Step-by-Step Guide
Understanding Pressure-Based Water Level Monitoring
Pressure sensors provide a reliable way to monitor water levels in tanks, canals, lakes, or any other water storage system without requiring visual inspection or sight glasses. This approach is particularly useful when you need remote monitoring capabilities and want to avoid manual checks.
The fundamental principle behind pressure-based level monitoring is straightforward: water pressure increases with depth at a consistent rate of 0.433 PSI per foot of elevation. This means a 20-foot tall tank will read approximately 8.66 PSI when completely full (20 feet × 0.433 PSI). When the tank is half full at 10 feet, the pressure reading will be approximately 4.3 PSI. When nearly empty with just one foot of water remaining, the sensor will read 0.433 PSI.
The exact pressure reading when full doesn't need to be precise—whether it reads 8.67 or 8.23 PSI doesn't matter. What matters is that you'll get the same consistent reading every time the tank reaches that full level, allowing you to establish reliable reference points for monitoring.
Common Use Cases and Goals
A typical application involves monitoring a rainwater collection tank that also captures air conditioning condensation for irrigation use. In such scenarios, you may want to achieve several goals:
- Monitor water levels remotely without walking to the tank location
- Know when the tank is at 25%, 50%, 75%, and 100% capacity by checking a phone or computer
- Automatically stop using the tank water source when it reaches 25% full to prevent pump damage
- Avoid drawing sludge from the bottom of the tank
Required Equipment
To implement pressure-based water level monitoring, you need only two components:
- A pressure transducer with a quarter-inch connection
- A pressure biCoder (which converts the 4-20 milliamp analog signal from the pressure transducer into a digital signal readable by the two-wire system)
The biCoder is essential because pressure transducers output analog 4-20 milliamp signals, which must be converted to digital signals for integration with the controller system. The 4-20 milliamp standard is common across many industrial devices, and the biCoder opens possibilities for connecting other compatible sensors.
Installing the Pressure Sensor
1. Thread the pressure transducer into a tee fitting at the bottom of the tank. The recommended installation method is to mount it sideways rather than facing upward, as an upward-facing orientation could collect debris inside the sensor.
2. If using an outlet fitting at the tank bottom, thread the sensor into that accessible location.
3. For lake or pond applications, you can use a zero to five PSI lake transducer designed to be suspended. These models come with a vent tube and protective plastic cap to prevent debris entry, but are otherwise identical to standard pressure transducers with the same threading.
4. If you cannot thread the sensor into a fitting, suspend it and drop it into the water body. This hanging installation method works well when bottom-mounted fittings aren't available.
Assigning the Pressure biCoder in the System
1. Navigate to the Devices section in your controller interface.
2. Assign the pressure biCoder to ensure the system recognizes the sensor input.
3. Verify that the pressure sensor appears in your device list and is properly connected.
Monitoring Pressure Readings in Quick View
1. Access Quick View to create a dashboard for at-a-glance monitoring of your pressure sensors.
2. Locate your pressure transducer in the Quick View display to see the current pressure reading.
3. Interpret the readings based on your tank's full capacity.
For example, if your full tank reads 8.66 PSI, you can determine fill levels as follows:
- 8.66 PSI = 100% full
- Approximately 6.5 PSI = 75% full
- Approximately 4.3 PSI = 50% full
- Approximately 2.2 PSI = 25% full
- 0.433 PSI = Nearly empty (one foot of water remaining)
- 0 PSI = Completely empty
4. Note the pressure reading when your tank is completely full—this establishes your 100% reference point for all future monitoring.
Setting Up an Empty Condition Based on Pressure
1. Navigate to Flow Setup in your controller interface.
2. Select Water Sources from the available options.
3. Choose Edit to modify the water source settings.
4. Add an empty condition, but instead of basing it on a soil moisture sensor (as you might in other applications), select the option to base it on pressure input.
5. Select the correct pressure transducer from the list of available sensors.
6. Configure the threshold by setting the condition to trigger when pressure falls below 0.433 PSI (representing approximately one foot of water remaining).
7. Set a wait time of 60 minutes before the condition activates. This delay prevents false triggers from temporary pressure fluctuations.
8. Enable the empty condition to activate the protection.
Once configured, when the tank drops to one foot of water remaining, the system will take the water source offline after the 60-minute wait period. This prevents the irrigation pump from running dry and burning out, and also prevents drawing sludge from the very bottom of the tank.
Video Walkthrough
Video originally published December 2022.
If you have questions, here are 3 ways to get answers:
1. Search within this HydroPoint knowledgebase
2. Visit the HydroPoint support page
3. Call 800-362-8774 or email support@hydropoint.com, hours are Mon-Fri 3:00 AM – 6:00 PM PT and Sat 9:00 AM – 2:00 PM PT.