Drip Irrigation System for your Garden

By Robin Tower

Find out how to install your own drip irrigation system for your conifer garden.

Get ideas on installing a drip irrigation system in your garden
Get ideas on installing a drip irrigation system in your garden

First I should explain that I am not an irrigation expert. What follows are my observations from my own experience with drip irrigation. I expect that when you think of a drip irrigation system you think of neat orderly rows of tomatoes or beans. It’s hard to imagine it applied to a meandering, random set of conifers in a large area. But drip irrigation works just as well in that situation!

The advantages of watering with drip as opposed to sprinklers or buckets are several. A large amount of the water delivered through a sprinkler is either lost to evaporation or lands between plants, thus promoting the growth of weeds. Buckets are back-breaking, and deliver the water too rapidly, so that much of it is wasted. A drip is like a fine rain soaking into the root system over a set time, perhaps an hour or two. Therefore, it is both less labor intensive, and much more efficient.

Sketching the Drip Irrigation System Out

Figure 1 showing a drip irrigation system of a garden
Figure 1 showing a drip irrigation system of a garden

To get your project started you will need a rough sketch of the area to be watered. It might look something like Figure 1. Seeing the property from the air as it were, allows you to analyze how it might best have watered delivered through pipes.

In Figure 1, I show a display bed of conifers and perhaps other plant material that is about 50 ft. long and of varying depth. It contains about 42 plants of diferent sizes.

Secondly, you will need to have an idea of how many gallons per hour your water source can supply (its flow). This is an easy job – turn the hose on and fill a 5 gallon bucket. How much time did it take? Mine took about 56 seconds. So it will supply about 11.2 gallons every second (So, it will supply one gallon every 11.2 seconds, or 321 gallons per hour.) This number will determine how many plants you can water at one time.

The emitters you will use to supply water to each bush will put out 1 gallon per hour. I usually use one emitter on a bush less that one inch in caliper, and increase by one emitter for every caliper. So, a bush with a trunk of 3 inches in diameter would have 3 emitters, and get 3 gallons of water an hour.

Determining the Pressure in the Drip Irrigation System

The third piece of useful information you will need is the amount of PSI (pounds per square inch) of water pressure your system provides. You can buy a gauge to measure this quite inexpensively from an irrigation supplier. Screw it onto the end of a hose, and when you turn the water on, and voila! Your pressure is measured. I use 2 water sources, my own well and pump, and a municipal source.

I found that the municipal system had a lot more pressure (about 45 PSI) than my well (15 PSI). Typically, the water tubing which delivers the water to the plant is designed only to handle a maximum of 30 PSI – so, if your source is higher than that, you will need a pressure regulator to reduce the water pressure going into the system.

Assembling the Drip Irrigation System

Figure 2 showing the garden's main line connected to the water source of the drip irrigation system
Figure 2 showing the garden's main line connected to the water source of the drip irrigation system

Now that you have gathered information, it is time to put it all together. Draw a line (the main line) connecting in the most logical order possible your conifers or other trees to be watered. (Figure 2) The line does NOT have to run from one to the next, but simply near them. The start of the line should be near your water source.

With any luck, it will slope downward from there towards the end of the line, although this is not completely necessary. You can plan on more than one main line and connect them with a T or Y connector. However, if your flow as measured above is 300 GPH, then remember that you can only put 300 emitters on one main line. You will use hose connector fttings for the beginning and end of the line.

Next we will get the water to the bushes from the main line. A branch line is used for this, usually ¼ inch tubing. The tubing connects to the main line with a ¼ inch transfer barb. The emitter fits into the ¼ inch tubing connecting with its own transfer barb on the emitter.

Emitters and Tubes for the Irrigation System

Figure 3 demonstrating the position of emitters of a drip irrigation system in the garden
Figure 3 demonstrating the position of emitters of a drip irrigation system in the garden

There are several diferent types of emitters available. What you MUST have is a pressure-compensating emitter. These will ensure that you get the same amount of water delivered through each emitter, even if your terrain is uneven. I have used the CETA in-line emitters. These come on stakes so that they can be put securely in the ground near the root ball of the plant. They can be used in tandem, so that you can put several around the base of a tree (See Figure 3).

Since I have 42 plants, and need to use an average of 3 emitters per plant in this imaginary garden, I am well within the maximum of 321 emitters per line. If I had more plants, or more areas to water, I would make each area a separate zone, with a separate connection to the water source.

Final Touches around the Conifer Garden

You will want to secure the main line to the ground with landscape staples. At some point, the main line should be covered with mulch or buried a few inches below ground by trenching. This procedure will keep the plastic from degrading in the sun. It is not necessary to do this immediately; in fact, I have waited a year to do mine. That way, if there is a problem with emitter placement or a misplaced hole punched, I can spot it and correct it without digging up the line.

Lastly, we will connect our main line to a water source. The connections between main lines are all hose threaded, so that there is no real plumbing involved. Simply push the female hose end connector into the main line, and you are ready to hook up the system!

However, there are several pieces and they need to be put together in the correct order. Closest to the water source, you will need a screen flter, particularly if you are using well water. If you are pumping from a pond you may need a heavier duty flter perhaps a Disc flter. Debris in the line will clog the emitters and should be avoided at all costs!

Other Accesories for a Drip Irrigation System

Next in the order is the PSI regulator. Then the mainline tubing is connected with a female hose start. (See Figure 4), and be sure to put end caps on each main line, or the water will simply flow right on through! Two important notes: I found that punching holes in the main-line tubing did not work well after the tubing had warmed in the sun. The punch merely bent the tubing without leaving a clean hole. You will want to purchase a pack of goof plugs in case this happens to you. They are useful as well to stop up a hole you may punch inadvertently.

Lastly, don’t forget to drain your lines and put away the water source connectors before the frst frost. Like any other plumbing, freezing under pressure will cause pipes to burst. I have found draining the lines to be relatively easy. I just take of the end caps and store for the winter.

Figure 4 showing the drip irrigation system's mainline tubing and female hose start
Figure 4 showing the drip irrigation system's mainline tubing and female hose start

A Worthwhile Conifer Garden Project

The cost of the system as pictured in Figure 2, with an average of 3 emitters per plant will be around $200. I would estimate that it would take 8 – 10 hours to install, depending on how handy you are with the hole-punch! This entire procedure may sound time-consuming, and it is! But it is much easier than delivering water by hand over acres every summer.

Once I set mine up, I connected it to the water source with a timer. Now, when I want to water my conifers, I set the timer for an hour or two, go about my business, and return when I can. I can then put the water on another zone, set the timer, and walk away.

I will say that before I turn my back I usually look around to make sure there are no geysers in the watering zone. If I see a large water spout, one of the branch lines has usually become disconnected from the mainline. I usually blame this phenomenon on one of the dogs tripping over it while chasing a ball. Makes more sense than that I might have dislodged it! It’s a simple matter to reattach, but it must be done so that the emitters can do their jobs!

There is a lot more information concerning drip irrigation on the Internet: diagrams, YouTube tutorials, and so forth. In my opinion, it is well worth the time and money invested in drip irrigation to take care of my wonderful conifers!

Photograph by NeONBRAND; illustrations by Jason Smart, Smarty Design Co.

This article was originally published in the Fall 2017 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.