How to Make an Automatic Water Pump Controller Using Arduino, ESP32 & STM32 – Complete Guide

Are you tired of manually switching your water pump ON and OFF? Do you want to automatically fill your overhead water tank, prevent water overflow, protect your pump from running dry, or monitor water levels directly from your smartphone?

An automatic water pump controller using Arduino, ESP32, or STM32 can help solve these problems.

Using microcontrollers, water level sensors, relay modules, and smart automation technology, you can build a water pump control system that automatically starts the pump when the water level becomes low and stops it when the tank reaches its maximum level.

More advanced systems can also provide IoT water tank monitoring, mobile app control, dry-run protection, pump scheduling, wireless communication, and automatic fault detection.

At ArduinoExpert, we have developed several related water monitoring and pump automation projects, including our Water Tank and Water Pump Automation Using ESP32, which combines a waterproof ultrasonic sensor, ESP32 microcontroller, relay module, and Blynk IoT application.

In this complete guide, you will learn:

• What an automatic water pump controller is and how it works.
• Which components are required to build a water pump automation system.
• How to make a water pump controller using Arduino Uno.
• How to develop an IoT water pump controller using ESP32.
• How to build an STM32-based automatic water level controller.
• How to connect water level sensors and relay control modules.
• How to prevent tank overflow and protect pumps from dry running.
• How to add Wi-Fi, Bluetooth, GSM, and mobile app connectivity.
• How to extend a basic water pump project into a smart monitoring or commercial automation system.

Whether you are developing a simple home water tank controller or a more advanced industrial and agricultural water pumping system, this guide will help you understand the hardware, programming, and design considerations.

1. What Is an Automatic Water Pump Controller?

An automatic water pump controller is an electronic system that monitors water levels and controls the operation of a water pump without requiring continuous manual intervention.

Traditional water pumping systems often depend on someone physically turning the pump ON when the tank becomes empty and switching it OFF when the tank becomes full.

This approach creates several problems:

• Water tank overflow and unnecessary water wastage.
• Unexpected water shortages.
• Unnecessary pump operation.
• Potential pump damage due to dry running.
• Difficulty monitoring underground or overhead tanks.
• Dependence on manual operation.
• Limited visibility into pump faults and operating conditions.

A microcontroller-based water pump automation system addresses these issues by continuously reading sensors and deciding when the pump should operate.

How Does an Automatic Water Pump Controller Work?

A typical automatic water level controller operates according to the following sequence:

1. A water level sensor continuously monitors the level inside the storage tank.
2. The Arduino, ESP32, or STM32 reads the sensor information.
3. When the water level falls below the configured minimum, the controller checks whether water is available at the source.
4. If the required safety conditions are satisfied, the controller activates the pump-control relay or contactor.
5. The pump transfers water into the tank.
6. When the tank reaches its maximum level, the controller switches the pump OFF.
7. If the source tank becomes empty or a fault is detected, the system stops the pump.

For example, a smart controller with continuous level measurement might use these settings:

Tank water level	Automatic pump operation
0–20%	Start pump if source water is available
21–89%	Maintain the current pump state
90–100%	Stop pump
Source tank empty	Stop pump and inhibit operation
Sensor fault detected	Stop pump and generate an alert

This approach uses hysteresis, meaning the pump starts and stops at different water levels.

Hysteresis prevents frequent switching when the water level fluctuates around a single threshold.

For continuous water level monitoring and customized pump control, explore our Smart Water Tank Monitoring System Development Services.

2. Benefits of an Automatic Water Pump Control System

Automatic Water Tank Filling

The controller automatically fills the tank when water is low and stops when the desired level is reached.

Water Overflow Prevention

A properly installed and tested high-level sensor prevents normal pump operation from continuing once the tank reaches its selected maximum level.

For greater reliability, a separate hardwired high-high-level safety cutoff should also be considered.

Water Pump Dry-Run Protection

A source-tank water level switch can prevent pump operation when the supply tank is empty.

For more complete protection, additional flow, pressure, motor-current, or pump-controller feedback may be needed to detect loss of prime, blocked suction, or other no-water conditions.

Reduced Manual Operation

Users no longer need to continuously check tank levels or operate the pump manually.

Remote Water Pump Monitoring

An ESP32-based IoT controller can provide real-time water level information and pump status through Wi-Fi-connected mobile applications.

Flexible Automation

The same technology can be adapted for:

• Home water tanks.
• Underground-to-overhead tank pumping.
• Water storage reservoirs.
• Agricultural irrigation systems.
• Greenhouses and gardens.
• Commercial buildings.
• Industrial water management.
• Solar-powered tubewell systems.

3. Components Required to Make an Automatic Water Pump Controller

The exact components depend on the microcontroller, sensor technology, pump type, and desired automation features.

