Watermain Adaptive Threshold Implementation

• This project starts with Yang's project at https://github.com/heyitsyang/Whole-House-Water-Leak-Controller .

  • Optional adaptations:
    • Buck converter is replaced by dedicated 5v usb supply wall wart for ESP8266.
    • Standard enclosure is substituted for custom 3D printed electronics enclosure.

• Observations

  • Typical 24 hour pressure profile:

  

  • Water pressure varies several psi during the course of a day.
  • Water pressure spikes when water heater is active.
  • Water pressure recovers slowly after demand if there is a pressure regulator.
  • Water flow may not be detected by a static threshhold for slower flow rates or during periods of higher pressure.

How small a leak can we detect without using an impeller?

• Water flow duration was measured under various conditions (flush, shower, laundry, dishes, etc.)
  • An adaptive threshhold was devised to close the main valve 10 minutes after detecting water flow.
  • Motion detected in the bathrooms or kitchen cause a 20 minute grace period (for showers, proof of consciousness, etc.).
  • Leak vol = leak rate x flow detection time + 10 min x leak rate + water residue after valve closes (approx 20 fl oz = 625 ml)
  • 75 ml/min flow is detected in 80 seconds. Total leak = 75(80/60) + 10(75) + 625 = 1475 ml (=6 cups).
    • 40 ml/min flow is detected in 6 minutes. Total leak = 6(40) +10(40) + 625 = 1265 ml (=5 cups).
    • 24 ml/min flow (22 drips/10 sec) is detected in 11 minutes. Total leak = 11(24) + 10(24) + 625 = 1129 ml (<5 cups).
  • Wide open faucet 5.3 liter/min flow would take 10 minutes to shut down. Leak = 10(5.3)+.625 = 54 liters (14 gal).
    • Therefore use moisture sensors to close valve immediately for larger volumes.

Static pressure test results:

• Typical nightly results range betwwen -.03 and -.15 psi at my house.

• Pressure decrease is greater (-. 38 psi +-) if the test is run soon after the water heater has been activated and the pressure tank has peaked and is on the downswing.

• A 24 ml/min leak causes a 3.44 psi drop during the nightly static pressure test under normal conditions.

Adaptive Threshhold Theory of Operation

• The adaptive threshhold is based on a "leaky peak detector".

  • Leaky peak - If pressure (P) rises above the peak value, the calculated peak pressure is set equal P.

    • The peak pressure stays constant for the next 10 minutes unless P exceeds it before then.
    • After 10 minutes, the peak is reduced .25 psi if it doesn't go less than P.
    • If P rate of decrease exceeds .25psi/10 min, the calculated peak pressure decreases at a slower rate. Hence, the term leaky peak.

  • Threshhold (T) - The threshhold that defines flow is set at 1 psi below the most recent calculated leaky peak pressure.

  • Flow - When P goes below the threshhold, the 10 minute flow timer begins. After 10 minutes, the valve is closed.

  • Motion Sensors reset the flow timer when motion is detected.

  • There is a similar mechanism to determine the threshhold when the flow stops and the pressure rises again.

  • Examples:

    • The peak and threshhold (T) are recalculated each time the pressure increases above the prior peak.

      

    • The following plot shows the pressure decreasing at a rate of .125 psi/10 min; the peak is reduced .25 psi / 10 min until the two meet.

    • The plots above and below demonstrate an example of the threshold tracking the normal ebb and flow of psi without tripping the flow threshld.

      

    • Adaptive Threshold operation through two demand cycles:

    • We see that at 8:11 and 8:27 when pressure drops below threshold (flow begins) the threshold flips to above the psi to define when flow stops.

    • At around 8:14 and 8:33 the psi goes above the threshold, (flow stops), and the threshhold once again tracks below the newest max psi.

    

System Operation

• Based on appliance signatures, a 10 minute flow causes the valve to shut down unless the following conditions exist:
  • Motion is detected in the bathroom or kitchens, causing a 20 minute standby period.
  • The manual override switch has been actuated.
  • Detection of moisture by external sensors cause immediate valve closure.
  • Monitor daily leakage test and graphical representation to catch other issues.

Flow Duration Study

• Overnight activity followed by shower at 6 am.
  • Note visual sign of failing toilet seal, which was seen before heard:

• This is a great visual tool to monitor the water system. That seal is getting worse! Still can not hear it to identify it.

• Wash Machine flow and dishwasher signatures indicate max flow duration is only a few minutes.
  • Laundry:

- Dishwasher:

• Morning routine including shower:

Hardware

• PIR motion sensors with optional temperature/humidity report to Home Assistant, causing a 20 minute standby.
• Be sure to use a 100nf decoupling capacitor across temp sensor Vcc and Gnd to prevent spurious PIR hits.
• Use most any ESPxyz here. Standardizing with ESP32 keeps my life simple, if inelegant.
• Add a white Ailkin USB power adapter and some velcro tape to the assembly and plug it in.
  • The blue LED is easily visible when motion is detected.
• Software for the PIR sensor is at https://github.com/Bobbo117/Cellular-IoT-Monitor/blob/main/src/AmbientAP/AmbientAP.ino .
  • Enable HA so that it will communicate with home assistant or an alternative destnation.
  • Use CASA_1 ID 4 (kitchen), 5 (bathroom), and 6 (bathroom2) for up to three PIR sensors.
  • These IDs will send the topics kithcen/pir, bathroom/pir, and bathroom2/pir respectively.

Software

• Adjustments to the original Watermain software are minimal:
  • New variable definitions and mqtt topics are appended at the beginning.
  • New command topics are appended to the mqtt callback function.
  • New processing is appended at the end of the loop() function.
  • Two new threshold functions are appended at the end of the code after the loop function.

Tips, Tricks, and Traps

• If you take a long shower (> 10 minutes), verify that the bathroom motion sensor sees you! Look for the blue light.
• For showers longer than 20 minutes, don't forget to wave at the motion sensor once in a while.
• Activate the Manual Override switch in the HA screen for the powerwash vendor or other vendors using water.
• Keep an eye on the motion sensors. If one stops working, you could be in for a surprise in the shower at about 10 minutes.

Results

• This system has operated 6 months with no unanticipated shutoffs.
• Very slow leak rates may not close the valve, especially if the pressure happens to be on the up cycle.
  • In this case, the nightly Static Pressure Test gives an abnormally high reading that should be followed up.

Home Assistant Screens

• These screens along with Yang's will help you navigate your way through the software:

Conclusions

• While this adaptive threshold mechanism is not as sensitive as an impeller, it provides an added layer of protection without the expense.

• This is a great project for those who want to become as one with their plumbing system while simultaneously protecting against one of the more frequent and expensive insurance claims.