💧 YF-DN40 Water Flow Sensor — 1½" BSP, 5–150 L/min (Hall Effect, DC 5V)
A 1½-inch (DN40) hall-effect water flow sensor for measuring flow rates from 5 to 150 litres per minute. Outputs a pulse signal proportional to flow rate — connect to an ESP8266, ESP32, Arduino, or Raspberry Pi to build a smart water meter, irrigation monitor, or pool flow tracker. DC 5V powered, 3-wire interface (VCC, GND, Signal). Ideal for mains water lines, borehole systems, pool returns, and high-flow irrigation.
Choose your flow sensor:
⚡ Key Features
- 1½" BSP Thread (DN40) — fits directly onto standard 40mm plumbing lines; suitable for mains water supply, borehole pump outlets, pool return lines, and large irrigation pipes
- 5–150 L/min Flow Range — covers everything from a slow garden tap to a high-flow borehole pump or pool pump return
- Hall Effect Pulse Output — each pulse corresponds to a calibrated volume of water; count pulses to calculate litres per minute and total consumption
- DC 5V Operation — 3-wire connection: Red (5V VCC), Black (GND), Yellow (Signal output)
-
ESPHome / Home Assistant — ESPHome has a built-in
pulse_countersensor; combine with a calibration factor to get L/min and total litres in your Home Assistant dashboard - Arduino Compatible — use interrupt-driven pulse counting for accurate readings at any flow rate
- Durable Body — nylon/plastic construction suitable for cold water applications
🏠 Perfect For
Smart Water Meter
Install inline on your mains water supply. Connect to a D1 Mini running ESPHome. Track daily, weekly, and monthly water consumption in Home Assistant — catch leaks early by monitoring unusual usage.
Pool Flow Monitoring
Mount on the pool pump return line to verify pump flow rate. Alert if flow drops below threshold — indicates a clogged filter, air lock, or failing pump.
Irrigation Metering
Measure exactly how much water each irrigation zone receives. Combine with a smart valve to auto-shutoff after a set volume — no more guessing or overwatering.
Borehole Monitoring
Track borehole pump output and detect declining yield. Set alerts if flow drops below expected levels — early warning of pump issues or dropping water table.
pulse_counter platform in ESPHome. Connect the yellow signal wire to a GPIO pin (e.g. D2/GPIO4 on a D1 Mini). Set the calibration factor based on the sensor's pulse-per-litre rating (typically ~0.2 pulses/mL for DN40). This gives you litres/min and total consumption directly in Home Assistant.🔀 DN40 (1½") vs ¾" — Which Size?
YF-DN40 (this product) — 1½" BSP thread, 5–150 L/min. For mains supply lines, borehole outlets, pool pump returns, and large irrigation. Standard SA municipal supply pipe is typically 20–25mm, so you may need a reducer.
YF-B9 — ¾" BSP thread, 2–50 L/min. For household branch lines, garden taps, individual appliance monitoring (geyser inlet, washing machine), and smaller irrigation zones. More common for typical SA home plumbing.
📋 Technical Specifications
| Product | YF-DN40 Water Flow Sensor |
| Model | YF-DN40 |
| Thread Size | 1½" BSP (DN40) |
| Flow Range | 5–150 L/min |
| Working Voltage | DC 5V |
| Max Water Pressure | 1.75 MPa |
| Output | Hall effect pulse (square wave) |
| Wiring | Red (5V) · Black (GND) · Yellow (Signal) |
| Suitable For | Cold water only |
| Body Material | Nylon / engineering plastic |
| Compatible With | ESP8266 · ESP32 · Arduino · Raspberry Pi · ESPHome · Home Assistant |
🔗 Pair With
D1 Mini
Compact ESP8266 board. Flash ESPHome, connect the flow sensor signal wire to a GPIO — smart water meter in minutes.
View Product →NodeMCU ESP8266
Larger ESP8266 dev board with more GPIOs. Ideal for prototyping flow + pressure + TDS multi-sensor projects.
View Product →❓ Frequently Asked Questions
Does it have a built-in display or WiFi?
pulse_counter sensor.Can I use it with hot water?
Will it fit my SA plumbing?
How accurate is it?
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Know Your Water 💧
Track flow rate, consumption, and leaks with a DIY smart water meter.