A “new” irrigation option for larger installations

Photos by Kristi Bishop.

Only two wires, a hot and a common, run to each valve, and a decoder is used to signalthe controller.

Dan Bishop can’t figure out why two-wire irrigation connection systems aren’t more popular on the West Coast. It has increased his company’s potential, as well as profitability, however many companies haven’t even heard of it—and many clients won’t consider it.

Bishop admits it took him a few years to try the two-wire system, which is popular in irrigation hookups on the East Coast and, especially, Florida. He first heard about it years ago, but it took a lot of convincing for D & K Landscape ( in Las Vegas, where Bishop is chief operating officer, to try it.

“I would say that two-wire would be the biggest innovation in those years,” Bishop says, referring to the almost 13 years that the company has been in operation.

Two-wire irrigation is a simple method of hooking up irrigation valves to a controller, using only two wires along the string of valves. Instead of a different wire running from each valve all the way back to the controller, plus a common wire, the valves are connected in series like Christmas tree lights. There’s a hot wire and a common wire with a decoder wired in at each valve, allowing a special controller to turn the valve on or off. On a large job, instead of bundles of 40 or 50 wires of all colors running to the controller from several directions, there are only two wires the length of the run.

In 2007, D & K undertook a massive commercial irrigation and landscape job at Arroyo Market Square in Las Vegas, which was to become the largest retail center in southern Nevada, with several large retailers located on 107 acres. When D & K got the job, its irrigation supplier, Horizon, recommended using a two-wire controller on the project.

This was the first time the company had used two-wire, however Bishop says it meant huge savings in several areas.

“We have one controller running about 155 valves,” Bishop says. This is an all-drip irrigation system, watering many small islands of xeriscape vegetation among vast parking lots and streetscapes. It featured a varied plant palette, including large plants such as palm trees.

D & K used a Tucor ( TWC-NV 200 controller made specifically for two-wire projects of up to 200 valves.

Bishop says that on a normal commercial landscape job of this size, the controller would be one of the last things to go in because of the complexity of the wiring and the lack of electricity for landscaping on a new construction site. As plants are installed, they would be watered by hand or by a temporary set of controllers hooked into power as it became available. Some plants die on those jobs and have to be replaced during the many months of construction. The two-wire controller was set up in a temporary location in the construction trailer right at the beginning, and as valves were added they were tied onto the end of the last valve. Valves were added along the way by splicing into the two wires, and drip lines could be tested as they were installed. Because the controller can be placed anywhere on the two-wire string, at the completion of the Arroyo Market Place job it was moved across the site and tied into the two wires at the opposite end.

The 107-acre Arroyo Market Square project was overseen by Dan Bishop, whose company savedthousands of dollars by using two-wire irrigation connections on 155 valves.

Almost no plants were lost on this project, and there was no extra labor required to water them by hand or on weekends. There were big savings on the amount of wire needed. At a time when copper wire was expensive, he estimated the project would require about 350,000 feet, or 40 rolls, of wire under the multiple-wire system. Because only two wires were needed, it required only 17,000 feet of wire, or less than four rolls.

Although the two-wire system calls for a heavy 16/2 wire (American Wire Gauge, 16-gauge, two conductors), Bishop calculates he saved about $45,000 in wire costs alone. He used a Rain Bird Maxicom wire.

An extra cost in the two-wire system is the decoders required. One is usually needed for every valve, but the TWC-NV 200 allows the use of two valves per decoder. In addition, surge protectors and lightning rods are recommended every 500 to 600 feet along the line.

This Tucor two-wire controller boxlooks much the same as any other,except that it isn’t cluttered with dozensof valve wires.

“The difference in expense between the two systems is not just the cost of the extra wire, but also the cost of labor to install the wire,” Bishop points out. The ease of installing only two wires in series along the entire run is significant, and workers don’t have to keep track of the colors of wires at the controller. The valve decoders are programmed into the TWC-NV 200 as they are added, and irrigation can begin immediately. He estimates that about one-tenth of the labor is required for installation. “That’s a lot of hours saved.”

He adds that another valve or set of valves can be added by simply splicing into the two wires. It can be added at the end valve if another phase of development begins, or it can be added laterally if a flowerbed or turf is installed after the project is completed. With the old system, the entire wire conduit would have to be dug up so that another wire could be sent from the valve to the controller.

“We still have the capability to run another 50 valves or so on this system, and that wouldn’t be possible on the old system,” Bishop says. Another benefit of the system is the ease of repairing a break in the wire. If a wire is cut, it can be located by tracing the next inactive decoder, and then repaired with two waterproof splices. On the multiple-wire system, the entire bundle of wires would have to be sorted out by color and spliced. And, the conduit is less expensive. D & K would normally use 4-inch Schedule 40 PVC to protect the wires on a job of this size, but with only two wires, he used 2-inch PVC.

Bishop says that due to the economy of scale and wire savings, he thinks that only large jobs are feasible for two-wire systems. He recently used a smaller Tucor controller for a job with under 100 valves, but the savings were less as less wire is used. He adds that it is difficult to convince clients to use a two-wire system because they are so rare out West. In addition, landscape architects are usually unaware of the availability and reliability of two-wire systems, and they continue to specify traditional controllers in their plans.

It is a “mystery” to Bishop why this system is foreign to the landscape industry west of the Mississippi. Many manufacturers offer two-wire controllers, however, few distributors sell them in western states; most are only for jobs such as large commercial projects or highway landscape irrigation where long runs are necessary.

“We have a fully automatic irrigation system on every project we do,” Bishop says, and he would like to use two-wire on more of them. The Arroyo Market Square project, for which D & K won a design award from the Nevada Chapter of the American Society of Landscape Architects, proved to him that the system is both efficient and dependable.

Don Dale resides in Altadena, Calif., and is a frequent contributor to Turf. He has covered the green industry for more than 10 years.