For a basic demonstration project, the following components are suitable.

Component	Function
Arduino Uno, ESP32 DevKit, or STM32 development board	Main controller
Two float switches	Detect minimum and maximum destination-tank levels
One source-tank float switch	Detect low source-water availability
Compatible relay module or driver	Provide a low-voltage control output
Small low-voltage DC water pump	Demonstration load
Suitable external DC power supply	Power the pump and electronics
Jumper wires and connectors	Electrical connections
Breadboard or prototype PCB	Low-voltage circuit prototyping
Optional waterproof ultrasonic sensor	Continuous water level measurement
Optional LCD/OLED display	Local status display
Optional Wi-Fi/GSM/LoRa interface	Remote monitoring and control

Important: A microcontroller GPIO pin must never power a motor directly. A real AC pump requires appropriately rated motor-control equipment, protective devices, and professional electrical installation. Ordinary hobby relay modules should not be assumed suitable for switching a mains water-pump motor.

Which Water Level Sensor Should You Use?

There are several methods of detecting water levels.

Float Switch Water Level Sensor

A float switch is a mechanical sensor that changes its electrical contact state according to the water level.

Advantages include simple interfacing, low cost, and suitability for fixed low-level or high-level detection.

For a basic automatic water pump controller, float switches are often the easiest starting point.

Ultrasonic Water Level Sensor

An ultrasonic sensor measures the distance between the sensor and the water surface.

Unlike a simple float switch, it can provide continuous water level measurement.

Waterproof ultrasonic sensors such as the JSN-SR04T are useful for many overhead tank monitoring projects, provided their measurement range, blind zone, mounting arrangement, and environmental limitations suit the tank.

We used this type of measurement approach in our ESP32 Water Tank and Pump Automation Project.

Hydrostatic Pressure Sensor

A hydrostatic level sensor estimates the water depth from the pressure produced by the water column.

It can be useful for deep tanks, underground reservoirs, and applications where top-mounted ultrasonic measurement is difficult.

Conductive Water Level Sensor

Conductive probes detect water through electrical conductivity.

They can be used in some basic water level controller designs, although corrosion, deposits, and water conductivity must be considered.

Comparison of Water Level Sensors

Sensor type	Main advantage	Typical application
Float switch	Simple ON/OFF level detection	Basic water pump automation
Ultrasonic sensor	Non-contact continuous level measurement	IoT water tank monitoring
Pressure sensor	Suitable for various tank depths	Underground and industrial tanks
Conductive probe	Economical point-level detection	Basic level indicators
Capacitive sensor	Contact or non-contact sensing, depending on design	Specialized tank monitoring
Radar sensor	Advanced non-contact measurement	Industrial and demanding environments

For this tutorial, we will first use three float switches because they allow the same basic hardware concept and control logic to work with Arduino, ESP32, and STM32.

Later, we will explain how to extend the system using ultrasonic sensors and IoT connectivity.

4. Arduino vs ESP32 vs STM32: Which Is Best for Water Pump Automation?

One of the first design decisions is choosing a suitable microcontroller.

Arduino, ESP32, and STM32 can all control water pumps, but they offer different capabilities.

Feature	Arduino Uno	ESP32	STM32
Beginner-friendly development	Excellent	Very good	Moderate
Digital sensor interfacing	Yes	Yes	Yes
Relay or contactor control output	Yes, with interface hardware	Yes, with interface hardware	Yes, with interface hardware
Built-in Wi-Fi	No	Yes, on common ESP32 boards	Usually requires an external interface
Bluetooth	External module required	Available on many ESP32 variants	Depends on model or external hardware
Operating GPIO logic	Generally 5V on classic Uno	3.3V	Generally 3.3V, with pin-specific exceptions
Real-time control capabilities	Basic	Good	Broad range, depending on MCU
IoT water tank monitoring	Requires additional hardware	Particularly suitable	Possible with connectivity hardware
Custom embedded product development	Possible	Very suitable	Very suitable

When Should You Choose Arduino?

Choose Arduino Uno when you need:

• A beginner-friendly water pump automation project.
• Simple float switch control.
• Basic sensor interfacing.
• A classroom or student demonstration.
• An affordable standalone controller prototype.

When Should You Choose ESP32?

Choose ESP32 when your project requires:

• Wi-Fi-based water pump control.
• Mobile application integration.
• Remote water level monitoring.
• Bluetooth connectivity.
• MQTT or cloud dashboards.
• Smart home or IoT water management.

When Should You Choose STM32?

Choose STM32 when you need:

• A custom embedded water pump controller.
• More advanced peripheral and control requirements.
• Industrial communication integration.
• Structured firmware architecture.
• A production-oriented embedded design.
• Integration with motor-control or monitoring electronics.

