Revisiting drip irrigation

More on efficiently watering your miniature plants in your garden railway
A half-inch supply line for drip irrigation crosses Abner Creek, attached to a trestle on the author's Rustin & Decrepit Railroad.
Don Parker
The head assembly for the author's drip-irrigation system: (from top down) automatic timer, backflow preventer, straight filter, pressure regulator.
Don Parker
An example of distribution fittings. The fitting on the left, plugged into the ½" main tubing, is a 90° elbow micro-fitting with attached ¼" tubing leading to a section of soaker dripline; on the right is a 1 GPH emitter with a ¼" distribution tube leading to a single plant above the wall. In the foreground (left to right) are: 4-GPH emitter, 2-GPH emitter, punch to perforate ½" main tubing before inserting fittings, and pliers for scale.
Don Parker
A 360° micro-sprayer attached to a ¼" delivery tubing waters a hillside of blue star creeper (Laurentia fluviatilis).
Don Parker
Drip irrigation is so useful in the railroad garden that I wanted to highlight its many advantages again and add tips for the novice. I hope to convince those of you who have not considered using this method to give it some thought. For those who already know the basic facts about drip irrigation or have tried it in a preliminary sort of way, I will share some new ideas that may be helpful in making your system even more functional and indispensable.

Why drip irrigation?

In essence, drip irrigation is a well-proven system for delivering water at a slow, efficient, and accurate rate directly to plants' root zones where it is needed. In contrast, overhead watering wets everything: buildings, track, trains (if they are out), as well as plants. This wets the leaves as well as the roots, setting up conditions that favor fungal diseases of the foliage. Drip irrigation saves water. There is less evaporation and run-off loss compared to overhead sprinkling. It saves time over hand watering. Plants are healthier and more robust with slow, regular, and uniform application of water. Once the system is in place with a timer to turn the water on and off, you can just about set it and forget it. That leaves more time to run trains or tend to other garden chores-even while the garden is being watered!

The head assembly

The heart of the system is located at the water source, either an outdoor faucet or the end of a garden hose. If a timer is being used, it should be located first on the supply line to prevent other sensitive components from undergoing continuous high pressure. Next is an optional backflow preventer to keep contaminated garden water out of your house lines in case of a sudden pressure drop (unlikely). Then follows a filter to keep hard-water sediments and other particles out of the tiny emitter channels. This is essential and should not be left out. With a filter in place, almost any water source can be used without concern for clogging. This can be either a simple straight filter or a "Y" filter that allows flushing while staying in line. Lastly comes a pressure regulator that ensures reliable emitter function-typically keeping pressure between 15-25 pounds per square inch (psi).

A good timer can cost $40 and up. I recommend not getting a discount-garden-center or "big box" store timer. I tried those twice and was disappointed both times. A good timer is guaranteed for two to three years. The other components of the head assembly can cost as little as $13, total.

The delivery system

From the head assembly runs the main, or supply, line(s) to the areas of the garden needing water. For most home gardens, ½" black polyethylene (PE) tubing works well and is tough and fairly flexible. For sharp turns, there are 90° elbow fittings. At junctions, "T" fittings are used. These allow the main line to be laid out in any number of convenient patterns. Typically, the ½" main line is buried and laid in a protected area, such as alongside a walkway or track, where it is easier to remember where it runs, when digging to renovate or add new plants. From the main line, ¼" delivery tubes carry water to the plants. These are typically laid under mulch to hide the tubes.

You can choose from emitters plugged into the supply line (with a delivery tube to the base of the plant), spray nozzles of various types and delivery rates located at the end of a delivery tube, or ¼" soaker drip-line tubes with built-in emitters every 6", 12", or 24". Plug-in emitters are available to deliver one, two, and four gallons per hour (GPH) and are used to supply individual plants. The devices placed at the ends of delivery tubes can be sprayers, dribblers, or mini-jets, with a wide range of water delivery. The soaker drip-lines are probably the most useful in the garden railroad and are adaptable to a variety of applications.

One of my adaptations of drip-line usage involves interspersing ¼" PE tubing with segments of drip-line so that the built-in emitters are positioned near the plants I want to water. This works well for miniature plants, as each in-line emitter puts out only 1/2 GPH. The black ¼" tubing is easy to hide and the emitters work dependably, whether on top of the ground, under mulch, or buried in the soil. The limit for one continuous run of drip-line tubing with emitters spaced every 6" at 20 psi pressure is 15 feet. That amounts to 30 emitters under ideal circumstances. Since I must splice the drip-line using barbed micro-fitting connectors to intersperse various lengths of ¼" solid tubing, I limit each run to no more than 20 emitters to compensate for the reduced flow caused by the tiny fittings.

The diagram illustrates how I have laid out my system for part of the Rustin & Decrepit landscape. At one point, the ½" main tubing crosses a valley attached to a 64"-long bridge/trestle combination.

For the most part, I use drip-lines as I outlined above. I employ mini-jet sprayers for groundcover areas that may get too dry; e.g. a large patch of blue star creeper (Laurentia fluviatilis) located on a steep slope, or areas of moss. One-GPH emitters are positioned for some trees and larger plants, and I have a 4-GPH emitter at my pond to top off the water lost by evaporation. The timer is set for 15 minutes of irrigation every second or third day (adjusted occasionally for the weather and degree of dryness of the soil).

There are fittings for every application to allow you to design a system to match your specific needs. Besides the plug-in emitters, there are microfittings for the 1/4" tubing that come in straight connectors, 90° elbows, "Ts", and four-way connectors. There are mini-jet spray nozzles that cover narrow strip, quarter-, half-, or full-circle patterns. A pop-up riser is available that pops up from 1" to 5" and accommodates a variety of spray nozzles. This discretely hides spray heads so they are less intrusive in the scenery. There are shut-off valves for the ½" main tubing to select or exclude areas to be watered . There are even low-pressure fittings for gravity-fed systems (such as from a rain barrel).

Winter care

In parts of the country where freezing occurs, it is important to drain the tubing as much as possible before the temperature drops. I bring all the head-assembly parts indoors. Then I use compressed air (no more than 40 psi) applied at the supply end to blow out most of the water from the system. All the tubing tolerates freezing temperature well and lasts for years outside. But water accumulating in low areas has the potential of expanding on freezing, cracking the plastic. I then cap the open end of the supply tubing with plastic, held in place with twist ties to keep insects from moving in for the winter.

Supply companies usually offer starter kits with basic components, emitters, and tubing. This is a good way to try out the technique and become familiar with how it goes together. Add drip irrigation to an area of your railway garden that tends to dry out easily and see how your plants respond to this efficient way of bringing water to just where it is needed. I'll bet you and your plants will be pleased, and you can feel good about using this environmentally sound method of
water conservation.

190 Sanhedrin Circle
Willits CA 95490-8753

Rain Bird (most supplies available at Lowes stores)
Irrigation plan for the R&D RR
Download a PDF of the irrigation plan for the author's railroad.

Downloadable File(s)


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