When Wind Meets Water: Irrigation Systems

Although it’s good to have all of the irrigation systems shut down before this dreaded season change, there will be customers who wait until the last minute to call the contractor. If they wait too long, the water in their pipes could expand in volume and cause cracks or breaks in the piping, backflow preventor and sprinkler heads. This can lead to a flood of phone calls in the spring from customers wondering what went wrong and demanding their pipes be fixed.

“Our biggest fear is the water going on the night of freezing temperatures,” said John Sprague, Rain Dance Irrigation, Hamilton, N.J. “We’ll send guys out ahead of time to watch the weather carefully, especially after Halloween when it starts to get cold.”

Wherever there’s a sustained frost or freeze, winterizing irrigation systems is an essential step in their upkeep and maintenance. For contractors, doing it properly and early on in the season can save time and money.

SIGN ME UP. For areas, including those in the southern United States that are high enough in elevation to experience freezing temperatures, where the ground hardens with ice down to a 2- to 3-foot level, irrigation system shutdown is needed, said Sam Moore, Northwest national field service manager, Toro Irrigation, Riverside, Calif.

When to actually start preparing an irrigation system for the cold differs depending on the region. Generally, once autumn hits and the leaves start to fall, it becomes less necessary to utilize the system.

“In New Jersey, we try and have every-thing turned off by Thanksgiving,” Sprague remarked.

Don Turner, edu-cation manager in the marketing department at Hunter Industries, San Mar-cos, Calif., agreed that November is a good time, but the exact date always remains a mystery.

Sometimes, Sprague said his technicians go out by Halloween to shut off the water source and drain the piping above ground.

“If we do some preventative measures then the pipes below ground will take longer to freeze in case of a strong storm early in the season,” Sprague remarked. “We at least make sure the system is off. Anytime it freezes and the system is on the pavement can freeze, causing a safety hazard. On a commercial site, you have to keep things under control – your liability is at stake.”

The technicians at Prescription Landscape, St. Paul, Minn., start winterizing systems Oct. 1, according to Mike Teichert, the owner of the company.

“By Nov. 1, we’re done,” Teichert said. ‘The frost goes down 4 feet in Minnesota so we don’t put in automatic drains like they do in Missouri and Kansas. We really have to make sure we blowout our systems until there is no more water coming out.”

There are many advantages to going out early, but there’s always some small drawback when you’re ahead of the game, commented Rod Waller, technical service manager, Rain Bird Sales Inc. – Turf Products, Tucson, Az.

“It always happens, though – you do winterization at the proper time or in advance only to be surprised by a heat wave,” he said.

EQUIPMENT. It’s a pleasant surprise for a contractor getting ready for winterization to find out the system he or she is working on was designed with winter shutdown in mind, Waller said.

Teichert gives an example: “A polyethylene pipe, I’ve found, is a little more forgiving than a PVC pipe. A PVC pipe is more likely to crack.”

Most contractors charge for an irrigation shutdown service, but it depends on their terms of contract, Turner noted.

“In the northern climates, contractors typically assume the responsibility,” he said.

Based on the system a customer has, there are two different types of winterization procedures: draining the water out using gravity or using the blow-out procedure, which is the most common method and pushes out any standing water using an air compressor.

With gravity, drain valves are installed at the lowest areas of elevation and the water drains into a gravel pit. The system is designed and built for this type of winterization when it is installed.

“People still use this method,” Waller said. “It’s better than nothing and can be very effective when given the correct gradient.”

For the blowout procedure, it’s always good to have a supply of brass galvanized fittings, Teichert said.

“It’s good to have a variety so that you can hook the air compressor hose up to the system because every plumber uses something different,” Teichert added.

Universal remote controls are becoming more widely used by contractors on irrigation systems and they make blowouts a little easier because they give contractors the opportunity to adapt to each irrigation site with a single hand-held remote, said Daydra Presley, general manager of Remote Control Technologies, Redmond, Wash.

“We plug our remote control into an irrigation system controller,” Teichert said. “We walk around with the remote turning the zones on and off and watching the sprinkler heads come up. Because it’s so hard to find enough quality workers, remotes help to cut down the laborers from two to one. Usually you have one person operating the controller and another walking around the site.”

The only problem with the blowout pro-cedure is that some manufacturers do not approve the use of compressed air for winteri-zation and will not warranty damage to their products, Waller said. He also said it’s important to be safe while using the blowout method.

“Proper eye protection must always be worn,” he said. “Extreme care must be taken to avoid excess pressure which can damage valves or sprinkler pipe or cause physical injury due to flying debris. And technicians shouldn’t stand near any irrigation components during air blow-out.”

The most important piece of equipment needed for the blowout procedure is an air compressor. Before understanding what size air compressor is needed based on the work a contractor does, the principles of air need to be reviewed.