An STM32 is not automatically more reliable than Arduino or ESP32. System reliability depends on the complete electrical design, firmware, protection circuitry, sensors, power supply, and testing.

ArduinoExpert offers STM32 Development Services for customized embedded systems, sensor integration, firmware development, and industrial automation applications.

5. Understanding the Automatic Water Pump Controller Circuit

Before programming the microcontroller, we need to understand how the hardware communicates.

Our example uses:

• One float switch at the lower level of the destination tank.
• One float switch at the upper level of the destination tank.
• One source-tank float switch.
• One pump-control relay output.

Basic System Architecture

Destination tank float switches → Microcontroller → Relay driver → Pump-control circuit

At the same time:

Source tank float switch → Microcontroller → Pump protection logic

The microcontroller decides whether the pump should run based on the available sensor information.

The relay interface converts the microcontroller’s low-power control signal into a switching command for suitable external equipment.

For larger motors, the relay typically operates a properly rated contactor or compatible motor-controller input rather than switching the motor power directly.

Sensor Positions

The lower destination-tank sensor should be installed at the minimum water level where pump refilling is required.

The upper destination-tank sensor should be installed at the selected maximum filling level.

The source-tank sensor should be positioned to identify when the water supply has fallen below the minimum permitted operating level.

The exact positions depend on tank dimensions, pump flow rate, suction arrangement, and application requirements.

6. Connecting Water Level Sensors to Arduino, ESP32, and STM32

To make the tutorial consistent, the three float switches will use digital input pins with internal pull-up resistors.

For this example, orient and verify each float switch so that:

Switch submerged in water → contact closed → digital input LOW

Switch not submerged → contact open → digital input HIGH

Some float switches can be physically reversed to change their contact behavior. Always check the actual switching orientation before using the circuit.

Arduino Uno Pin Connections

Component	Arduino Uno pin
Destination tank lower float	D2
Destination tank upper float	D3
Source tank float	D4
Relay control input	D8
Float switch common terminals	GND

ESP32 Pin Connections

The following connections are intended for a common ESP32 DevKit board.

Component	ESP32 pin
Destination tank lower float	GPIO26
Destination tank upper float	GPIO27
Source tank float	GPIO33
Relay control input	GPIO25
Float switch common terminals	GND

ESP32 pins operate at 3.3V logic levels. Use relay modules or driver circuits specifically compatible with 3.3V control signals.

Do not connect 5V sensor outputs directly to ordinary ESP32 GPIO inputs.

STM32 Pin Connections

For this example, we will use an STM32F103C8T6 Blue Pill development board.

Component	STM32 pin
Destination tank lower float	PB12
Destination tank upper float	PB13
Source tank float	PB14
Relay control input	PB15
Float switch common terminals	GND

Use a suitable 3.3V-compatible relay driver and verify the actual pin mappings for your STM32 board.

Electrical safety: These tables describe only the low-voltage sensor and control connections. They do not describe mains motor wiring. Do not connect AC mains to a breadboard or route pump motor current through the microcontroller. Use a separate, appropriately protected motor power circuit installed by a qualified electrician.

7. Automatic Water Pump Controller Arduino Code

The following Arduino-style program demonstrates a common control algorithm that can be compiled for:

• Arduino Uno.
• ESP32 DevKit.
• STM32F103 Blue Pill using the STM32 Arduino core.

The program automatically selects the GPIO pins according to the selected microcontroller platform.

Features of the Example Code

The program includes:

• Automatic pump ON/OFF control.
• Lower and upper water-level detection.
• Source-tank low-water cutoff.
• Basic inconsistent-sensor-state detection.
• Maximum pump runtime protection.
• Automatic filling between two defined thresholds.

Note: This is an educational prototype program for a low-voltage test setup. It is not a complete, independently validated pump safety controller. Real installations also require input debouncing, protection against sensor wiring faults, appropriately designed startup states, electrical interlocks, and independent safety devices.

Common Arduino, ESP32, and STM32 Program

// Automatic Water Pump Controller
// Arduino Uno / ESP32 / STM32
// ArduinoExpert.com
//
// Float switch convention:
// Wet = switch closed to GND = LOW
//
// Relay module convention:
// Active LOW = relay ON
//
// Educational low-voltage prototype only.

