There's a small instrument on your car dashboard that's given very little attention but is essential to the efficient operation of your car - the speedometer. We look at it numerous times while driving, check it when we need to know how far we've traveled, calculate gas mileage from it and even set our cruise control by it. Its importance becomes obvious once you think about it.
The irrigation industry has a similar device: flowmeters.
Flowmeters measure the flow of water and the amount used. They help to conserve water, make irrigation more efficient and assist in trouble-shooting problems. Like speedometers, they may be given very little attention, but are essential to the efficient operation of an irrigation system.
Flowmeters give an exact and immediate measurement of water being used. In high maintenance areas where careful watering is important, such as golf course turf or playing fields, flowmeters help achieve optimum watering conditions. They tell you how many gallons are used for a specified area, so that you can calculate the exact number of inches of water that you lay down.
The most obvious and common flowmeter is the municipal water meter placed at the head of your water main. Today, there are many types of flowmeters. They range in pipe size from ? inch to 48 inches. They may have dials or digital readouts and they can be read at the meter location or at a remote monitor placed somewhere else. Some flowmeters are connected to the controller of watering systems and others are used in computerized systems to help make complex decisions.
Norm Bartlett, of Data Industries, says that virtually every landscape contractor who tries to conserve water has some form of flowmeter. You can't set a goal to conserve water unless you know how much water is being used. Water is getting scarce, especially in cities.
Water allocation remains the same for most populated areas, but the population keeps growing. Tighter restrictions on water usage all over the country are making careful monitoring a priority. Carlos Figueroa, of McCrometer, noted that during the recent drought in Texas, the demand for flowmeters jumped dramatically. Irrigation managers want more accurate and useful information about how much water their systems use.
For many applications, just reading the municipal water meter may give you much of the necessary information. On larger systems, with different watering requirements, separate flowmeters can be used to more accurately determine how much water is required and how much is actually used.
Water conservation involves setting goals to reduce water usage and testing the results of conservation methods. Fine tuning the irrigation system is of little use unless you get accurate measurements of the results.
There may be situations where there are no water meters, such as when you are pumping from a ground water source or a pond. In many water districts you need to report and pay for ground water. Here you may have no choice about using flowmeters; local or state agencies require it. Regulations aside, flowmeters keep you out of the dark about the amount of water used. When pumping from a ground source, people often split the pipeline, with part of the water directed for immediate use and the other line sent to a storage area such as a pond. In this situation, you may want to use two flowmeters to determine how much water is being used in irrigation and how much is stored.
If flowmeters had one specialty, it would be that they are great at detecting problems in the watering system. Better yet, with the right equipment they are very effective at helping keep problems small before costly damage occurs. Broken water mains, damaged sprinkler heads, leaky valves or stuck valves can easily be detected by flowmeters. They work by detecting a higher than normal rate of water flow. If your system normally waters at 450 gallons per minute and one night it waters at 550 gallons a minute, you know you have a problem.
Flowmeters not only detect leaks in a system; they can be used to shut the system down when a problem occurs. This type of flowmeter has two parts to the system. There is a flow sensor and a receiving device. The flow sensor, inside the pipe, is a paddle-wheel type device with a magnet. With each spin an electronic pulse is sent to the transmitter. The sensor does nothing but spin and send out a signal. This information is used to calculate the speed of the water flowing through the pipe. The system factors in the diameter of the pipe and formulates the water flow, 450 gallons a minute, for example.
The flow sensor transmits this signal to a receiver, typically located at the watering system controller. The receiving device is commonly a digital monitor with an electronic interface that connects the information to the controller. The best use of this flow sensor is to connect it to the watering system controller. Some companies, such as Data Industries, make interface devices that will take information from their flow sensors and convert it to a signal that will work with all the different brands of controllers. With this interface, you can program the controller to respond to abnormal watering conditions. The night your system shoots from 450 gallons per minute to 550 gallons a minute, the programmed controller will shut the system down.
More advanced systems using computers with flow sensors can make prioritized choices when detecting problems. In these systems, you can have watering zones with different priorities. The computer, when getting a signal from the flow sensor detecting a problem, will shut off the lowest priority level of zones. If shutting off that zone doesn't solve the problem, it will cut off the second level of zones, then the next. Say you have flowers, turf, and shrubs on different zones in that order of priority. When a problem occurs the computer would shut off the lowest priority, the shrubbery; then if the problem were still detected, it would shut off the next tier, the grass, leaving the flowerbeds until last.
Another advantage of flow sensors is that they can detect water that flows too fast through a pipeline. When water flows at more than ten feet per second, a valve that suddenly shuts down can create a "water hammer" effect. This could be destructive to the system. Flow sensors can report to the controller if this high velocity situation occurs and help prevent any possible damage.
Flowmeters are also useful in the process of spreading fertilizer through the irrigation system. This fertigation process is more accurate with a flowmeter because it shows how many gallons of water are mixed with the fertilizer. Otherwise, mixing fertilizer based on the amount of time the system is on could turn into a guessing game in order to achieve the specified mixture of water and fertilizer.
As a convenience, some landscapers find it easier to deal with gallons used, rather than minutes the system runs. For this reason many watering system controllers are now coming out with programs based on gallons rather than minutes.
Costs for simple flowmeters, or a flow sensor and monitor package, start at around $700. Landscape designers generally agree that flow sensors tied into controllers are the best applications of flowmeter technology. Since that combination costs more than just flowmeters, they are not typically used on smaller systems, those with less than a 2-inch water main.
One thing all landscape designers agree upon is that flowmeters, in some form, are essential for conserving water and creating productive, problem-free irrigation systems.