Sunday, August 9, 2009

Irrigation Heads: A Portrait in Parts

The irrigation system has now automatically turned itself on and off three times since we got the east and south sides of the house hooked up. Seems to be working very well. There is still a lot of crispiness, but I think it's a relic of the pre-irrigation days. Within a few weeks we should know for sure whether or not the system is doing all that we want.

Meanwhile, I thought I'd summarize what I've learned about the common types of irrigation heads you find at LoweDepot.

Mainly, what I've learned is that I'm not nuts about any of the options, but let's look at them one by one.

Spray Heads / Shrub Spray
These release a fine, light mist in fixed patterns. Adjustable-pattern heads allow you to set the pattern from something like a 10-degree to a 360-degree radius. Most commonly used in beds. Some, like the one below, emit two tiers of spray--a top tier to reach farther and a bottom tier to cover the area very near the head.

These sprinklers are driven by water pressure and are not hooked up to electricity.

I dislike the fine mist, because I don't think it penetrates heavily mulched or weed-barriered beds very well. I aslo dislike the fact that the fine spray is so easily blown off-course by the wind.

180-degree spray head pop-up sprinkler in the shade bed

Spray heads can also come in other spray patterns, like skinny triangles, squares, or--as in the example below--skinny rectangular strips. We have two of these, and I think they are the least effective heads in our whole yard.

Rectangular spray head by the gazebo

It is possible that if we had installed two skinny rectangles with the heads at opposite ends facing each other, that the double coverage might have been more effective. Spray patterns are indicated on the head labels using simple geometric icons like the ones below. #1 is what we currently have--one on either side of the gazebo. The red dots indicate where the head is relative to the spray.

If we had #2 + #3 facing each other on either end of both sides of the gazebo (total of 4 heads instead of 2), we might have had better success.

Rectangular spray patterns

Rotary Head
My preferred forms of spray head is this, the gear-drive rotor or rotary head. It puts out bigger, heavier droplets, which presumably do a better job of penetrating the mulch. These also come in adjustable patterns, which is the only kind I am inclined to buy at this point. Our approach is so experimental that the flexibility they provide is really handy.

They only come in variants of circles (half-circles, quarter-circles, etc.).

The down side is that the shortest of these that I know of is a 15' Orbit model. In a shrub bed, 15' is often a bit much. They are most frequently used for watering lawns.

Small rotary head by the study door

With all kinds of irrigation heads, you are supposed to strive for "head-to-head coverage" (which we unfortunately did not know when we installed the shade bed irrigation). This means that you want the outermost spray of one sprinkler to just reach the next head, and you want the outermost spray of that head to just reach your first head. While this seems like propaganda to sell more sprinkler heads, experience suggests that it is also good advice to achieving full coverage. Without head-to-head coverage, you tend to get scanty irrigation under the arch of your spray.

With rotary heads, using a head-to-head arrangement is more than usually important because they shoot a forceful stream that aims a minimum of 15' away. If you don't have overlapping spray, you'll get doughnuts of relative dryness.
Lowes' illustration of head-to-head coverage.

There are two kinds of bubblers: mushroom bubblers and flower bubblers (sometimes called "flower-head bubblers"). These refer to the shape of the spray, not to the plants for which they are appropriate.

We only knew of mushroom bubblers, and installed them in our Mutabilis rose Zone. They don't really spray, so much as seep gently. The head is basically designed to improve over a simple garden hose by slowing the flow so that it sinks in rather than runs off. The one below is fully open and on (they are usually adjustable flow.)

Bubbler in the mutabilis bed

In retrospect, I wish we'd chosen flower-head bubblers instead, as they pop up a little and emit several streams of water from multiple holes around the top of the head in a narrow (~2') radius.

Both are designed to soak deeply, which is great for small trees and shrubs, but I suspect the flower-heads achieve a slightly wider radius.

Spaghetti Tubing
Spaghetti tubing is like bubblers in that it is designed to soak, not spray. People frequently put emitters on the ends of spaghetti tubes to slow the flow down and simultaneously increase pressure in the irrigation system. For our roses, we generally prefer to just use the tubes as is in order to deliver more water.

Bubblers and spaghetti tubing are the most efficient forms of irrigation because they deliver water directly to the roots in large enough quantities to penetrate mulch and weed barrier, and with little to no interference from the wind.

The drawback to the spaghetti is that it is extremely specifc--it disburses water in a pretty tiny radius (~6-12"). Spaghetti best serves a bed with a relatively fixed population, mostly of shrubs. If you change out seasonal annuals or herbs, you'll constantly be adding new tubes and tying off old tubes, and as the tubes sometimes wander, some of your seasonal color will probably end up underwatered.

A headless spaghetti tube in the rose garden

Open 3/4" Tubes
This is not a particularly good solution--we will probably be changing them out for bubblers. Three of our trees just have open 3/4" tubes. Our arborist told us to mollycoddle our young trees by turning the hose on more or less full pressure within the little levees for about a minute every other day. That should be enough to fill up the levees, which should provide a young tree with the water it needs. This open tube approach was an attempt to automate that task. Now that the trees are older, they could probably use a slower, deeper soak.

3/4" Tube on a Quercus polymorpha

Finally, here's the irrigation computer we're using.

12-station irrigation computer

We got the "12-Station Super Dial - Outdoor" irrigation computer. It wasn't till I visited the Orbit website a couple of minutes ago that I discovered they have a range of products beyond the few available at LoweDepot. I've been so programmed by the LD folks that I often forget there are other home improvement store options. For example, I'm not nuts about any of the tubs on display at LD, and I periodically slip into tub-related despair because I forget that there are other stores that sell tubs. There is, in fact, a whole internet full of tubs. All of which is to say that although this unit is okay-ish to use, I rather wish I had surfed a bit and at least considered buying online.

I mean, look at this beautiful thing:
Fancy irrigation computer

It has a remote control! I'm sitting in the living room; it starts to rain; I just reach for my trusty Orbit irrigation control station remote control and BAM! irrigation cycle deferred! Plus, it displays in blue. Ah, well. Some other lifetime, perhaps.

The system's not perfect, but
I feel pretty good about the fact that our plants are getting at least some water on a regular basis during the drought. The system, which is easily extendable, also means that any new plants we buy have a better chance than, for example, our poor, benighted baldcypress ever did. And hopefully we'll get some fast-moving shade that will help shield the house and bring down our power bills. Shade and water: two things I love.

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