Flow Switches

A flow switch is a device that monitors the rate and pressure of liquids, air, or other gaseous media moving through a duct, system, or loop. It is also known as a flow sensor or flow indicator. These switches or sensors may be set to measure flow during a specific time period or to monitor overall flow continuously. A flow meter or indicator is not usually a true flow switch; if the device records and displays data, it is better referred to as a meter or indicator.


How Does a Flow Switch Work?


To understand how a flow switch works and what it does, it's helpful first to identify the essential components of a typical flow switch or sensor.

The main device (a paddle or magnetic trigger of some type) is connected to a circuit and positioned in the channel through which liquid or gas flows. The material passing by moves or rotates this paddle, which delivers a signal reading to a secondary component known as the transducer.

The transducer transforms the raw signal from the paddle and transfers it to the transmitter. The transmitter then compares this reading to a set of parameters and delivers whatever signal or action is required to modify the behaviour of other components and systems.

Flow switches may therefore monitor, report on, and regulate liquid or gas flow rate via a specific component of a system or the whole system, ensuring that flow stays within pre-set parameters. If the rate exceeds or falls below what is required, several activities, such as raising an alarm, activating a pump, diverting flow, and shutting down system components. The actions of a switch are entirely dependent on the kind of switch and the purpose for which it was designed.

A tactile paddle will not be found on every flow switch. Ultrasonic and other non-intrusive counterparts, which work by reflecting a signal off the substance being monitored, are also widely used. This is particularly useful when the medium is contaminated, physically hazardous, or otherwise poisonous, or when having no moving components exposed to continuing wear and tear is preferable.

Rotaflow sensors are simpler devices that measure, restrict, or allow the free passage of a gas or liquid via a tapered tube with a float (or occasionally an electromagnet). Magnetic flow switches are available in a number of designs and may be highly effective in a wide range of applications as long as the medium is somewhat conductive.


Flow Switches Applications


1. Flow Switches for Boilers:

Both water and gas pipelines may have boiler flow switches. Water channels are often designed to keep the boiler from operating under low or no flow conditions. The primary purpose of gas boiler flow controls is to prevent the boiler from starting before any gases have evacuated down the chimney through fans.

2. Flow Control Switches for Pumps:

A pump flow switch is often installed to prevent the pump from running dry in the event of a water supply failure. Because water pumps may quickly overheat or become damaged if left running in low/no flow circumstances, flow switches for pumps often function to cut off the energy to the pump when it isn't getting enough liquid.

3. Flow Switches for Shower Pumps:

A shower pump flow switch helps to maintain the water pressure pushed via the pipework and out of the shower head. They have a mechanical design and may be found on both hot and cold supply channels. The switch is activated when there is a demand for water at the shower head, which completes a circuit and instructs the pump to start functioning. Shower pump flow switches may degrade with time due to limescale, heat, and other reasons and may eventually need to be replaced.


PVL Flow Switches


Pressure Vacuum Level Ltd has been selling high-quality flow switches for over 28 years. PVL provides these devices for various industries.

Don't hesitate to contact us if you have any questions about our flow switches or other products.


Other Products


PVL customers can rely on us for high-quality products. Flow Switches are only a handful of the products we provide customers across the United Kingdom. We are also a significant supplier of Pressure switches and Transducers.



  • For domestic 15mm or 22mm pipes
  • 0.8-6 l/min switching range
  • 15mm / 22mm compression fittings
  • Rated to 8 Bar pressure
  • User adjustable

