by John Swaringen
We’ve heard it all before, haven’t we? Drip lines clog and stop working. They take too much time and labor to install. It’s harder to complete bed maintenance around drip irrigation. Overhead watering is easier and is just as good for the plants.
Irrigation contractors and landscapers can come up with lots of reasons not to install drip irrigation. In reality, however, for trees, shrubs, and all other plants in beds, low-volume drip irrigation is hands-down the best way to provide water to them. And in my opinion, it is really the only way.
In the remainder of this article, I’ll explain why I make that statement. I’ll also give you a better understanding of how to install, maintain, and convert existing zones to drip irrigation. I hope to better equip you with questions you should ask and the confidence you need in order to work with an irrigation contractor on your properties, and to offer my thoughts on how to better sell the irrigation portion of your landscape package, along with the irrigation contractor, to your customer.
Let’s first take a step back to look at landscape irrigation as a whole. On most properties, an irrigation system will water turf, trees, shrubs, and beds. In addition to the plant material being irrigated, consider the areas of sun and shade, the slopes involved, the soil types, and the soil compaction in selecting the water delivery method as well as the run times and schedule for each zone. Since turf zones are designed to completely cover as large an area of grass as possible, they should always be on a separate zone from planted beds. It is easier and more economical of course to have the turf heads overthrow into the beds, but getting enough water in the beds, especially to establish new plantings, is hard to achieve without over watering the turf. And in beds, you normally don’t need all the area covered equally, instead you prefer the water to be delivered directly to the root zone of each plant in an amount in line with each species’ needs. Dedicated bed zones with drip irrigation offer the best delivery of the water to each plant.
Installing bed zones with heads that provide overhead water to the plants is also an option, and one you may see often on landscapes you inherit. Compared to drip, overhead watering is really no better than having a lawn zone throw into a bed. You still have the potential problems for diseases due to the consistently soaked foliage, especially with new plants that may already be suffering some degree of transplant stress while getting established in their new environment. Overhead watering spreads all the water evenly in the bed also, which means some species of plants will be over-watered and some not watered enough. As plants grow and mature, you then get knockdown of water at some point, which causes limited or no water in some spots and puddles in others. It’s also hard to avoid splash-back or overthrow onto the house, and we know what that can do to the woodwork over time. So again, water from properly placed drip lines directly into the ground at the root zone is the best option for plant health and vigor.
Advantages of Drip
The two most significant benefits from drip irrigation are the ability to water each plant per species needs and to get the water into the ground directly at the root zone. As a landscape contractor, you understand the importance of properly selecting plants per site conditions, using good planting practices (probably with necessary soil amendments), and then providing the appropriate amount of water for plant establishment and continued vigor. You know the problems associated with not enough water, and know bigger problems can develop from over watering. With drip, you control how much water each plant gets by adjusting the amount of drip pipe you put around or near each plant.
Since most beds probably have multiple species with different needs, this is an especially valuable characteristic of drip irrigation. For example, you could loop a hydrangea with high needs three times, an ilex species only once, and simply run a line by perennials that are more delicate, all in the same bed. And if part of a bed has a different sun and shade exposure or different slope, you adjust the amount and location of pipe accordingly. Your irrigation contractor may not know each plant’s requirements, but by consulting with the contractor I’ll bet you can get it close. If you miss by a bit, it is easy and quick to add more pipe or remove some to adjust the amount of water. And with experience, like everything else, it will get easier.
Once you have plants selected and planted, you know the importance of strong root development in getting plants established quickly on a new site and assuring their long-term health and vigor. Roots that grow deep and dense are essential so they won’t dry out as quickly during times of drought and high surface heat. And what better way is there to encourage roots to follow the water down than with drip irrigation from a slow-soak cycle that delivers the water just below the surface? In most cases, you can’t get enough water into the ground from overhead, especially through a layer of mulch, without having runoff and possibly erosion problems.
Before we move on from the ‘why drip’ topic, here are a couple more thoughts. We all know that deep watering, less often, for longer periods is best, if the soil will hold the water, and that we should set our watering schedules accordingly. However, in intense afternoon heat conditions, new plantings and high-water-need plants can sometimes suffer, and need an afternoon ‘freshen-up’ cycle. Wetting the foliage at these times can cause more problems, but with drip at the root zone, there is no problem. Municipalities impose landscape water restrictions some seasons during drought times, but they will sometimes allow usage of drip zones without restrictions. When planting in environmentally sensitive areas, conservation commissions will allow drip irrigation in some cases, but no overhead watering that has a greater chance of producing runoff. In these cases, drip irrigation over the root zones of the desired plants is the most effective use of water on a landscape since it gets right into the ground to the roots.
Here is one last benefit of using drip zones in foundation beds. Has watering window boxes or pots on steps or porches been a hassle? With punch-in connecters on a drip line, micro-tubing, and micro-emitters that have adjustable flow controls, you can water them through the automatic system and not be tied to a hand-watering schedule any longer.
Even though some irrigation contractors know drip irrigation is best for a landscape application, they are sometimes reluctant to recommend that option. They feel it is too labor-intensive to install, is too hard to maintain, may be too costly for the property owner, and may fail over time. My goal is to arm you with enough knowledge and understanding of why drip irrigation is best in order to help you locate a contractor who will help you design the systems you need and with whom you can build a lasting and profitable relationship.