UNDERSTANDING AIRFLOW. The problem most contractors have when blowing out an irrigation system is that they are using too small of a compressor, remarked Hank Van Ormer, a consultant with Air Power USA, Pickerington, Ohio.

“The water in the pipe has the resistance to stay in the pipe,” Van Ormer said. “To get out it has to overcome the pressure or head, the gravity of the elevation of the pipe and the friction coming from the sides of the pipe. So, when you’re blowing out the system, you have to fill it fast enough with compressed air and leave the air on long enough to push the water out,” Van Ormer continued, explaining that for a plastic PVC pipe, the pressure and temperature need to be kept low as not to melt the pipe.

The volume or cubic feet per minute (cfm) of the compressor is dictated by the size of the pipe and the pounds of pressure (psi) required to push the air through the pipe, Van Ormer said.

Using 50 to 80 psi is recommended for safety reasons and to save the system from pres-sure damage, Waller warned. He also said the compressor should have a settable regulator.

Most contractors simply rely on experience to teach them how strong the compressor needs to be and how long it should run for each zone, Teichert remarked.

“It all boils down to the size of the pipe,” he said. “Most residential sites have 1-inch piping. If it’s above 1 inch, you really need to know what the mainline pipe size is to give you more of an indicator of what size compressor to use. A 160 cfm compressor will take care of any system up to a 2-inch pipe. When you get over 2 inches, you need to use a 200 or 240 cfm compressor. The cfm will change more from system to system than the psi, which stays consistently around 80 pounds.”

The time it takes the compressor to blowout the air in an irrigation system can also help determine if the right size air compressor is being used. Sprague pays attention to the sprinkler heads during winterization when figuring this out.

“I know I’m using the right size compressor if my sprinkler heads stay up after all the water is blown out,” Sprague noted. “If they fall, that means the compressor is too small and I may not have blown all of the water out of those pipes. It’s all based on trial and error.”

GETTING STARTED. Usually, the backflow preventor, which is commonly above ground, can be taken off of a system and stored inside, Turner said, or it needs to be drained of all water and insulated or wrapped from the cold.

“If it has to stay on, make sure to leave the handles partially open as an escape for excess water,” he added.

The biggest mistake that contractors make when it comes to the backflow preventor is not protecting it before that early storm, said Larry Keesen, owner of Keesen Water Management, Denver, Colo.

“It’s potential for freezing is great,” Keesen said.

The mainline of the system should be shut off before anything else is done, Waller noted.

The compressor hose should then be attached to a mainline connection that will reach all of the system’s zones and is easily accessible, Turner said.

“Sometimes the backflow preventor is the only place the plumber put in for an air compressor connection,” Teichert said. “I don’t like to blowout a system through the backflow preventor because there are some rubber seals that can melt easily from the heat of the air.”

Since compressed air is hot, Keesen said it’s a good idea to have 100 feet of hose between the compressor and the system mainline.

“It acts as a means of cooling the air before it gets into the system,” Keesen advised.

Using the proper size air hose is also important, Sprague said.

“For 25-, 125- and 175-cfm compressors, use a ¾- to 1-inch hose,” Sprague said. “For a 175-cfm compressor, use a 1-inch hose. You lose volume by using too small of a hose.”

Moore added that it’s best to start blowing out the farthest away or highest zones in the system.

“You should start with the highest and have gravity work with you,” he said. “If you start at the bottom, especially at a significant elevation, the water will only drain back down.”

Turning the pressure-regulating valve up slowly to 50 psi, the compressor can be switched on after the zone is opened, Turner said.

“The sprinkler heads should pop up after two minutes,” he said. “If not, turn the pressure up toward 50 to 80 psi.

“When you move on, the next zone should be opened before the first one is closed,” Turner continued. “Also, make sure you turn the compressor on first before opening the valves. It’s a huge volume of air you’re working with.”

Most manufacturers suggest contractors blowout each zone of an irrigation system for two minutes at a time. Van Ormer said it depends on the length and size of pipe and the number of gradients in the system.

However, Waller gives a warning: “Don’t leave the air on longer than it’s needed for each zone. Dry running can cause damage to gear drive rotors that use water for lubrication and cooling. When there is no more mist coming from the head, move on.”

The system should be blown out twice to make sure all the water is removed from the pipes, Teichert said.

“You have to make sure you get all of the water out of the rises and dips in the pipe,” he added. “If you only blow it out once and don’t let it go long enough, the air could just coast over the water in those hard-to-get-at spots.”

Waller has some suggestions: “Don’t ‘cough’ the system clean by building up pressure in a closed mainline, then firing a valve and don’t blow air through the pumps. Blow the system out downstream first, then drain the pump.”

The gradients can be low in some systems, depending on where they’re located, Keesen said, so getting all the water out of a system can be tough.