  • 0 - 500V 15Amp S.P.D.T switch or;
  • Low Voltage model also available ('RL' model)
  • Polypropylene or 316 Stainless models
  • Switches available with 3/4" & 1" BSP & NPT threads
  • Manual override built in to all 'F-H' models
  • Modular construction
  • High pressure 400 Bar 5800 psi models available
  • Seal-less magnetic drive
  • Weatherproof IP67 housing
  • Easily serviceable
  • 4 x paddles supplied with each switch
  • Pipe sizes from 25mm to 200mm
  • 1”BSP threaded pipe fitting
  • Brass or stainless steel option
  • 0.9 - 6.7 m3/h H2O switching range
  • C/O Micro-switch Rated 250Vac/5A
  • 4 x paddle supplied with each switch
  • Pipe sizes from 1” to 6” diameter.
  • Standard 1” BSP fitting
  • 0.19 to 39.90 m³/h switching ranges
  • Brass or stainless steel body
  • C/O Micro-switch Rated 250Vac/15A
  • For 25mm pipe sizes
  • Detects low flows from 0.1 l/min
  • 1”BSP connections
  • Pressure up to 100 bar
  • Max Flow 100 l/min
  • Reed switch or relay option
  • Nominal pipe sizes 10-50 mm
  • 3.5 - 69 l/min switching range
  • 3/8” - 2” BSP threaded connections
  • Low pressure loss
  • Brass or stainless steel option
  • C/O reed switch rated at 230Vac/1A
  • 0 to 500V AC 15 Amp S.P.D.T switch
  • 316 Stainless Process Connection
  • Super Tough Billet Aluminium Housing
  • Manual override built in
  • 3/4” & 1” models available with BSP or NPT threads
  • 400 Bar (5800 psi) pressure rating
  • Seal-less magnetic drive
  • Dieselene & High Temperature versions available
  • Weatherproof IP67 housing
  • Easily serviceable
  • For 15mm to 25mm pipe sizes
  • Detects flows from 2.5 l/min
  • 1” BSP Threaded and PVC push fit
  • Pressure up to 18 bar
  • No metal wetted parts
  • 100 l/min max flow
  • Nominal pipe sizes 8-25 mm
  • 0.1 - 80 l/min switching range
  • 1/4” - 1” BSP threaded connections
  • Pressure 200 bar (500 bar option)
  • Brass or stainless steel option
  • Viscosity compensated version(HD2K)
  • Nominal pipe sizes 10-50 mm
  • 4 - 93 l/min switching range 3/8” - 2” BSP threaded connections
  • Low pressure loss
  • Brass or stainless steel option
  • C/O micro switch rated at 250Vac/5A
  • Universal input for unit signals
  • Pt100, thermocouple, potentiometer, switchable via front-side DIP switch
  • 1 or 2 relay outputs
  • Universal relay connection
  • Adjustable min/max contact function
  • Actual value output 4 .. 20mA
  • 2-colour illuminated scales for limit value adjustment, colour depends on switch status
  • With Pt100 sensors, monitoring of sensor break and short-circuit
  • Wide-range mains adapter or 24 V DC
  • Functional safety up to SIL2
  • Housing width 12.5 mm
  • Removal coded terminals
  • Carrier rail mounting TS35 EN60715
  • Safe galvanic isolation between input / output / auxiliary voltage
  • Momentary value indicator and totalisation
  • Pulse output with adjustable pulse per volume
  • Antivalent outputs
  • Analogue output of the momentary value
  • Simple guided menu via graphics display
  • For 32-50 mm pipe size
  • 2-220 l/min switching range
  • 1 1/4” - 2” threaded connections
  • Brass or stainless steel option
  • Pressure up to 200 bar
  • Viscosity stabilised
  • For 15 mm nominal width
  • 0.4-12 l/min switching range
  • 1/2” male threads
  • Integrated filter
  • Plastic wetted parts
  • Up to 10 bar pressure
  • For 15 mm pipe size
  • 1 l/min switching point
  • 1/2” threaded connections
  • Bi-directional flow switching
  • Pressure up to 300 bar
  • Viscosity stabilised
  • Nominal pipe sizes 8-25 mm
  • 0.1 - 80 l/min switching range
  • 1/4” - 1” BSP threaded connections
  • Optionally side or top displays
  • Brass or stainless steel option
  • Viscosity compensated version(HD2F)
  • Nominal pipe sizes 8-25 mm
  • 0.4 - 60 l/min switching range
  • 1/4” - 1” BSP threaded connections
  • Pressure 200 bar (500 bar option)
  • Brass or stainless steel option
  • -20..+120 °C (-20..+150 °C option)
  • Nominal pipe sizes 8-25 mm
  • 1 - 11 l/min switching range
  • 1/4” - 1” BSP threaded connections
  • Not affected by dirt
  • Brass connection material
  • 230Vac/0.5A reed switch
  • Intrinsically safe use of Pt100 sensors
  • Intrinsically safe use of 0(4)…20 mA sensors
  • Intrinsically safe use of 4…20 mA, loop-powerd indicators
  • Measuring range 0..50 Ω up to 100 kΩ
  • Processor technology with 12 Bit AD/DA-converter
  • Teach-in programming for start- and end-value    
  • Increase or decrease output characteristic programmable
