Backflow PreventionRead about this subject at backflow testing in Atlanta
Also known as a “sprinkler clock or timer”, its function is to control when the system starts, ends, and how long each irrigation-controller of the irrigated areas gets watered. There are few basic types of controllers.
1. Mechanical: Before digital timers came on the scene in the 1980’s, all irrigation clocks were mechanical. The day of the week, time of day and watering start times were dependent on motors turning gears. These are not as as accurate as the circuitry in digital controllers but “close enough” for the system to function. Due to the decay of the plastic gears used and the motors getting old the settings would change. Some of these such as the Richdel and Lawn Genie controllers would come with pins and six day watering settings where you could not set the watering to begin on a specific day of the week as now required in many municipalities. You were limited to every other day, every third day, etc. Another common type of mechanical controller is the “on|off” type used with indexing valves which are often connected to a well pump. As an indexing valve requires a delay in water pressure to rotate the disk, this type of clock sends a signal to a solenoid master valve which actuates the indexing valve. Using the multiple start time features on a digital controller the master valve in this type of setup can also be utilized.
2. Digital: Digital controllers provide far more accuracy and sophisticated programming than the older mechanical types. Some water districts no longer allow mechanical sprinkler controllers to be installed on newly constructed systems. A commonly used feature in these modern controllers is the “water budget.” This allows the controller run times for all the stations to be adjusted globally. You can decrease the zone run times across every station as a percentile from this one function. This is convenient for changing the amount of water applied to meet the landscape usage demand by season or time of year. These type of controllers are also very easy to program for multiple run times. Multiple start times are helpful in applying water in consecutive stages which can help to avoid run-off and deep percolation which concentrates the water use in the root profile.
If you think of the controller as the “brain” of the system, the valves would be the “heart.” In order to supply water irrigation-valve to the sprinkler heads a valve needs to be opened. These can be solenoid activated, pressure activated (such as indexing types) or manual such as a gate valve or separate water meter. How manual valves work is obvious so we will concentrate on automatic valves.
1. Solenoid Activated: These are the most commonly used type of valves. They consist of three main parts; a body, a diaphragm and a solenoid. Hydraulic automatic valves do not have a solenoid and we will touch on these briefly later as they are not used as much as they once were. The basic principle of this type of valve is as follows: The copper coils on an electric solenoid are activated as a magnet when the controller supplies current to that valve via a common and station wire. This pulls the metal plunger up into the solenoid which then no longer covers the outlet port in the body. The upper chamber of the body, separated by a diaphragm, no longer has a slightly higher PSI than the lower due to its slightly larger volume. This change in PSI pushes up the diaphragm and the static mainline pressure in the larger chamber is now dynamic and fills the upper chamber which flows into the lateral PVC pipe. As you can imagine, a lot can go wrong here. There are many ways that a solenoid valve can fail, but the consequences are only three. The valve won’t open, the valve won’t close, or the valve won’t close all the way (also known as a weeping valve.)
a. Valve won’t open: This could be the valve, or it could be the solenoid, field wiring or water supply. It could also be a pipe or head break in the area (zone) covered by the valve. We are going to assume that you do not know where the valve is located, so before going through the trouble to find where it is buried we will check the water supply first. Will other zones turn on and from the controller? If so, more than likely it is not the supply. If you know the area covered by the zone look for leaks. Are any of the heads dribbling water? If so you may have a leak or a valve not fully opening. Once you rule those problems out, check the controller. Unhook the common and the station field wire and check the voltage at the wire terminals. Do you have 26 or more volts? If so it is not the controller. But just to play it safe, hook the problem valves field wires to another station terminal on the clock. If the malfunctioning valve comes on you have a controller problem. Check the ohms of the solenoid using common and field wire. They should read between 20-60 ohms (Rainbird solenoids tend to read around 50-60.) Much higher than that and you likely have a bad solenoid, a high resistance splice or cut or corroded wire. Now we need to find the bad valve. This is best done with a wire tracker, but can be done (sometimes) manually. See this article. Once you have found the valve, open it manually. This can be accomplished by either loosening a bleed screw or slowly turning the solenoid counter clockwise. This will release the pressure from the upper chamber. If the valve comes on the problem is electrical. Note that if you have a pump start system the pump needs to be running to do this, just turn on a working zone so that the mainline is pressurized. Often in electrical problems the wire splices on the solenoid have gone bad. Cut off the wire nuts, strip all the connecting wires back a half of an inch. Turn the valve on from the controller and check the voltage on the common and field wire. If they read 26 volts plus, turn off the controller and connect the wires without wire nuts and check again. If the voltage has dropped significantly you have a faulty connection electrically upstream. If your voltage and wiring are good you should hear a click when you connect the wires and the clock is sending voltage. If all your electrical tests read good, most likely you have a faulty diaphragm or clogged outlet port. Remember to never open a valve under pressure. The spring or plunger can fly out and hit you in the eye, besides losing parts in the lawn or mud.