Drip irrigation that is installed properly is as dependable as any other form of landscape water delivery. You’ll want to make sure that a drip filter/pressure reducer assembly is installed after the zone valve on each zone; alternatively one assembly can be installed on the mainline before a set of valves if they are all serving drip zones. The filter keeps clean water flowing to the drip emitters, and the pressure reducer is essential to keep a constant lower pressure in the lines that prevents the ‘suck back’ of debris into the emitters when a zone valve closes and the flow stops. It is also necessary to run a zone line (usually one-inch pipe) to each end of the zone to feed the drip lines, otherwise the line may not carry enough water through the smaller drip pipe to keep a consistent flow at the farther points from the valve. Installing multiple feeds off the zone line and connecting all the drip pipe in a loop will keep the flow and pressure constant throughout the zone.
As mentioned earlier, installing the drip lines in the beds will vary according to the plant species. The spacing of the emitters on drip pipe can vary as can the flow from each emitter, so you need to know the specifications of your product. Over a normal run cycle of say 45-60 minutes, depending on the flow rate and soil type, each emitter is designed to disperse water away from the pipe at the same distance as the spacing of the emitters on the pipe. Then, using the water requirement for each plant as your guide, you can lay the pipe in a grid running by or between plants, run multiple lines by rows of plants, loop the entire root zones of larger shrubs and trees, or create any other configuration that provides the desired water distribution. Remember, if a bed is on a slope, water will run downhill; it’s important to position pipes with that in mind. Again, with experience, a contractor can quickly learn to be efficient.
The timing of the installation of drip lines can also make the job easier, and it only requires coordination between contractors. After the plants are installed in the beds and before the mulch or other top-dressing is applied is the best time to install drip lines since the plant species are evident and the locations of the lines are easily determined. If the lines also need to be scratched in below the surface, it is easier if you don’t have to move the mulch and spread it again.
The amount of drip pipe you can put on a zone can be determined in the same manner as the number of heads on a zone. By knowing the flow at a working pressure for each head and nozzle that is installed, you can use simple math to determine the flow per minute of the drip pipe you are installing. For example, the standard pipe I use has an emitter every 12 inches and a flow rate of .9 gallons/hour per emitter. If I lay 100 feet of pipe it will use 90 gallons/hour. Dividing by 60 minutes allows for 1.5 gallons/minute for every 100 feet of drip pipe. Then dividing the flow available from the water source by 1.5 gives me the approximate number of linear feet of drip pipe (in 100 feet increments) that can go on a zone.
You may find that you need to convert an existing overhead watering zone to drip. This upgrade is a relatively simple task. Locate the valve for that zone, and add the filter/pressure reducer assembly on the zone line. The feed line is already in place, so simply remove the existing heads, make those fittings the feeds to the drip line, and lay the drip pipe as if it were a new zone.
Maintaining drip irrigation may appear to be challenging, but becomes easier after working with it on a few properties. Checking the removable drip filter and cleaning it as needed is necessary for full flow and operation. Drip lines may work themselves to the surface, but can easily be buried and stapled down again. Lines can get cut during bed maintenance work, but they are easily repairable in many cases by the landscapers themselves. All you need are the fittings and a little pipe at times. If you add, move, or remove plants within drip irrigation zones, you simply add, move, or remove the associated drip lines to keep watering as needed. Remember drip is a low-volume delivery system, so you will need to monitor the soil moisture levels and adjust the run times as needed.
I hope this gives you a better understanding of ‘why’ drip irrigation and ‘how’ to work with it so that you will be better able to find and work with an irrigation contractor. The landscapes you install are investments for the property owner, sometimes significant investments. Proper watering is a big part of protecting that investment for them, and should be sold that way. Drip irrigation may be a little more costly, but the benefit of getting the landscape established and flourishing as quickly as possible adds value to your services. Replacing plants that fail or converting to drip irrigation after beds are established can be more costly to the homeowner in the long run. So I encourage you to commit to drip, price it accordingly, and sell the value that drip irrigation provides.
I can’t end without mentioning water conservation in landscape irrigation. Water is a finite resource on earth and should be conserved at all times. Analysts say that at least 30% of all irrigation water is wasted; some even say the number is closer to 50%. A good number of water conservationists, some with loud voices, are pushing to set limits on household water usage, which would stop all irrigation. Think of what that would do to our businesses and the landscapes we care about.
So please be aware of waste on all properties you touch. Make sure heads aren’t throwing excessively onto streets and driveways. Make sure irrigation water isn’t running off or leaching past the root zones of plants. Be sure leaks are fixed when they are found. And make sure the water is getting used by the plants as intended. Drip irrigation is the most uniform and efficient delivery method in the industry – it gets water directly to the roots, is not affected by wind, and hardly any evaporates away. That’s just another reason to use it every time you can.
About the Author
John Swaringen is a Certified Irrigation Contractor and Plant Health Care Specialist for Bartlett Tree Experts in Osterville, MA. He can be reached at firstname.lastname@example.org.