Which Flow Sensor Is Right for Me?
Flow Sensors
The simple truth is that all flow sensors are not created equal. Understanding your application requirements, knowing building codes for sensor materials, recognizing the pros and cons of sensor technology, and realizing that you may need other devices to connect the sensor to the irrigation controller are important factors to consider when choosing a flow sensor.
Here’s what you need to know in order to choose the correct flow sensor for your needs.
The Differences Between ELF & FSI Flow Sensors
Your first step in choosing a flow sensor is to understand if your application requires an ELF flow sensor or an FSI flow sensor. There are key differences between these two major categories of flow sensors to consider. Here’s a quick breakdown.
What Are ELF Sensors?
ELF (Enhanced Low Flow) sensors are ideal for most residential systems, as well as residential or commercial drip systems. These low flow sensors are useful in zones with low flow rate zones such as smaller landscape areas, green spaces, green roofs, or internal building use in atriums, planters, or hanging baskets.
CST’s ELF sensors can connect directly to the master valve and don’t require straight pipe lengths before or after the sensor, allowing for simple installation. Our ELF sensors are designed to be compact to fit small, tight spaces and may be mounted in both horizontal or vertical orientations.
Our ELF series sensors are available in two sizes to meet a range of needs:
- 1. ¾ Inch PVC Sensor with Socket Type Connections
- Flow Measurement Range: T75 Version: 0.20 – 10gpm
- 0. 1 Inch Sensor with Male Pipe Thread Connections
- Flow Measurement Range: T10 Version: 0.20 – 20gpm
ELF series sensors feature a digital output signal compatible with most smart irrigation controllers. They are also available with a scaled pulse output, or SP3 models. These ELF series SP3 sensors are ideal for use with Hunter Hydrawise controller models. Either version can measure a wider range of flows, operate with lower pressure loss, and maintain a working pressure rating of 240 psi. All CST ELF series sensors are also backed by our lifetime replacement guarantee if the flow sensor fails due to moisture intrusion.
What Are FSI Sensors?
FSI (Flow Sensor Insert) sensors are ideal for complex or larger irrigation systems including office/business parks, schools, multiple property management, or HOAs. CST’s FSI sensors incorporate a variety of different styles of sensors including PVC tee flow sensors, brass flow sensors, and saddle flow sensors.
PVC tee type flow sensors are ideal for:
- Mainline pipe diameters when the sensor can be glued to the pipe
PVC flow sensors are available in the following sizes:
- 1 inch PVC Tee Type Sensor with Socket Connections
- Flow Measurement Range: T10 Version: 0.85 – 52gpm
- 1 ½ inch PVC Tee Type Sensor with Socket Connections
- Flow Measurement Range: T15 Version: 1.8 – 108 gpm
- 2 inch PVC Tee Type Sensor with Socket Connections
- Flow Measurement Range: T20 Version: 2.8 – 170 gpm
Brass flow sensors are ideal for:
- Use in building mechanical room applications where building code regulations, require metallic piping systems
- Increased durability for sensitive locations
Brass flow sensors are available in the following sizes:
- 1 inch Brass Bodied Sensor with FNPT Connections
- Flow Measurement Range: B10 Version: 0.8 – 50gpm
- 1 ½ inch Brass Bodied Sensor with FNPT Connections
- Flow Measurement Range: B15 Version: 3 – 90gpm
Saddle flow sensors are ideal for:
- Larger pipe diameters where the flow sensors can be clamped onto the outside of the pipe for ease of installation
- Compatible with PVC piping systems
Saddle flow sensors are available in the following sizes:
- 3 Inch FSI-S Series Saddle Flow Sensor
- Flow Measurement Range: S30 Version: 6 – 300gpm
- 4 Inch FSI-S Series Saddle Flow Sensor
- Flow Measurement Range: S40 Version: 10 – 480gpm
- 6 Inch FSI-S Series Saddle Flow Sensor
- Flow Measurement Range: S60 Version: 45 – 1100gpm
CST FSI Series flow sensors feature the same digital frequency output used by most commercial smart controllers, but are also available as SP3 models, compatible with Hunter Hydrawise controller models. Designed with CST’s impeller technology, FSI-T Series flow sensors can measure a broad range of flow from 0.8 gpm to 1100 gpm. Similar to the ELF series, the FSI-SP3 models are also backed by our lifetime replacement guarantee if the flow sensor fails due to moisture intrusion.
