2018 Guide to Property Irrigation: Everything You Need to Know

The Parke Company is Nashville’s leading landscaping services provider, specializing in tree service, lawn maintenance, hardscape installation, and, of course, irrigation systems.

We have been providing irrigation design, installation, and system servicing to new Nashville construction and century-old landscapes for more than 30 years. We don’t advocate that you attempt to design and install an irrigation system as a DIY project, but we do believe that as the property owner, you should have a working knowledge of how an effective system works.

That’s the objective of this guide. We want you to understand how an effective irrigation system can nourish your investment in landscaping, conserve water, and avoid the very real and costly dangers of an improperly pressurized system. With that in mind, we will walk you through the basics of design, equipment selection, installation, and maintenance of a modern irrigation system.

Hopefully at the end, you will be able to evaluate your existing system or make informed decisions if you are investing in new irrigation.

Irrigation System Design Basics

Measure Your Lawn.

Keep in mind that all the data gathered during this stage is recorded to scale on a software program that will become the “map” of your irrigation system. Because the irrigation system is essentially all about pressure, measuring distances and lawn elevations has to be accurate to avoid dry spots.

Measuring the property can be accomplished with a low-tech tape or a high-tech laser range finder, or even GPS calculations. Property on the lawn (like your house, outbuildings, etc.) need to be measured and plotted as well. This is also a good time to locate and plot trees and existing garden beds.

If your property has a slope, it’s important that changes in elevation are measured and plotted. To determine elevation, all you need are three satellites, a GPS, and a program that calculates all the variables. A DIY method is a bit less sophisticated and involves two stakes, a line of string, a level, and a measuring tape.

Measure Your Water Supply.

This measurement is critical. A mistake here could cause “hammering” in your water line and create a need for expensive plumbing repairs. Ultimately you are looking for pressure (PSI) and volume (GPM) to determine the layout and equipment that will effectively irrigate your lawn. If you are serviced by a water company, they are the most accurate way to determine PSI and GPM.

The process that our expert irrigators use involves checking with the water company for the average static water pressure available to your home, measuring the diameter of the water supply line, and in cases where there is a regulator between the meter and the intake pipe, using a gauge to measure the actual pressure in the home’s plumbing. These measurements are important because we will use them to decide where to tap in for the irrigation system.

Once we determine how much pressure we have to play with (PSI), and the maximum amount of water flow (GPM) available, we can start to lay out the system knowing how much pressure will bleed off during irrigation based on product specifications. This will tell us how to design the system and where to install the sprinklers for optimum coverage.

Select Spray Heads

At The Parke Company we are big advocates of pressure regulating spray heads. The water supply pressure from Nashville, or just about any municipality, can and will fluctuate. When that occurs, it can impact the efficiency of your irrigation system, namely in overwatering or in underwatering.

Pressure-regulating spray heads are products that include a built-in regulator that maintains a more constant pressure for optimal nozzle performance. Typically for spray nozzles, 30 psi provides the best performance. For rotary nozzles, the preferred operating pressure is 40-45 psi. Correct nozzle pressure helps the nozzles distribute the water more evenly and reduces water waste caused by excessive pressure.

Plot the System

Our next step is to plot where the spray nozzles will go and what type of nozzles we will use (cull circle, half circle, quarter circle, or rotary). The placement of these nozzles determines the coverage provided. After that, we need to divide the lawn into zones, designating areas you want to irrigate as a group. The idea is to spread out the watering, preserving the pressure and maximizing the water flow.

Using the product specification sheet, we can determine the water flow rate required for each zone. If a zone exceeds the available flow rate, we can simply break out some of the nozzles and create a new zone.

As you may be suspecting at this point, you most definitely are going to need an automated system with robust control and scheduling capabilities.

Once the nozzles are located, it’s time to plot the pipes and zone valves. When selecting pipe, we always ensure the size of the pipe will be adequate to pull the water flow we need for the “thirstiest” zone. In addition, we plot the location of a backflow preventer, which will eliminate the possibility of contaminating your clean water supply.

Installation Basics

Installation starts by flagging the location of each nozzle. Nozzles are spotted so there is 100% coverage meaning the spray from one nozzle will reach the spray head of the nozzle next to it.