b. Valve won’t shut off:: Almost always a bad diaphragm. However I’ve also seen loose solenoid or bleed screws, leaks where the upper chamber screws on the lower chamber (also known as the bonnet) and in rare cases a damaged controller sending voltage when not scheduled to turn on that zone. I’ve also been called out for a system “not shutting off” and the controller had re-set to the default time of day (12AM) and start time and of course the irrigation came on. Check your timer settings and either un-plug the external transformer from the wall or turn off the 120 volt breaker to the clock before assuming the valve has failed, and replace your back-up battery on digital controllers.
c. Weeping valve: Sometimes a valve won’t close completely and allows a small amount of water to continue flowing to the heads. This will show up as damp spots that do not dry up around the lowest elevation heads. This is caused by either a bad diaphragm or some debris caught up in the valve seat. Don’t just clean the valve, replace the diaphragm.
2. Indexing Valves: Basically all your zones run from one indexing valve. The valve is activated by water flow entering the top of the valve. The pressure from the water turns a rubber disk on a stem guided by a cam and slot mechanism to turn the disk opening and supply water to the lateral pipes. If it leaks, or doesn’t come on (after checking your supply line and/or master valve) just re-build it by replacing the disk, stem and cam assembly. Be sure to remove any roughness or build up inside the body as this can prevent the disk from fully turning. On some occasions I have been able to trim the outside of the rubber disk just a little with a razor to get the disk to spin. My advice though is if it fails in any way, re-build it. Don’t forget to replace the bonnet o-ring when re-building or it could start to leak.
3. Hydraulic Valves: Hydraulic valves are operated by water pressure not electricity. Instead of wires, each valve is connected to the controller by a tube. This tube is under pressure keeping the PSI higher in the upper chamber which keeps the diaphragm closed. The valve is opened when the controller release full pressure in the tube. Other than that the mechanics and repairs are very similar to electric solenoid valves. The main difference is that a tubing leak in the controller, at the valve or anywhere along the length of the tubing will cause the valve to open. It is for this reason and the difficulty in locating them in field has caused hydraulic systems to fall out of favor.
Continuing with the biologic analogies, the pipe, whether PVC or polyethylene would be the “veins” of the system. Although I have repaired poly pipe laterals, all of my irrigation experience has been in the southern U.S., where PVC is almost always used for laterals and mainline. Polyethylene is generally used in colder regions where the ground freezes deeper than down here in Florida. The main difference is that poly is connected using barbed or pressure fitting, and PVC is “glued” using solvent welding. All multi-zoned sprinkler systems have both mainline pipe and lateral pipe. Mainline refers to the water supply pipe to the valves, and lateral pipe refers to the pipe feeding the sprinkler heads. In a city watered supplied system the main line is always under pressure unless a master valve is used. A master valve is upstream of all the zone valves and opened simultaneously with the zone valve to supply water to the heads. A third type of piping is the “swing joints.” This can either be flexible pvc, poly or in some cases nipples and street els that connect the lateral pipe to each individual head. This is a preferred way to connect the heads as it often avoids damaging the lateral pipe when a sprinkler head is run over by a car or hit by a lawn mower.
