossings with conduit then feeding the tubing through makes long term maintenance easier. Every system begins at the water source (usually a hose bib) and ends in a plug. Be sure to locate the lowest part of the system and plan to install a drain there to facilitate winterization. If completely drained, all of the tubing minus the filter and pressure regulator can be left in place between the seasons. Commonly available header tubing comes in diameter sizes starting at ½" and on standard size rolls that are 100' and 250' long. The images in this article all use 1" tubing.
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. Checking and cleaning the filter is the only regular maintenance chore. The extremely small channels that regulate water flow are prone to clogging if particles in the water are large enough. Never run your system without the filter in place. These channels are integral to proper water flow. 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 those of us with many containers of flowers and vegetables 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.
Installing your drip irrigation system
In the simplest terms, your system begins with a connection to a water source, then a particle filter and a pressure regulator. The system shown here is designed to run at 35psi, but there are other lower pressure systems on the market. The system shown is installed on an accessory well that is not used for drinking water, systems that run on municipal water or well that supplies drinking water should have a backflow preventer to prevent sucking any fertilizer or pesticides back into the potable water supply in the event of a pressure drop.
Connect the filter assembly with the backflow preventer, timer, hose thread to pipe thread adapter, filter assembly and pressure reducer to your water source. This assembly is your single largest investment in this system and is generally all plastic parts except for the backflow device. Relieve the torque on this assembly by connecting it to a ground post or wall. Connect the mainline tubing to the end of this assembly.
Run mainline tubing wherever you have containers that you want to water. Long smooth curves do not require fittings as the tubing will readily bend, but sharp turns, and splits will require various slip fittings. Fittings come in all sizes and types. Do not kink the tubing as it will interfere with the proper pressure, thus reducing the metered flow. This mainline tubing is also known as orchard tubing and comes in many diameters. As long as the entire system is tight and free of leaks, any shapes will do including loops fed from a "T", and long, single runs to reach containers that are somewhat distant. Install a drain fitting at the lowest point for winterization draining. Pressurize the system to check for leaks prior to the next step. Open a fitting connection at the highest point for this pressure test in order to release air in the system. Once the system is filled with water, closed and pressurized, check for and repair any leaks.
Install an emitter at every container by using the punch tool, then inserting an emitter in the hole. These generally fit snugly and leak very little if at all.
The 'spaghetti' tubing is very narrow and needs to match both the stake that will be inserted into the potting media and the emitter. This narrow tubing comes both precut and in rolls. It also fits very snugly at both ends. It may take a bit of practice to develop a technique to get the tubing installed at both ends. Having the 'spaghetti' tubing slip off the emitter is not unusual. Just push it on more securely and try again.
Getting the plumbing hardware
If you live in an area that has commercial greenhouse, 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 greenhouse, 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. These are all located in Central and South Central PA.
Typical Fittings used to create the mainline system of tubing. These come in all sizes.
Punch tool used to pierce mainline tubing for the installation of the drip emitters. The button in the handle forces the punch out from the tool. Be sure to match the point on the tool to your type of emitter as there are several sizes. This is the only special tool needed.
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. This type of injector does not work well with only a few pots as it requires a relatively high water flow to work properly.
Close-up of the hose bib to filter body adapter with step up fitting to fit the filter body threading. This fitting converts hose-type threads to pipe threads.
Hose bib to filter body to pressure reducer assembly. The lower part of the filter body screws off to allow the filter to be removed and cleaned
One type of programmable digital timer. This screws directly to the hose bib, then the filter assembly screws into it. This version provides for time per irrigation, multiple starts in a single day and specific days on and off.
Note the arrow on the pressure reducer. Filters, pressure reducers, backflow preventers, and fertilizer injectors are all clearly marked with similar flow indicators. They will not work properly if installed backwards.
Standard stainless steel hose clamp used to seal the tube to the insert fittings. Tighten these firmly, but do not over tighten.
Tubing with multiple emitters and spaghetti tubing attached and a 90 degree fitting. Emitters come in various flow rates to allow a single system to accommodate large and small pots.
Goof plug installed where an emitter had been before. These can be removed with a simple twist using a plier.
Ten pack of goof plugs. These are used to fill holes where emitters may have been removed as your system evolves or if a mistake is made. The small end is typically inserted.
Single emitters can be used to feed multiple pots with two and four way splitters. These give added flexibility in systems with very large and very small pots.
'Spaghetti' tubing going into a pot.
Variegated tropical hibiscus with spaghetti tubing and stake.
Operating the system
Emitters are rated by their flow rate per minute or hour. With many different sized pots, you will want to experiment with how long to run the system based on how well your pots are watered. It is not unusual to only need to run the system for 10 minutes twice a day early in the season and twice as long or longer as the plants get larger and demand more. Very large pots (greater than 16") may require two emitters while very small pots may do better sharing a single emitter with a splitter among 2-4 pots.
You can always turn off the main water valve after heavy rains and not disturb your program to keep from over watering.
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 5-10 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 calcium phosphate) that will permanently clog the emitters.
If you remove a pot during the season, simply remove the emitter and install a goof plug.
The 'spaghetti' tubing and mainline tubing used in these systems is reusable for many seasons. At the end of the season and before the first freeze remove the filter assembly from the hose bibb and unscrew it from the mainline tubing. Clean the filter and filter assembly thoroughly and allow it to dry and store indoor for the winter. Plug the tubing where the filter assembly was screwed on with duct tape or something similar to prevent small wildlife from making this a winter refuge. Drain the system completely by opening the valve you installed at the lowest point. If this is a quarter turn valve, leave it in the halfway open / halfway closed position for the winter. Remove and store all of the 'spaghetti' lines, but not the emitters. When you restart the system the next year, start off with no 'spaghetti' lines installed, pressurize the system and look for leaks or cracks. Replace pieces as needed and you're off to another season of easy irrigation. It is not at all unusual to need to replace a few emitters and fittings or to find that your stainless steel clamps need adjustment.
- Irrigation systems tend to develop leaks. Regularly check for leaks at fittings and for popped off 'spaghetti' lines. Do not overtighten hose clamps as this tends to create a future leak or broken fitting.
- There are two kinds of screw together threads that we deal with in irrigation systems: hose and pipe. Hose threads are parallel across the length of the fitting and require a rubber washer in order to seal properly. Pipe threads are slightly flared and seal as they seat into each other. It is impossible to get a good seal when mixing pipe and hose threads. Since we generally go from a hose bib (parallel threads) to pipe threads for the filter body, a special adapter fitting is used to make this jump.
- Always use Teflon tape on pipe threads for a good seal. Applying plumbers silicon paste to the rubber washers on hose bibs keeps the rubber lasting longer and creates a better seal. This same silicon comes in handy when connecting fittings to tubing as it makes it easier to slide the fittings on and creates a better seal.
- Plastic parts crack and break over time. Keeping a few critical parts around such as 90 degree fittings, and "T" fittings (if you used any) will come in handy.
Additional Sources of Information
In print: Trickle irrigation in the United States, NRAES-04. A great primer on trickle irrigation in general.
Suppliers of Irrigation Parts
Martins' Produce Supplies*
625 Britton Rd.
Shippensburg, PA 17257
Nolt's Produce Supplies
152 North Hershey Ave.
Leola, PA 17540
Trickle-EEZ / Zimmerman Irrigation
3550 Chambersburg Rd.
Biglerville, PA 17307
Prepared by Steve Bogash, retired Horticulture Educator. This article is part of the Garden Enthusiast Series (#2)