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Drip Irrigation - Laying It On The Line!

By LariAnn Garner (LariAnnJanuary 30, 2009
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Here is where the pipe hits the ground, as it were! You know where your water is coming from, you've planned for filtration and valving, and you have an idea about what kind and how many of the drip emitters you want in each zone. Let's piece it all together and see what we've got . . .

Gardening picture

Drippers on the Main Line . . .

Now that you've reviewed your proposed installation and know how many zones you want, consider this: if you plan on using the "shrubblers", I suggest you have no more than 40 of them in a zone. More than that and you have to open them fully up just to get a dribble, you then risk the loss of the little caps as they will be almost fully unscrewed, and the emitters then become more susceptible to clogging due to gradual deposition of solids from evaporating water.

Your first task is to figure out how much of the 1/2 inch black poly pipe you will need. This pipe is what will serve as the mainline for each of your zones. Starting at your zone valve, and using a tape measure or pre-measured piece of string, lay out where your pipe will be running to complete the zone. Write down your measurement, then move to the next zone. For example purposes, let's assume we will have just one zone and that the mainline pipe will run for about 50 feet.

Spaghetti for your plants?

Next, you need the 1/4 inch tubing that will connect the drip emitter to the mainline pipe. This "spaghetti" tubing will enable you to place the drip emitter stakes right in the pots to water each plant on the zone. This smaller tubing comes in two types - poly (polyethylene) and vinyl. The poly is somewhat cheaper but the vinyl is thicker and more flexible to work with. If you have a lot of emitters to install, you will appreciate the flexibility of the vinyl, especially after you've installed more than 25 of the emitters! The vinyl tubing also comes in two colors - black and brown. Your choice depends upon whether you want the tubing to be less conspicuous; the plant won't care at all. You'll need a good sharp pair of pruning shears to cut both the mainline pipe and the smaller tubing with. For example purposes, let's assume you have 25 potted plants that will be on this zone, so that means you need 25 drip emitters and 25 cut lengths of the 1/4 inch tubing. If most of your plants are in the same size pots, and they are all about the same distance from where the mainline pipe runs, you can measure how much of the 1/4 inch tubing you need for one plant, then multiply that by 25 to figure how much of the tubing you'll need. If each of your emitters is going to be about 3 feet away from your mainline, then you are going to need 75 feet of the 1/4 inch tubing for your zone.

Finally, you need 25 of the emitters; the shrubblers come complete with a barb connector attached to the stake. This little connector is what you will remove and use to connect to your mainline. When I did my zones, I inserted the connector into one end of my length of 1/4 inch tubing and the shrubbler stake into the other end after first blowing through the length of tubing just to be sure nothing was stuck in there. To attach to the mainline, you'll need one of the handy little poly pipe hole punches that are available in the same shelf area as all your other drip irrigation supplies were. Just be sure you don't punch through both sides of the mainline or you'll have a goof hole to plug!

Straight around?

In my example here, I'm thinking about a straight-line run of mainline, which assumes that your plants are spaced more or less in a linear group. Of course, this may not be the case at all, as your plants can be around the patio in a sort of crude circular arrangement, or they may be arranged in two groups, one on each side of where your valve will be. You can loop your mainline pipe back to a common tee connector in the first case, making a closed circle, or use a tee connector in the last case to give your zone two "arms", as in the arms of a tee. Many configurations are possible, but the most common in my experience are the one-way linear or curvy zone and the "out and back" or closed loop zone. In any event, I recommend that each of the zones in a multiple-zone installation be set up according to the most efficient arrangement of plants. If this drip system is to be used mainly when you are away, the arrangement of the plants can be less aesthetic than if the system is going to be used whether or not you are away.

Once you have your emitters, length of mainline, lengths of 1/4 inch tubing, and your filter and valve location, it's time to put it all together with pipe fittings. In our simple example, you'll need a fitting to connect to the outlet of your valve, and you need a drain fitting to install at the end of your zone (if your zone is not a loop). For a looped zone, you need the valve outlet fitting and a tee connector to form the loop. Because so many design layouts are possible, I cannot cover every type of fitting you might need. You should know that you have two basic fitting designs to choose from: the insert fitting and the compression fitting.

Fit As . . . a fiddle?

Each of these types has particular pros and cons, but both of them are a bit of a pain to remove, once installed. So I suggest that you be about 100% sure of your layout configuration before installing any actual fittings. The insert fittings are usually gray in color and, as their name suggests, insert into the open end of a piece of mainline pipe. They are then secured in place with a pipe clamp or crimped ring. These you should slide onto the pipe before inserting the fitting. The compression fittings require no clamp or ring because they go on the outside of the mainline pipe (i.e. the pipe itself inserts into the fitting). Mainline pipe comes in several sizes; 0.700 and 0.710 being two of the most common. The measurements are the outside diameters of the pipe. The difference doesn't seem like much, but the compression fittings for a smaller size should not be used for a larger size. The larger size is shown in the thumbnail picture above as the Toro "blue stripe" pipe roll. The smaller diameter pipe is usually all black. The compression fittings for the smaller diameter are all black as well, while those designed for the larger diameter have blue rings at the openings. Your hands will get a little workout from inserting the pipe into the compression fittings as they are a very snug fit. Getting the pipe back out in case of a mistake is even harder because the inner part of the fitting opening sort of bites into the pipe when you try to pull it out, which is why I cautioned about installing fittings until you are sure of your layout.

I've seen some versatile fittings that are almost like a cross between the insert and compression types, and which can be used for all different sizes of 1/2" poly pipe. If you can find these, and are willing to spend a little extra for them, they will make your installation go easier.

Always get the "lay of the land" first!

Before you start anything, I suggest you go to your local Home Depot or other big box hardware outlet and browse their drip irrigation section. You'll see examples of all the things I've described, plus a lot of other parts that are used in specific or unique situations you may or may not encounter in your installation. Home Depot carries a lot of the DIG brand of drip irrigation supplies; the electric solenoid valve I used is a DIG brand valve, Model 7001. You can get really great prices at Irrigation Direct if you don't mind ordering via mail order. I got a lot of my supplies from them as well, and their electric ball valve, the Model DD-HEDT, is the other valve I used in my system. Also be sure to take advantage of the do-it-yourself information available on both the DIG and the Irrigation Direct websites to help round out your drip irrigation education.

Image credit: Toro and LariAnn Garner


  About LariAnn Garner  
LariAnn GarnerLariAnn has been gardening and working with plants since her teenage years growing up in Maryland. Her intense interest in plants led her to college at the University of Florida, where she obtained her Bachelor's degree in Botany and Master of Agriculture in Plant Physiology. In the late 1970s she began hybridizing Alocasias, and that work has expanded to Philodendrons, Anthuriums, and Caladiums as well. She lives in south Florida with her partner and son and is research director at Aroidia Research, her privately funded organization devoted to the study and breeding of new, hardier, and more interesting aroid plants.

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Discussion about this article:
SubjectTopic StarterRepliesViewsLast Post
In line emitters Catma33 2 33 Jun 18, 2010 8:44 AM
great phicks 1 17 Feb 2, 2009 2:52 PM
Drip Irrigation - Laying It On The Line! fc_upland 0 14 Feb 2, 2009 1:20 PM
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