Valves & Solenoids
The average person doesn’t spend a lot of time thinking about valves, or the solenoids that make them work. If you’re an irrigation professional, you might spend a little more time thinking about them. Still, you might feel that the most exciting thing about valves are the spiders or snakes that you might find nesting inside their boxes.
Yet, our very lives depend upon valves. The pump for the human body’s circulatory system, the heart, depends on its valves to work properly. When one of them springs a leak, or doesn’t open and close correctly, we’re in big trouble.
Very simply, a valve is a device that assures that fluid flows in just one direction. In an irrigation system, it’s the component that, once signaled by the controller, allows water to flow out to the sprinklers, rotors or drip emitters in a zone, and shuts it off when the allotted watering time is over. It is, essentially, a water gate.
Valves can have a number of different configurations. The flow control, (the stem and handle) is optional on most one-inch valves, but is standard on larger sizes. The manual operator is standard on most valves, but not all. The bonnet can be attached to the valve body with screws, bolts, or a threaded connection called a ‘jar top’ that doesn’t need tools to remove. Many one-inch valves can be ordered with different inlet/outlet connections, such as female or male threads, solvent welded and barbed, for poly pipe connections.
There are three types of valves used in landscape irrigation. Their names are determined by the location of the inlet/outlet: globe, angle or globe/angle. “Globe valves are most commonly used on residential landscape irrigation projects and some small commercial projects,” said Jeremy Hunt, owner and president of Hunt Irrigation, Inc., in Lincoln, Nebraska. “Globe/angle or angle valves are more common on commercial systems.”
“The difference between the three is how the water enters into the valve,” he explains. In a globe valve, the mainline pipe is connected to the inlet of the valve on one end, and the lateral pipe is connected to the outlet straight through on the other side of the valve. In an angle valve, the inlet is on the bottom of the valve body, and the outlet is at a right angle on the end.
The globe/angle valve has two different inlets. The pipe-attach on the end inlet and the bottom inlet has a threaded plug. If the bottom inlet is used, the threaded plug is moved to the end inlet.
Choosing a valve
When asked what a contractor needs to know when choosing valves, Ron Wolfarth, a contractor division product manager at Rain Bird in Azusa, California, said, “Everything about the particular site or application.”
That includes: whether it’s a residential or commercial system; the maximum water pressure; any pressure fluctuations; the minimum and maximum flow rates; the water quality; the frequency of use, and the need or desire for flow control.
In residential settings, Hunt always uses a globe valve, and in commercial, it’s always angle valves.
Since there’s less pressure loss through an angle valve, that makes it a better choice—in his opinion— for a commercial application, where there are many more irrigation heads, and pressure is more of an issue.
“Typically, on a commercial site, we’re installing a main line 18 or 24 inches deep. To bring that valve up to a serviceable height—you don’t want a valve two feet down in the ground—by coming in at an angle, we can come straight into the bottom of the valve, and we get a little better finished product.”
Residential valves are typically smaller, because the pipes are. “The valves for that application are the three-quarter inch, the one-inch, and sometimes, the one-and-a-half inch,” said Jorge Rivera, a product marketing manager at Irritrol in Riverside, California (a division of Toro).
“Usually, the one-and-a-half inch size is used in commercial applications, along with the two-inch and three-inch. The three-inch valve is found on really big projects, where tons of water is flowing, up to 300 gallons per minute (gpm).”
Commercial flow rates are greater, 50 to 120 gpm, and the water pressure is higher. Residential valves typically have 100 to 150 psi pressure ratings, and commercial, up to 200 psi.
“In a residential setting, you’re limited to the capacity of the water meter at the house, usually ten to 15 gpm,” said Wolfarth. “A one-inch valve is usually the biggest that it makes sense to use.”
Some valves, manufactured for use with reclaimed or recycled water, have diaphragms made from EPDM (ethylene propylene diene monomers). EPDM diaphragms stand up better to the high levels of chlorine found in treated water.
