You’re thinking about converting your current multi-zone lawn irrigation system into an electronically-controlled model with control and relay set-up for the pumps. But you’re concerned that if one of the valves that’s part of the system fails to open, then you might have a problem with too much pressure which could damage the pumps. You wonder — what kind of set-up would help to shut off pumps in the absence of pressure or flow?
Flow sensors with paddle wheels exist that can actually measure the flow rate in the pipes in gallons per minute (GPM) or cubic feet per minute (CFM). However, they do require that you have a specialized irrigation controller that can work with them. This may mean that you need to upgrade your current controller.
The irrigation controller measures the flow and compares it to the pre-programmed flow that should be present in the system for the valve that is currently open. The controller then makes a decision based upon that measured amount. If the flow is too low or too high, it can shut down pumps or close the master valve that shuts off the water to the entire system.
The sensors themselves should be installed in a tee on a straight length of pipe. The length of the straight pipe should be approximately five times the pipe diameter before the sensor and five times after it. The reason for this is to reduce water turbulence in the pipe which can cause inaccurate pressure readings.
You can also use a pressure sensor and pump logic controller to turn off the pumps at high pressure or very low pressure. It’s important to be aware that the sensor is a little different from the typical pressure switch. A standard switch turns the pump on at low-pressure and off at high pressure. The logic controller is basically used as a detector and timer.
You should also know that it’s normal to have a pressure spike as the system changes from one valve to another. This is because it defeats the purpose of the setup if the pump shuts off during the switch of valve zones. You also need a delay to allow the pump to start up since there will be no pressure until it gets going. The pressure sensor also needs to be on a straight pipe section, just like the flow sensor.
Lawn irrigation systems can present a host of challenges to novice landscapers. South Austin Irrigation can help you reconfigure old systems with a minimum of hassle and a maximum of cost efficiency. When you need expert advice and service, contact us!