Mastervalve / Flow Sensor
Automated emergency shut-off devices save water by automatically shutting off the water when something in the irrigation system breaks. The first of these devices is a irrigation controller with the capability of monitoring flows. The controller works in conjunction with a flow sensor and master valve. The master valve is an electric solenoid valve that is installed on the mainline near the water connection point, where it can shut-off all the water flowing to the entire irrigation system. The master valve is typically installed right after the backflow preventer.
Here’s how it all works: When water flows into the irrigation system the flow sensor measures the rate of that flow. The controller is set in learning mode, where it monitors the flow sensor output and memorizes how much flow occurs at any given time of the day when everything is working correctly. Once it has a history of correct flows, it then monitors the flow at all times and compares the current flow with what is normal. If it detects an abnormal flow (either too high or too low), it signals the master valve to close. This shuts off water to the entire irrigation system. Most of these controllers will then sound an alarm to alert you. Some will even phone you, email you, or send a text message with an alert. So if a mainline were to break, the flow sensor would show a higher than normal flow, and then the controller would respond by closing the master valve, shutting down the entire system, and alerting you. Most of these controllers will also detect a valve that is broken, as well as any number of other problems.