Depending on the budget he’s working with, Steve Hall, CIC, CLIA, FWSAP, vice president and co-owner of Stahlman-England Irrigation, Inc., Naples, Florida, will try to specify ‘dirty water’ EPDM valves for such applications. They cost $25 to $50 more than regular valves, however, which really adds up in a commercial application where you might have 100 zones.
Water from a city main usually won’t contain scum or algae, but reclaimed, pond and lake water often does. If that’s the water source, there’s another type of valve that should be considered, called a ‘scrubber’ valve. It’s a self-cleaning model with mechanisms inside that continuously clean the internal filter. Hall has used scrubber valves on many occasions.
There is one more type of valve we need to talk about, and that is the anti-siphon valve. “They’re common in California, but they’re also used in a lot of other regions,” said Rivera. It’s an angle valve with an atmospheric vacuum breaker (built into the outlet side of the valve) attached, and sold as a single unit.
On the side of the valve is a round structure with a rubber float inside of it. When the water pressure comes on, the float rises, and it gets pressed against a seat, which seals the exit to atmosphere for the water, and then the water is directed down into the pipe.
If there’s a backflow condition, where water is moving backwards through the valve, the water level would drop, the float would come off the seat, and air would be introduced into the valve, breaking the siphoning effect.
The case of brass vs. plastic
Modern landscape irrigation valves are made of fiberglass- or nylon-reinforced plastic, and sometimes, brass. The vast majority are plastic. While some contractors may prefer brass valves for their longevity (a brass valve can last 50 years) they are more expensive.
“Plastic valves were introduced to the market more than 50 years ago,” said Wolfarth. “Prior to that, if you wanted an irrigation valve, it was brass. That was the industry standard, and the only thing available.”
“Sometime in the late ‘60s, early ‘70s, a plastic valve was introduced. But, as is the case with a lot of technology, this early version wasn’t very reliable or durable, and caused some horrible failures.” Things like, houses that slid down water-eroded slopes.
Incidents like these caused some contractors to swear they’d never use another plastic valve as long as they walked the Earth. But the plastic valves we have today are of much higher quality.
Irrigation brass is actually bronze, which used lead in the smelting process to fill in microscopic imperfections. Older brass valves that are still in the ground are likely to contain lead. Modern brass valves are lead-free, but making them that way adds to their production costs.
Brass valves continue to be made, because there are still some good reasons for using them. Many municipal park irrigation systems were built with them, and the irrigation managers may want to carry just one set of replacement parts. “I can see using a brass valve where the soil or water is very corrosive, or in an extremely cold environment, where the valve box is exposed,” said Hall.
When valves fail
Hall says most valve failure can be attributed to the same thing that causes human knee joints to fail. “Plain old wear and tear,” he says, i.e., age. In Florida, where he works, some of them age prematurely. The reason: it’s common there to irrigate with water from sandy wells. The abrasive silt slowly sandpapers all a valve’s parts, especially the diaphragm.
Some other frequent causes of failure include poor installation; debris blocking the solenoid ports; not flushing debris out of the main before installation, and burnt solenoids.
Others include the use of ‘pipe dope,’ obstructing solenoid ports with PVC solvent or copious amounts of PTFE (Teflon) tape. Another is poor or broken wiring from the controller to the valve, bad splices, or not using waterproof connectors on splices. This causes shorting out, or insufficient contact.
Hunt says that if a valve malfunctions within the first three to five years of installation, it’s probably the result of something that happened during the installation. It could be a bit of debris left inside a mainline that eventually causes the valve to stick in an open position.
He added that the way a system is designed also affects the longevity of a valve, especially the diaphragm. If a system is forced to carry a flow beyond what’s considered a safe capacity, a diaphragm can wear out prematurely, from cavitation inside the valve. “But, if it’s a good quality valve, it should last 12-15 years out in the field.”