#if defined(ARDUINO_ARCH_ESP32)

const int TANK_LOW_PIN = 26;
const int TANK_HIGH_PIN = 27;
const int SOURCE_PIN = 33;
const int RELAY_PIN = 25;

#elif defined(ARDUINO_ARCH_STM32)

const int TANK_LOW_PIN = PB12;
const int TANK_HIGH_PIN = PB13;
const int SOURCE_PIN = PB14;
const int RELAY_PIN = PB15;

#else

// Arduino Uno
const int TANK_LOW_PIN = 2;
const int TANK_HIGH_PIN = 3;
const int SOURCE_PIN = 4;
const int RELAY_PIN = 8;

#endif

const int RELAY_ON = LOW;
const int RELAY_OFF = HIGH;

// Example maximum runtime: 15 minutes.
// Adjust after measuring real tank filling time.
const unsigned long MAX_RUN_MS =
    15UL * 60UL * 1000UL;

bool pumpRunning = false;
bool faultLatched = false;

unsigned long pumpStartMs = 0;

bool isWet(int pin) {
  return digitalRead(pin) == LOW;
}

void setPump(bool on) {
  pumpRunning = on;

  if (on) {
    pumpStartMs = millis();
  }

  digitalWrite(
    RELAY_PIN,
    on ? RELAY_ON : RELAY_OFF
  );
}

void setup() {

  // Set the relay output to its inactive state.
  digitalWrite(RELAY_PIN, RELAY_OFF);
  pinMode(RELAY_PIN, OUTPUT);
  setPump(false);

  pinMode(TANK_LOW_PIN, INPUT_PULLUP);
  pinMode(TANK_HIGH_PIN, INPUT_PULLUP);
  pinMode(SOURCE_PIN, INPUT_PULLUP);
}

void loop() {

  bool tankLowWet = isWet(TANK_LOW_PIN);
  bool tankHighWet = isWet(TANK_HIGH_PIN);
  bool sourceWet = isWet(SOURCE_PIN);

  // A high sensor reporting water while the
  // lower sensor is dry is inconsistent.
  if (tankHighWet && !tankLowWet) {
    faultLatched = true;
  }

  // Stop if the pump has operated too long.
  if (pumpRunning &&
      millis() - pumpStartMs >= MAX_RUN_MS) {
    faultLatched = true;
  }

  // Stop when the tank is full, the water
  // source is empty, or a fault occurs.
  if (pumpRunning &&
      (tankHighWet ||
       !sourceWet ||
       faultLatched)) {

    setPump(false);
  }

  // Start only when the destination tank
  // is below its lower threshold and
  // source water is available.
  if (!pumpRunning &&
      !faultLatched &&
      !tankLowWet &&
      !tankHighWet &&
      sourceWet) {

    setPump(true);
  }

  delay(200);
}

How the Code Works

The program reads three input signals:

1. TANK_LOW_PIN checks whether water has reached the lower tank sensor.
2. TANK_HIGH_PIN checks whether water has reached the upper tank sensor.
3. SOURCE_PIN verifies that water is available in the source tank.

When both destination-tank float switches are dry, and the source tank has sufficient water, the controller turns the pump ON.

Once the pump starts, it continues filling the tank until the upper sensor becomes wet.

If source water becomes unavailable, the pump stops.

If the upper sensor detects water while the lower sensor reports dry, the program considers this an inconsistent sensor condition and activates a fault latch.

The maximum runtime limit provides an additional software cutoff if the destination tank fails to reach its upper sensor within the configured time.

A latched fault in this demonstration requires the cause to be investigated and the controller reset.

Important limitation: A disconnected upper float-switch wire can incorrectly appear dry under this wiring convention. Therefore, this example cannot guarantee overflow prevention in the presence of every wiring or sensor fault. A real installation should include an independently wired high-level cutoff that de-energizes the pump-control equipment.

Also, a source-tank float switch alone cannot detect all causes of pump dry running, such as a blocked suction pipe or failed prime.

8. How to Make an Automatic Water Pump Controller Using Arduino Uno

Arduino Uno is an excellent starting point for students, hobbyists, and beginners learning microcontroller-based automation.

Step 1: Prepare the Components

You will need:

• Arduino Uno.
• Three appropriately configured float switches.
• An Arduino-compatible relay driver module.
• A small low-voltage demonstration pump.
• Separate suitable power supplies.
• Jumper wires and a prototype board.

Step 2: Connect the Water Level Sensors

Connect the lower tank sensor to Arduino digital pin D2 and the upper tank sensor to D3.

Connect the source-tank float switch to D4.

Connect the other terminal of each switch to Arduino GND.

The program uses internal pull-up resistors, so an open switch reads HIGH and a closed switch reads LOW.

Step 3: Connect the Relay Module

Connect the relay module’s control input to Arduino D8.

Provide the relay module with the power supply and interface connections required by its manufacturer.

Use only a suitably rated low-voltage demonstration load during initial testing.

Step 4: Install Arduino IDE

Download the Arduino IDE from the official Arduino website.

Connect the Arduino Uno to your computer using a USB cable.

Select the appropriate board and COM port.

Step 5: Upload the Program

Open a new sketch in Arduino IDE.

Copy the common water pump controller program provided above.

Select Arduino Uno as the target board, verify the sketch, and upload it.