As you might imagine, there is a lot of trenching involved in installation. Because Nashville has relatively mild winters, we only dig down 12” for the main line and 8” for the laterals. We will use a trencher to speed things along but even so, there is a great deal of hand trenching required. So, step one is to dig all of the trenches.

To get a feel for what the piping grid looks like, let’s walk through how the water gets from the supply line to the sprinkler head.

The Pipeline

We will tap into your water supply line at a point between the water meter and the house. Obviously, we need to turn off the water when doing this, but the process takes very little time. Once we install a connection to the water supply line, we install an irrigation system shut-off valve. With this valve closed, we can turn the water back on to the house.

The main line runs from the shut-off valve to the valve box. Inside this box is a manifold consisting of a series of electrically operated valves. One for each zone. So, if your design has three zones, the manifold box will have three valves each connected to an outgoing zone pipe. The valves are connected to a low voltage controller cable that runs back to the timer and programmer. The valves automatically open and close per the schedule entered into the timer.

The zone pipe provides water and pressure for the lateral lines, which feed directly into the sprinkler heads.

Sprinkler Heads

Sprinklers come in a variety of configurations. We have already selected the sprinklers we want and where we want them based on the maximum water flow (GPM) available. The ultimate objective of the sprinklers is 100% coverage and our placement and type strategy assure that goal is met.

There are a variety of connections that can be used to mate the sprinkler with the lateral line. Once that has been done, the sprinkler is stabilized with some dirt in an up and down position with the head even with ground level.

Sprinklers are tough, but if they are sticking up out of the ground somebody is going to run a lawn mower over them or hit them with a weed cutter and do damage.

Controller

The controller is the brain of your irrigation system. It decides when and for how long each zone will be activated. It can communicate with a rain sensor and stop irrigating when nature takes over the job. The better models can also take mandated conservation efforts into account, like watering on odd days only. At The Parke Company we will make a recommendation on controllers but the final decision is yours. We can install and program all major brands.

Controllers can be located inside or outside, although outside requires protective covering and a direct connection with the electrical system. Garages tend to be popular spots for these devices. Interior installations require drilling through a wall to run conduit containing the control cable to the controller, and access to a nearby outlet.

Once the control cable is connected, and the system is programmed, you have a bare bones irrigation system ready for the final phases of installation.

Flush the Lines

With all the cutting, gluing, crimping, digging, and other activity, the pipes are likely to have dirt and debris in them. This material needs to be flushed out so that sprinklers will not be clogged from the inside. To accomplish this, all of the sprinkler heads are removed, and the irrigation system shut-off valve is opened to charge the system with water.

We let this flush run about 15 minutes then close the cutoff valve and replace all of the sprinkler heads.

The final step is backfilling the trenches. Care needs to be taken not to dislodge the sprinkler heads from their up and down position. The dirt is compacted to prevent low spots from forming. Then, using seed or sod, we restore the lawn that was disrupted by the trenching.

What We Didn’t Tell You

There are two components to an irrigation system that we didn’t mention because we didn’t want to confuse you about how the water flows through the pipes. Both components are important. One is required by code and the other is a must have maintenance feature.

A backflow preventer device ensures that water in the irrigation system cannot be sucked or siphoned back into the main supply line of the house. Nashville’s Metro Water Services requires that this valve be placed on the main supply line immediately behind the water meter.

The second item is a drain valve for the irrigation system. Our winters aren’t all that cold but they are cold enough to freeze the water in your irrigation pipes. If that happens you will have a major repair on your hands, not to mention a new pond in your lawn when you first turn the water back on. There are a number of ways to drain your system, but the best way will be determined by the terrain. Once we have inspected the lawn we can plan for effective drainage.

Why You Need The Parke Company to Install Your Irrigation System

We know Nashville and the surrounding communities. We know the soil, the species that thrive (and fail), and we have been at this work in Nashville for more than 30 years. The people in Nashville are very pleasant but they are also practical. They won’t let you stay in business for three decades unless you have a stellar reputation for delivering as promised.

We have the experience, staff, and resources to design, install, and maintain irrigation systems of any size anywhere in the Nashville area. Call us today and experience The Parke Company difference for yourself.

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