“When a valve malfunctions, 80 or 90 percent of the time, it’s going to be something on the inside of the valve itself,” said Osbaldo Ojeda, owner of First Utah Landscaping, LLC, in Salt Lake City, Utah. “There’s a diaphragm, and a spring, and another couple of pieces of plastic that control the flow. It’s usually going to be one of those parts.”
When a valve fails, it’s often because of its solenoid.
There are two basic types of solenoids: the 24-volt and the DC-latching type. The DC-latching solenoids are found in the battery-powered valves that are used where there is no access to AC power.
“The most common electrical problems are bad splices, and the second are solenoids,” said Kurt K. Thompson, owner of Kurt K. Thompson and Associates, LLC, a consulting and training firm. That’s partly because of the way solenoids are made, and partly because of how they work.
Essentially, a solenoid is a hollow plastic tube, wrapped with hundreds of feet of very fine wire. When the controller sends voltage down to this wire coil, it creates an electromagnetic field that pulls a little plunger inside the tube up and down.
It’s like a finger that plugs and unplugs the port. When it moves up, it unplugs the port, and water pushes the diaphragm open. When it moves down, plugging the port, the opposite happens. “Due to the nature of the beast, friction causes heat to build up inside solenoids, and they can short out over time,” said Thompson. “Luckily, they are super simple to replace.”
Dos and Don’ts:
There are some important things to do, and to avoid doing, when installing valves. The first one is, do use a big enough valve box. “For us, the minimum we would use is a 12- inch for electric valves,” said Hunt. A 6-inch box is for splices, not valves.
Valve boxes are made in a variety of sizes. “People will cut down a box sometimes, because they dug their trench too shallow,” said Hall. “Get the pipe at the right level, and you won’t have to worry about that.”
Don’t cram too many valves into a box. “This can really cause headaches,” said Hunt. It’s always best to allow room between valves, and between the valve and the walls of the valve box, so the valves can be efficiently serviced, which reduces the cost of regular maintenance.
Don’t use ‘pipe dope’ to seal valve threads. Wolfarth says that a high percentage of those products, even some that claim to be safe, contain chemicals that attack plastics. It weakens them, and can cause failure of the threads or fittings very quickly, sometimes overnight.
“While there are many sealants on the market that will work, and indeed are okay for use on plastics, it’s far safer to use PTFE (Teflon) tape. Let the tapered threads do their jobs by inserting the fitting into the valve until hand-tight, then do one full turn with a wrench.”
Don’t cut the wires connected to the solenoid wires too short. “Coil at least two feet of control wire around the solenoid,” said Hall. “That way, when you need to unscrew the solenoid to service the valve, you can actually take it out and lay it on top of the ground. A lot of times, you see these short wires in the valve boxes, and you can’t even unscrew the solenoid, because it’s pulled so tight.”
Some contractors believe that wrapping extra wire around the solenoid creates a surge suppressor that will protect the valve against lightning strikes. Wolfarth says that’s a myth. If you’re installing in a lightning-prone area, find some better means of protecting the irrigation system.
Do use waterproof connectors. For commercial jobs, Hunt uses the industry-standard 3M DBY connector.
On the residential side, he uses a couple of different products. “Mostly, we use a snap-together wire nut with a jelly-filled cap. You just press the cap down onto the connector, and they click tight together. We don’t use a lot of wire nuts or twist-ons.”
In situations where sand or silt is in the water, do place a filter on the line. Where it’s placed is important. “Typically, a filter is put in downstream of the valves in a lateral system, so that we can service it easily,” said Hall. “But, to filter what’s going into a valve itself, it’s best to put the filter right at the point of connection.”
Do put geotextile filter fabric on the bottom of the valve box, and then rock applied on top of that. “We use number 57 stone, drainage rock, in the base of the valve,” said Hall. “It keeps mud, sediment and debris from clogging the solenoid ports.”
We all know that we need to keep our hearts healthy. The same goes for the hearts of irrigation systems. Keep those valves healthy, and they should go on performing well for many years to come.