All CST flow sensors may be installed at any orientation, horizontal, vertical, or radially, around the pipe to allow service in complex piping systems. Additionally, CST sensors may be left in place for the winter in cold climate systems. There is no need to remove the sensor tee or insert from the piping system to winterize.
Multiple Benefits of Impeller Technology in Flow Sensors
There are many ways to detect liquid flow in piping systems. Technologies include positive displacement, rotating propellers, turbines and impellers, nutating disks, and other mechanical devices. There are also various technologies without moving parts such as pressure differential, vortex shedding, Coriolis effect, acoustic (ultrasonic), and magnetic. Every technology has been developed for a specific purpose and may excel in accuracy, flow range, durability, ease of installation, cost, or some other desired parameter.
However, every technology also has its shortcomings. A highly accurate precision meter may not have as wide a range of flows or may require expensive or timely maintenance. An electronic meter without moving parts may be difficult to troubleshoot and many must be completely removed from the pipeline to clean or service. The last choice may be the 100-year-old mechanical technology of a domestic water meter. They have a limited range of flow, large pressure losses, can’t be left in place in cold climates and wear quickly in non potable water.
At CST, we use impeller technology to detect flow. Why? Because, with almost 40 years of experience in manufacturing, selling, and servicing flow meters and sensors of all types, we believe the impeller type flow sensor is the best technology for this application.
The impeller sensor is simple, it has one moving part and is properly designed, can detect extremely low flows, a wide range of flows, has very little friction loss, and is easy to service in place. CST has taken the technology and properly designed a sensor that is mechanically suited for the irrigation environment and electronically suited for the flow measurement requirements of irrigation systems. CST sensors are easy to install and service, cost effective for the market, feature multiple output signals to interface with all known smart irrigation controllers, and offer proven reliability backed up by a lifetime warranty.
At CST, we’ve been designing and manufacturing flow sensors for over 15 years and have the options available to help you choose the best flow sensor technology for your irrigation system.
CST Transmitters Solve Installation Problems
CST flow sensors are compatible with any smart controller with a flow sensor input. However, some installations require more than one flow sensor or need to share a flow sensor among multiple controllers. Often, on retrofit upgrades, running wire for a flow sensor and master valve is prohibited by the high cost of crossing pavement, hardscapes, or established landscapes. Fortunately, CST has transmission devices to overcome these obstacles.
The CBF-102 Combiflow is a wired control device that connects two flow sensors on different POCs (points of connection) to a single input channel control device. The Combiflow is programmable. The connected flow sensors may vary in size and style. It will combine the different flow rates of the sensors and transmit the signal to the connected controller. It will accurately send flow information from one sensor, the other sensor, or both.
The Isoflow 304 is a wired signal transmitter that enables one flow sensor to provide flow information to four separate irrigation controllers. It also provides an isolated master valve power output, allowing up to four controllers to operate one solenoid-operated master valve, eliminating the need for relays.
The Pathway S01 is a patented communication system that allows a CST sensor and a solenoid actuated master valve to be retrofitted to an irrigation system, utilizing existing zone valve wires to carry data and valve control signals to the irrigation controller. The Pathway S01 provides a cost-effective method to add flow monitoring and control to existing irrigation systems where pavement, hardscape, or other landscape features make conventional wiring prohibitively expensive.
The DFM Series 6300 Flow Monitor features a digital display and is compatible with CST’s FSI series flow sensors. It is available as a panel mount or mounted in a protective enclosure for wall mounting. The display can be programmed to show flow rate, total, or grand total, and the secondary display can be programmed to display flow rate, total, grand total, engineering units, custom legends, or can be turned off. The DFM 6301 Model is equipped with a 4-20mA analog output to transmit flow rate and two, C form relays that may be independently programmed as high or low flow alarms, pulse outputs, or totals.
CST transmitters are designed to work with all CST flow sensors. While they may work with other flow sensing devices, we strongly recommend using CST sensors only.
The CST team has the knowledge and experience to help you choose the flow sensor matched to the corresponding smart irrigation controller to meet your specific needs. Whether you need an ELF or FSI sensor, brass or PVC construction and have a single property or multiple properties to manage, we offer the high-quality products you need to improve your water management system.
Ready to order your flow sensor? Contact us today!