There are many types of sprinkler heads. To keep it simple lets go the basics; rotors, fixed sprays and drip.
1. Rotors: Rotors rotate, hence the name. Typically they throw water much farther and are designed to water larger areas using less heads. There are two basic types; impacts and enclosed gear drives. Impacts rotors are turned by having the water from the nozzle impact or hit a spring loaded arm which turns the head. When adjusted to less than 360 degrees a collar initiates a ratchet to return the head to its starting position. Pop up impact heads are more maintenance intensive than enclosed gear drives due to the mechanism being exposed to dirt and grass. Here if Florida the St. Augustine stolons will grow into the gears and keep the head from turning. In my opinion I think these heads are best used on PVC stand pipes where they are less exposed to debris. Gear drive rotors are turned using water pressure to move gears that rotate the heads. As they are enclosed dirt and debris are seldom an issue. However they also will stop turning over time just due to wear and tear. Over the last ten years or so “spray rotors”, or “rotating nozzles” have become popular. I’ll talk more about these in the water conservation part below.
2. Fixed Sprays: Also just called “spray heads” these heads spray a pattern of water and do not turn. There are many distances and patterns to choose from to match the area watered. These can either be “pop up” which push a barrel out of the body and then retract or just a nozzle on a piece of PVC using a “shrub adapter” sticking up behind the bushes. Popups range in size from two inch to twenty four inch. Although four inch popups are usually installed in the turf, I believe six inch is a better choice. This is especially true in St. Augustine grass where the accumulation of thatch raises the level over which the nozzle needs to spray.
3. Micro Sprays: Micro sprays are low volume, low distance nozzles attached to a stake in the ground or modified to fit into a popup body. These are most often used in low water requirement areas such as landscape beds as an alternative to drip tubing. Due to the small orifice size both a pressure regulator and filter should be installed upstream to avoid high pressure misting and clogging.
Conserving Landscape Water
A subject near and dear to my heart let me state this upfront; we use way too much potable water keeping our conserving-water landscapes green and nice. Poor irrigation efficiency coupled with lax enforcement of what few weak water restriction, pollution and regulatory laws we have in effect (at least in Florida) results in millions of gallons of waste. Water management districts play too much politics with legislators cozying up to big business ( got sugar? ) to the detriment of water quality. I know everybody hates “big government”, but as a regulated and non-renewable resource only the government, passing laws it is willing to pay to enforce can save our water. There is not enough reclaimed water to irrigate all the homes and golf courses in Florida. Just because water is pulled from a well on your property doesn’t make it “free”, or even “yours” as water migrates through and under the ground in the state aquifers. Safe “no fertilizer” buffers need to be enacted and enforced near both fresh and salt water. I’ve seen lawn companies in Sarasota fertilizing along the intercostal waterway seawalls splashing half the nitrogen pellets into the river. I still see sprinkler companies mixing rotors, sprays and drip irrigation on the same zones, whether in the sun or the shade, even though they know it’s inefficient, because it is “cost efficient.” I guess it depends on how you measure “cost.”
The Sprinkler Repair Business
Yes, even after ranting above, I’m in the sprinkler repair business. No, I’m not angling for sainthood by saying this, but I do walk away from jobs where wasting water is the “less expensive” alternative to doing the job correctly. I seldom do “swimming pool re-do’s” where a pool is being added to a yard. Why? Correctly zoning the irrigation to avoid mixing sprays, rotors and drip is more expensive in the short run. Homeowners don’t mind going with low ball and bad irrigation proposals because there are many contractors who either don’t know better or don’t care. The contractor just wants the check for more marketing. In the long run though doing it the wrong way does cost more because your plants won’t thrive, you’ll keep dumping more weed killer in the grass, more fertilizer on the shrubs, and it won’t help your yard, but it will hurt us all when the lakes and rivers are dead.