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The original was posted on /r/homeassistant by /u/ifight4theusername on 2025-05-17 01:23:16+00:00.
This took me hours of searching around to figure out, even though I've seen dozens of similar threads where people were looking to do this. So here it is, all the pieces you need in one place to make this work. Also, a little background on pressure and flow in case you don't know. With all of your faucets closed, no water flowing, you're basically going to have the exact same pressure everywhere. It isn't until you have flow that a pressure differential will form. The bigger the flow, the higher the pressure drop across the restriction (your filter). This drop will gradually get bigger and bigger as the filter gets clogged. There are a lot of factors here, but my system with new filters is around 2.5 psi drop with the bath tub on full blast (not shower head).
- Hardware:
- ESP32 (or whatever ESPHome device you want that is I2C capable)
- ADS1115 (I ordered a few off of amazon)
- Pressure sensor (I ordered 2 Autex 150psi sensors off of Amazon, mainly because they were cheap. They take 5V instead of the 3.3V the ESP is happy with, so the ADS1115 provides a 5V capable reading, plus a lot better ADC than the one in the ESP)
- Whatever plumbing fittings you need to attach a sensor before and after your filter setup (the sensors I used are 1/8" NPT)
- Some sort of breadboard and wiring to connect everything. I highly recommend soldering everything for the final product and not using the solderless breadboards. I know from past projects those can do very weird things when you have radio signals near them and/or doing things at frequencies higher than 1Hz. I did prototype on a solderless breadboard though at 1Hz sample rate.
- My "final" product is a soldered protoboard, with all of the wiring covered in hot glue, wrapped in layers of electrical tape. Nothing but the finest workmanship
- A USB power supply (mine is USB C, 2A capable but this is super overkill for this circuit)
solderless breadboard prototype
"Conformal coating"
Crawl space ready hardware
- Software:
- I'm not going to show you how to flash ESPHome, there are plenty of tutorials out there. Just get your ESP device talking on ESPHome with your HomeAssistant instance. I named mine "ESP_Water_Pressure" if you want to copy that so you can just copy pasta my code
Step 1: There are 4 wires to connect from your ESP to your ADS1115. Look at the pinout sheets for both of your devices, connect the 4 wires below to each component:
ESP -> ADS1115
5V -> 5V (VDD)
GND -> GND
SCL -> SCL
SDA -> SDA
Step 2: On the ADS1115, I wired the pre-filter sensor to A0, and the post filter sensor to A1. Follow that order if you want to copy pasta my code. The sensors have three wires, one 5V, one ground, and one signal. The signal wire goes to A0 or A1, then connect the 5V and ground wires to the power and ground from your ESP.
Step 3: Here's the code for your ESPHome device. Read through the comments for explanations or things you should change
#Use your board populated values except the friendly name
esphome:
name: esphome-web-4f1d78
friendly_name: ESP_Water_Pressure
min_version: 2024.11.0
name_add_mac_suffix: false
#Use your board populated values
esp32:
board: esp32dev
framework:
type: esp-idf
# Enable logging
logger:
# Enable Home Assistant API
api:
# Allow Over-The-Air updates
ota:
- platform: esphome
#Change these values if you are not using the secret file, if you are make sure the names match
wifi:
ssid: !secret wifi_ssid
password: !secret wifi_password
# Make sure you change the GPIO pins to match the ESP board you are using
i2c:
sda: GPIO21
scl: GPIO22
scan: true
id: bus_a
#Config for the ADS1115, default address (not using multiple ADS1115s)
ads1115:
- address: 0x48
sensor:
#First sensor, pre filter
- platform: ads1115
#Choose the pin you want to use for the first sensor
multiplexer: 'A0_GND'
#This is the default gain, idk why, it works
gain: 6.144
name: "Pre-filter Water Pressure"
#Read at 100Hz
update_interval: 0.01s
filters:
#Take 100 samples, average them together, then report every second. I had a lot of noise just using 1 or 10Hz.
