Pond and Pool Water Level and Temperature Monitor

Evaporation, leaks and heavy rain change your water level. Mount a JSN-SR04T above the surface pointing down and an ESP32 turns the echo time into centimetres, while a DS18B20 probe tells you if the water is warm enough to swim.

Mission steps

1. Mount the sensor

   Fix the ultrasonic head at least 25 cm above the highest water level, pointing straight down, away from walls.

2. Wire it safely

   The JSN-SR04T runs on 5 V; use a voltage divider (for example 1 kΩ and 2 kΩ) on its echo line before GPIO6. Probe data to GPIO4 with a 4.7 kΩ pull-up.

3. Flash ESPHome

   Use the YAML: the ultrasonic platform measures distance, and a template sensor converts it to water depth.

4. Set the mount height

   Measure from the sensor to the pool or pond floor and put that value in the template.

5. Add alerts

   Notify when the level drops a few centimetres in a day — that often means a leak.

Code

one_wire:
  - platform: gpio
    pin: GPIO4

sensor:
  - platform: dallas_temp
    name: "Water Temperature"
    update_interval: 60s

  - platform: ultrasonic
    id: dist
    name: "Distance to Water"
    trigger_pin: GPIO5
    echo_pin: GPIO6
    update_interval: 60s
    filters:
      - median:
          window_size: 5

  - platform: template
    name: "Water Depth"
    unit_of_measurement: "cm"
    update_interval: 60s
    lambda: |-
      const float MOUNT_M = 1.50;   // sensor height above the floor, in metres
      return (MOUNT_M - id(dist).state) * 100.0;

Tip: test every script on the bench before installing it in a moving machine.

Questions