  • Operation mode indicated by use of a 2-color LED
  • Measuring range 100 mbar to 10 bar
  • Immersion depth: max. 100 m
  • Analog output 4..20 mA
  • For drinking-, process-water, oil
  • Process temperature -10..+60 °C
  • Protection class IP68, depth of immersion max. 100 m
  • Flow transmitter for water and other liquids with integrated temperature measurement
  • Fast response timeIntegrated volume meter with preset
  • Measuring method without moving parts, no wear
  • Stainless steel material coming into contact with medium
  • 1 analog output (20 mA / 10 V)
  • 2 versatile configurable switching outputsIO-Link interface
  • High-resolution graphic LCD Parameters programmable with multifunction ring
  • Waterproof all-metal housing (IP67)
  • Mineral glass front, scratch-proof and chemically resistant
  • Can be used on site for: parameter modification, firmware update, adjustment of inputs and outputs
  • Can be connected via USB
  • 1/4” or 1/2” Screw in connection
  • 2 - 150 cm/s metering range
  • 4-20 mA or 0-10V output
  • PNP / NPN switch output
  • All stainless wetted parts
  • Fast response times
  • Nominal pipe sizes 8mm to 25 mm
  • 2 - 80 l/min switching ranges
  • 1/4” -1” BSP threaded connections
  • Maximum temperature 100 °C
  • Viscosity stabilised option (NJV)
  • Brass or Stainless Steel
  • For 6 mm to 20 mm pipe sizes
  • Detects low flows from 0.30 litres per hr
  • 3/4” BSP unions with PVC push fit
  • Vertical Installation only
  • No metal wetted parts
  • Suitable from 1 to 14 liquid PH level
  • Nominal pipe sizes 32-50 mm
  • 15 - 80 l/min switching range
  • 1 1/4” - 2” BSP threaded connections
  • Pressure 200 bar
  • Brass or stainless steel option
  • Lower Pressure Loss
  • Nominal pipe sizes 32-50 mm
  • 10 - 150 l/min switching range
  • 1 1/4” - 2” BSP threaded connections
  • Pressure 200 bar
  • Brass or stainless steel option
  • Lower Pressure Loss
  • Nominal pipe sizes up to 80mm
  • 10 - 268 l/min switching range
  • Welded connection (others available)
  • Low pressure loss
  • Brass or stainless steel wetted parts
  • C/O Micro-switch Rated 250Vac/5A
  • Adjusted to switch between 0.015 and 0.4 l/min H2O
  • Sizes from 1/4″ to 1/2″ BSP
  • Low pressure loss design
  • Bronze body
  • Reed switch rated at 250Vac/1A 50VA
  • Can be used with liquids and gases
  • Nominal pipe sizes 8mm to 15mm
  • 0.4 - 12 l/min switching ranges
  • 1/4” -1/2” BSP threaded connections
  • Pressure up to 200 bar
  • 20 l/min max flow
  • High switching power
  • Nominal pipe sizes 8mm to 40mm
  • 0.4 - 90 l/min switching ranges
  • 1/4” -1 1/2” BSP threaded connections
  • Medium Temperature -20 °C to 110 °C
  • 150 l/min max flow
  • Lower Pressure Loss
  • Multi Voltage Operation
  • 10 Programmable Timers Built In
  • Powerful 40Amp Solid State Drive
  • Dedicated 16A Alarm Relay Detachable Electrical Housing
  • 18 Bar 261 psi Rated Standard Model
  • 200 Bar 2900 psi Model Available
  • Suits Pipes 1” & Larger
  • Accepts 2 Remote Inputs
  • Weatherproof Housing
  • Particularly suitable for extremely high flow rates
  • Extremely fast response time: 100 ms
  • Measures flow, total consumption, temperature and pressure
  • Measurement at high temperatures – max. 200 °C
  • Measurement in various gases by selecting gas type, on request
  • Can be used in pipes from DN 20 to DN 500
  • Installation via 1/2″ ball valve under pressure
  • RS 485 interface (Modbus-RTU), 4…20 mA, pulse output as standard
  • From 0.4 to 100 l/min flow ranges    
  • Very fast response time    
  • High Overload Protection    
  • High Max Flow    
  • Low pressure  Loss    
  • Compact Design    
  • 150c High Temperature Option    
  • 100 bar High pressure Version Available
  • For 20mm pipe sizes
  • Detects low flows from 0.065 l/min
  • 3/4” BSP unions with PVC push fit
  • Pressure up to 18 bar
  • No metal wetted parts
  • Reed switch or relay option
  • For 15 mm pipe sizes
  • Detects low flows from 0.1 l/min
  • 1/2” BSP connections
  • Pressure up to 100 bar
  • Max Flow 30 l/min
  • Reed switch or relay option
  • Nominal pipe sizes 15-25 mm
  • 1 - 11 l/min switching range
  • 1/2” - 1” BSP threaded connections
  • Not affected by dirt
  • Plastic connection material
  • 230Vac/0.5A reed switch
  • Suites Open channels or Pipework
  • 0 to 500V AC 15 Amp S.P.D.T switch
  • Works when solids or slurry is present
  • Weatherproof IP67 housing
  • Perfect for high velocity flow
  • ¾” & 1” BSP models available