- median:
window_size: 100
send_every: 100
send_first_at: 1
#Change this calibration if your sensor data is different, left side is voltage, right is PSI
- calibrate_linear:
method: exact
datapoints:
- 0.5 -> 0.0
- 2.5 -> 75.0
- 4.5 -> 150.0
unit_of_measurement: "PSI"
#Only displays 2 decimals on dashboard but doesn't change reported value
accuracy_decimals: 2
#This shows a gauge on the dash, nice to have
device_class: pressure
#Second sensor, same as the first except the name and multiplexer pin
- platform: ads1115
multiplexer: 'A1_GND'
gain: 6.144
name: "Post-filter Water Pressure"
update_interval: 0.01s
filters:
- median:
window_size: 100
send_every: 100
send_first_at: 1
- calibrate_linear:
method: exact
datapoints:
- 0.5 -> 0.0
- 2.5 -> 75.0
- 4.5 -> 150.0
unit_of_measurement: "PSI"
accuracy_decimals: 2
device_class: pressure
#Use your board populated values except the friendly name
esphome:
name: esphome-web-4f1d78
friendly_name: ESP_Water_Pressure
min_version: 2024.11.0
name_add_mac_suffix: false
#Use your board populated values
esp32:
board: esp32dev
framework:
type: esp-idf
# Enable logging
logger:
# Enable Home Assistant API
api:
# Allow Over-The-Air updates
ota:
- platform: esphome
#Change these values if you are not using the secret file, if you are make sure the names match
wifi:
ssid: !secret wifi_ssid
password: !secret wifi_password
# Make sure you change the GPIO pins to match the ESP board you are using
i2c:
sda: GPIO21
scl: GPIO22
scan: true
id: bus_a
#Config for the ADS1115, default address (not using multiple ADS1115s)
ads1115:
- address: 0x48
sensor:
#First sensor, pre filter
- platform: ads1115
#Choose the pin you want to use for the first sensor
multiplexer: 'A0_GND'
#This is the default gain, idk why, it works
gain: 6.144
name: "Pre-filter Water Pressure"
#Read at 100Hz
update_interval: 0.01s
filters:
#Take 100 samples, average them together, then report every second. I had a lot of noise just using 1 or 10Hz.
- median:
window_size: 100
send_every: 100
send_first_at: 1
#Change this calibration if your sensor data is different, left side is voltage, right is PSI
- calibrate_linear:
method: exact
datapoints:
- 0.5 -> 0.0
- 2.5 -> 75.0
- 4.5 -> 150.0
unit_of_measurement: "PSI"
#Only displays 2 decimals on dashboard but doesn't change reported value
accuracy_decimals: 2
#This shows a gauge on the dash, nice to have
device_class: pressure
#Second sensor, same as the first except the name and multiplexer pin
- platform: ads1115
multiplexer: 'A1_GND'
gain: 6.144
name: "Post-filter Water Pressure"
update_interval: 0.01s
filters:
- median:
window_size: 100
send_every: 100
send_first_at: 1
- calibrate_linear:
method: exact
datapoints:
- 0.5 -> 0.0
- 2.5 -> 75.0
- 4.5 -> 150.0
unit_of_measurement: "PSI"
accuracy_decimals: 2
device_class: pressure
Now you should have sensor data you can add to your dashboard and track... except wouldn't it be way easier to just subtract the values and set an alert when the pressure drop hits a certain PSI? Great, let's do that with a helper. Oh wait, it's 2025 and you CAN'T SUBTRACT TWO VALUES WITH A HELPER?!!?!?!
Fine, let's learn how to make a template sensor.
Step 4: Subtraction is hard. We have to use some YAML to do it. In Home Assistant, go to Settings -> Devices & Services -> Helpers tab -> Create Helper -> Template -> Template a Sensor. If you copied all of my names directly, you can just paste this into the "State template" but make sure you get the name of your device correct.
{{ states('sensor.esphome_web_4f1d78_pre_filter_water_pressure') | float(0) - states('sensor.esphome_web_4f1d78_post_filter_water_pressure') | float(0) }}
Choose psi for unit of measurement, pressure for Device class, measurement for state class, and choose the name of your ESP device for the Device. Your config should look like this:
https://preview.redd.it/y5ht1c9zt81f1.png?width=574&format=png&auto=webp&s=25d19a39a3d381e9605e3fcda72caf531d09da7a
Now you notice that we have way too many decimals... the easiest way I found to "fix" this is to just submit the template, then in your list of helpers, click the options on the template sensor we just made, go to Settings, then in the fourth dropdown box, change the display precision and hit update.
Step 5: slap ...
Content cut off. Read original on https://old.reddit.com/r/homeassistant/comments/1koh7ua/tutorial_esphome_dual_water_pressure_sensors_with/