Step 6: Test the Automation

First, disconnect the physical pump load.

Test the sensor states and relay command using a suitable indicator or test instrument.

Verify these conditions:

• Destination tank low and source tank available: pump command ON.
• Destination tank reaches the upper level: pump command OFF.
• Source water becomes unavailable: pump command OFF.
• Contradictory float switch readings: fault condition.
• Maximum runtime exceeded: pump command OFF.

After confirming that the control logic works, test with a properly connected low-voltage DC pump.

Extending Arduino Pump Automation with a Touchscreen

A basic Arduino water pump controller can be expanded using a touchscreen interface, scheduling functions, and multiple output channels.

ArduinoExpert has developed an Irrigation Scheduling and Water Pumps Control System Using Touch LCD and Arduino Uno.

This project uses a Nextion touchscreen interface to manage irrigation schedules and control water pumps.

Such an approach is particularly useful when an operator requires local control without depending on internet connectivity.

9. How to Make an IoT Water Pump Controller Using ESP32

The ESP32 is an attractive choice for building a Wi-Fi water pump controller with mobile app monitoring.

Unlike a classic Arduino Uno, many ESP32 development boards include built-in Wi-Fi and Bluetooth capabilities.

This makes them suitable for smart homes, connected water tanks, and remote monitoring applications.

Step 1: Select an ESP32 Development Board

A common ESP32 DevKit can be used to build a water tank monitoring and pump control prototype.

For this guide, use the ESP32 GPIO connections listed earlier.

Step 2: Connect the Sensors and Relay Interface

Connect:

• Lower tank float switch to GPIO26.
• Upper tank float switch to GPIO27.
• Source-tank float switch to GPIO33.
• Relay interface to GPIO25.

Confirm that the relay driver accepts 3.3V control signals and cannot unintentionally activate the motor during startup or reset.

Step 3: Install ESP32 Board Support

Open Arduino IDE and install the appropriate ESP32 board package using Boards Manager.

Select the exact ESP32 development board or a compatible board profile.

Step 4: Upload the Automation Program

Upload the same example program used for Arduino Uno.

The ESP32-specific GPIO assignments will be selected automatically.

At this stage, the example operates locally without Wi-Fi or cloud connectivity.

This is intentional: critical water-level control should not depend on the internet.

Step 5: Add IoT Water Tank Monitoring

Once the basic automation logic is working, you can integrate the ESP32 with:

• Blynk IoT.
• MQTT dashboards.
• Firebase.
• ThingsBoard.
• A custom web application.
• A custom smartphone application.

An IoT water pump monitoring dashboard can display:

• Current tank level.
• Pump ON/OFF status.
• Automatic or manual operating mode.
• Low-water warnings.
• Water tank full alerts.
• Pump runtime.
• Sensor fault notifications.

ESP32 Water Pump Control with Blynk App

For a dedicated implementation of smartphone-based water pump switching, explore our IoT Water Pump Control System Using ESP32 and Blynk.

This project demonstrates remote pump control through an ESP32 and Blynk application, including electronics development, firmware, and enclosure design.

For an integrated water level monitoring example, see our Water Tank and Pump Automation Using ESP32, Ultrasonic Sensor, and Blynk.

Bluetooth Water Pump Control Using ESP32

Not every pump controller needs internet connectivity.

If the controller is installed nearby, Bluetooth may provide a convenient method of controlling it from a smartphone.

ArduinoExpert has also developed a Bluetooth Pump Control System Using ESP32.

Bluetooth is suitable for local operation, configuration, or monitoring within the supported communication range.

For remote access from another city or country, an internet-connected or cellular-based solution is generally more appropriate.

10. How to Make an Automatic Water Pump Controller Using STM32

STM32 microcontrollers are widely used in embedded electronic products and industrial control applications.

They provide a broad selection of microcontroller families, peripherals, timers, communication interfaces, and development tools.

An STM32-based automatic water level controller can be suitable when the application requires a custom embedded hardware design or additional monitoring and control functionality.

Step 1: Choose the STM32 Board

For a learning prototype, an STM32F103C8T6 Blue Pill board can be used.

The board provides digital GPIO connections suitable for reading float switches and controlling an external relay driver.

For more advanced applications, developers may select other STM32 boards according to memory, peripheral, operating temperature, communication, and performance requirements.

Step 2: Connect Sensors and Control Output

For the example program:

• PB12 reads the lower tank float.
• PB13 reads the upper tank float.
• PB14 reads the source-tank float.
• PB15 controls the relay interface.

All sensor interfaces and output drivers must be electrically compatible with the selected STM32 board.

Step 3: Configure the STM32 Development Environment

There are two common programming approaches.

Option 1: Arduino IDE with STM32 Core

This approach is convenient when transferring an Arduino-style automation project to supported STM32 hardware.

Install the STM32 MCU board package using the official STM32duino setup instructions.

Select the correct STM32 board variant and upload method.

Option 2: STM32CubeIDE

For applications requiring STM32 HAL libraries, interrupts, timers, communication peripherals, structured debugging, or more advanced firmware design, STM32CubeIDE is another option.

The example sketch in this tutorial is written for the Arduino-compatible STM32 core. It is not a direct STM32 HAL or STM32CubeIDE project.

Step 4: Upload the Program

Select the appropriate board configuration in Arduino IDE.

Use the common program provided earlier.

The STM32 pin definitions will be selected automatically.

Depending on the development board and configuration, you may need a supported USB bootloader or an ST-Link programming/debugging adapter.

Step 5: Test the STM32 Controller

Test the three sensor inputs and relay-control output under controlled low-voltage conditions.

Verify the automatic filling sequence, source-water cutoff, inconsistent-sensor fault behavior, and runtime protection.

Advanced STM32 Water Pump Control

An STM32-based controller can be extended with additional features such as:

• Multiple pump control.
• Pressure sensor monitoring.
• Flow meter integration.
• Automatic pump alternation.
• RS485/Modbus communication.
• External industrial motor-control interfaces.
• Local HMI displays.
• Data logging and alarms.
• Watchdog supervision.
• Sensor-fault detection.
• Communication with PLC or SCADA systems.

For professional embedded development, ArduinoExpert provides Custom STM32 Firmware and Embedded Systems Development Services.

11. How to Measure Water Tank Level Using an Ultrasonic Sensor

Float switches are suitable for identifying predefined water levels, but they do not provide continuous information about how full the tank is.

For a smart water tank monitoring system, an ultrasonic sensor can be used to estimate the water level in centimeters or as a percentage.

Working Principle

An ultrasonic sensor sends an acoustic pulse toward the water surface.

The sound reflects from the surface and returns to the sensor.

The sensor uses the pulse travel time to estimate the distance to the water.

The basic distance formula is:

Distance = (Speed of sound × Echo time) / 2

The division by two accounts for the sound traveling to the water surface and returning.

Calculating Water Level Percentage

For a top-mounted sensor, two calibrated measurements are especially useful:

• Empty distance: Distance measured when the tank is empty.
• Full distance: Distance measured when the tank reaches its selected maximum level.

The water level percentage can be estimated using:

Water Level (%) = [(Empty Distance − Measured Distance) / (Empty Distance − Full Distance)] × 100

For example:

• Empty distance = 90 cm.
• Full distance = 10 cm.
• Current measured distance = 50 cm.

Water Level = [(90 − 50) / (90 − 10)] × 100

Water Level = 50%

The calculated value should be limited to the 0–100% range and invalid sensor readings should be rejected.

This percentage represents calibrated water depth. In tanks with irregular geometry, it may not be the same as the percentage of total water volume.

Ultrasonic Sensor Integration with ESP32

A typical smart ultrasonic water-level monitoring system contains:

1. ESP32 microcontroller.
2. Waterproof ultrasonic sensor.
3. Relay or motor-control interface.
4. Appropriate DC power supplies.
5. Wi-Fi connectivity.
6. Optional mobile application or local display.
7. Independent safety sensors.

If the ultrasonic sensor produces a 5V echo signal, a suitable level shifter or voltage divider is required before connecting it to an ESP32 or a non-5V-tolerant STM32 input.

Practical tip: Check the ultrasonic sensor’s minimum measurable distance, beam angle, condensation exposure, turbulence, and installation position. A sensor with a large blind zone may not be suitable for a shallow tank.

Our ESP32 Water Tank Automation Project provides a related practical example of ultrasonic water level monitoring.

12. IoT Water Pump Automation Using NodeMCU ESP8266

Although Arduino, ESP32, and STM32 are the primary platforms discussed in this guide, NodeMCU ESP8266 is another useful option.

NodeMCU is popular for low-cost Wi-Fi automation projects.

A NodeMCU-based water pump monitoring system can connect sensors and a relay interface while sending information to a cloud application.

ArduinoExpert developed an IoT Water Pump Tank Automation and Temperature Monitoring System Using NodeMCU ESP8266.

The project integrates:

• NodeMCU ESP8266.
• Ultrasonic water level measurement.
• Waterproof DS18B20 temperature sensor.
• Relay-controlled water pump operation.
• I2C LCD display.
• Blynk IoT mobile application.
• Automatic and manual control modes.

It demonstrates how a relatively simple water pump controller can be expanded to include additional sensing and user interface features.

For projects requiring continuous water temperature monitoring alongside tank level automation, this type of architecture can be particularly useful.

13. How to Control a Water Pump Using a Mobile Phone

A smart water pump controller can be designed to work with different communication technologies.

The most appropriate technology depends on the application, distance, connectivity, cost, and reliability requirements.

Wi-Fi Water Pump Control

Wi-Fi is suitable for homes, buildings, laboratories, and facilities where wireless network coverage is available.

An ESP32 can communicate with a smartphone application or IoT dashboard.

With an appropriate cloud or remote-access system, authorized users can monitor or control their water pumps from different locations.

Bluetooth Water Pump Control

Bluetooth is useful for local smartphone control when internet connectivity is unnecessary.

It is well suited for nearby configuration, testing, and local pump switching.

GSM and SMS Water Pump Control

For remote agricultural locations, GSM or other suitable cellular technologies may be preferable to Wi-Fi.

An SMS-enabled controller can receive commands from an authorized mobile number and operate a pump through appropriate motor-control equipment.

This approach does not require fixed broadband internet at the pump location, although compatible cellular network and SMS service are necessary.

Our Tubewell Water Pump Control Through SMS or Smartphone App project demonstrates a related remote-control concept.

For a more detailed explanation, read our guide on How to Control a Solar Tubewell Water Pump by SMS Without Internet.

LoRa Water Pump Monitoring

LoRa can be useful for communicating sensor readings across long distances between tanks, pumping stations, agricultural fields, and monitoring points.

However, LoRa alone does not provide a mobile internet connection. A gateway or another communication link is required when internet-based monitoring is needed.

Comparing Water Pump Communication Technologies

Technology	Typical use	Main consideration
Wi-Fi	Home and building monitoring	Requires network coverage
Bluetooth	Nearby smartphone control	Limited operating range
GSM/SMS	Remote pumps and farms	Requires compatible cellular service
4G/Cellular IoT	Remote dashboards and alerts	Data plan and network coverage
LoRa	Long-distance sensor networks	Gateway and network design
RS485/Modbus	Industrial pumps and VFDs	Wired device compatibility

For applications requiring custom phone interfaces, ArduinoExpert also offers Mobile and Web App Development Services.

14. Automatic Water Pump Control with Dry-Run and Overflow Protection

One of the most important parts of a reliable water pump controller is protecting the equipment.

A system that can turn a pump ON and OFF is not necessarily a complete pump protection system.

Water Tank Overflow Protection

An upper-level sensor normally tells the controller when the destination tank is full.

The firmware then switches the pump OFF.

However, sensor failure, disconnected wiring, software problems, or a welded switching contact could prevent normal shutdown.

A more robust design can use:

• Primary water level sensing.
• Independent high-high-level float switch.
• Hardwired safety shutdown.
• Maximum pump runtime limit.
• Fault indication.
• Properly rated motor-control equipment.

Dry-Run Protection

A water pump may run without sufficient water because of:

• An empty source tank.
• Blocked suction piping.
• Loss of priming.
• Air entering the suction line.
• Inadequate source flow.
• Other hydraulic or equipment faults.

A source-tank float switch helps prevent operation when the available water level is too low.

For additional protection, the system may need:

• Flow monitoring.
• Pressure sensing.
• Motor current monitoring.
• Underload detection.
• VFD-based dry-run protection.
• Fault feedback from the pump controller.

Pump Runtime Protection

A runtime limit provides a useful additional safety feature.

For example, if a pump normally fills a tank within ten minutes, an unexpected increase in filling time could indicate a problem.

The controller may be programmed to stop the pump after a configured maximum runtime.

The timeout should be based on measured system performance rather than an arbitrary value.

Safe Manual Control

If a manual ON/OFF function is added through a touchscreen, mobile application, or local button, essential safety interlocks should remain active.

Manual commands must not bypass low-source-water protection, emergency stops, motor overload protection, or other required safety functions.

15. Troubleshooting an Automatic Water Pump Controller

During development, you may encounter several common issues.

Problem	Possible reason	Recommended check
Pump command does not turn ON	Incorrect float orientation or relay polarity	Verify sensor states and relay logic
Pump does not stop at the upper level	Upper sensor or wiring fault	Test upper-level input and independent cutoff
Pump switches frequently	Sensor chatter or unstable water level	Add filtering, debounce and hysteresis
ESP32 resets when relay activates	Electrical noise or inadequate power supply	Review supply isolation, grounding and relay driver
Incorrect ultrasonic readings	Sensor blind zone, condensation or mounting	Check installation and sensor validity
Remote app does not connect	Wi-Fi or cloud connection problem	Check network configuration
Relay works but pump does not	External control or motor circuit issue	Have qualified personnel inspect motor equipment
Pump stops before tank is full	Maximum runtime too short	Measure actual filling time and inspect flow

For permanent installations, additional testing should cover power failures, reconnection behavior, sensor disconnections, electrical noise, communication failures, and long-term outdoor operation.

16. Applications of Smart Water Pump Automation Systems

Home Water Tank Automation

A smart controller can automatically transfer water from an underground tank to an overhead storage tank.

This reduces the need for residents to manually monitor tank levels.

Apartment and Commercial Building Water Management

Larger buildings may require monitoring of multiple water tanks, transfer pumps, and booster pumps.

A centralized monitoring dashboard can display tank levels, pump status, alarms, and maintenance information.

Agricultural Irrigation

A water pump automation system can be combined with soil moisture sensors, irrigation schedules, and remotely controlled valves.

ArduinoExpert provides Smart Irrigation System Development Services for agricultural farms, gardens, greenhouses, and other irrigation applications.

Solar Tubewell Water Pump Control

Solar-powered water pumping systems may use VFDs or dedicated pump controllers.

Remote operation can be provided using compatible control inputs or RS485/Modbus communication.

ArduinoExpert has developed the AabNex SMS Solar Tubewell VFD Controller, which supports SMS-based remote operation and monitoring for compatible VFD systems.

This is an example of moving beyond a basic relay project to more advanced pump-control integration.

Industrial Water Management

Industrial systems may require:

• Multiple water tanks.
• High and low-level alarms.
• Continuous liquid-level monitoring.
• Pump alternation.
• Flow and pressure monitoring.
• Motor fault feedback.
• PLC or SCADA integration.
• Data logging.
• Remote supervision.

Such systems should be engineered according to the applicable electrical, safety, and operational requirements.

17. How to Convert a DIY Water Pump Controller into a Commercial Product

A breadboard-based water pump controller is useful for learning and verifying the basic control concept.

However, developing a commercial water tank monitoring product requires additional engineering.

Custom PCB Design

A custom PCB can integrate the microcontroller, sensor interfaces, power regulation, communication circuitry, and pump-control output stages.

Reliable Power Supply Design

The system should tolerate expected voltage fluctuations and electrical noise while maintaining defined and safe operating states.

Enclosure Design

Depending on the installation, the enclosure may require protection against dust, splashes, humidity, sunlight, and environmental exposure.

Firmware Development

Commercial firmware may need:

• Sensor filtering and calibration.
• Watchdog supervision.
• Fault logging.
• Communication recovery.
• Secure device configuration.
• Controlled firmware updates.
• Defined recovery after power loss.
• Safe relay and contactor startup behavior.

Mobile App and Cloud Integration

A commercial smart water tank monitoring product may provide:

• Multiple user accounts.
• Tank level graphs.
• Push notifications.
• Device status.
• Pump operating history.
• Remote configuration.
• Multi-site monitoring.
• Secure communication.

Testing and Validation

The complete controller should be tested under realistic operating conditions, including fault scenarios and loss of communication.

At ArduinoExpert, we provide Custom Electronics and IoT Project Development Services covering hardware design, embedded programming, prototyping, and product development.

19. Need a Custom Automatic Water Pump Controller or Smart Water Tank Monitoring System?

Every water pump automation project has different requirements.

A homeowner may need a simple automatic overhead tank controller, while a farmer may require GSM-based tubewell control. A commercial building may need several tank sensors, multiple pumps, alarms, and centralized monitoring.

At ArduinoExpert, we develop customized electronics, IoT, and embedded automation solutions.

Our services include:

• Arduino-based water pump controller development.
• ESP32 Wi-Fi water pump monitoring systems.
• STM32 embedded firmware development.
• Automatic water level controller design.
• Smart underground and overhead tank monitoring.
• IoT dashboards and mobile applications.
• Pump scheduling and irrigation automation.
• GSM, Bluetooth, Wi-Fi, and LoRa connectivity.
• PCB design and embedded product development.
• Prototype development and testing.

If you want to develop your own system, explore our Smart Water Tank Level Monitoring and Pump Automation Development Services.

Conclusion

Building an automatic water pump controller using Arduino, ESP32, or STM32 is a practical way to learn embedded electronics while developing a useful water management system.

A basic design requires a microcontroller, water level sensors, a suitable relay-control interface, and a properly protected pump circuit.

For beginners, Arduino Uno provides a straightforward introduction to automatic water level control.

For smart home and IoT applications, ESP32 offers built-in wireless connectivity and convenient integration with mobile monitoring platforms.

For advanced custom embedded systems, STM32 provides a broad platform for developing specialized monitoring and automation solutions.

The most important engineering consideration is not simply turning the pump ON and OFF. A reliable system should also account for tank overflow, low source-water conditions, sensor failures, motor protection, electrical safety, and safe operation during communication interruptions.

By combining thoughtful hardware design, reliable embedded programming, and appropriate protection systems, you can develop an automatic water pump controller suitable for your intended application.

For more practical embedded electronics and automation projects, visit ArduinoExpert.com.