Measure pH in Remote Tanks Without Degrading the Electrode?

Projects General Guidance
1

I'm working on a system to measure the pH of water tanks located in remote areas. I only need to take measurements 3–4 times per day, but I'm concerned about the longevity of the pH electrode.

Here are the constraints and current ideas:

  1. Continuous immersion

If the pH electrode is left immersed in the tank water (which is not clean but not highly contaminated—think of rainwater runoff), it may degrade faster due to fouling or long-term exposure.

  1. Sampling Pot approach

One idea is to use a small sampling chamber that fills with water from the main tank every 6 hours. The measurement would be taken from this small pot, which is then flushed and emptied. However, I'm unsure whether this setup would help.

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I came across a helpful video from Hanna Instruments about common mistakes when using pH probes: https://www.youtube.com/watch?v=OXPAXNILHu8

What would be the best practice to implement reliable and long-term pH monitoring in this scenario? I'm looking for suggestions that balance electrode lifespan, accuracy, and maintenance effort.

2

Maybe with pH Measurement with Contactless Radiofrequency Sensing!?

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3

have a look at Atlas Scientific EZO™ pH sensors

have used them with ESP32 microcontrollers connected via I2C interface

how remote are the locations? how will you monitor the sensors?

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4

I would be too, and I don't think it is an easy problem to solve. I've seen adverts for "new" types of electrodes that are claimed to be function after being immersed for months or years in water such as you describe.

I'm skeptical, and only long term experimentation would reveal the truth. Laboratory grade pH electrodes would not be accurate after many days of such exposure. Here is a fairly recent study of the lifetime of glass electrodes: Over One-Year Long-Term Laboratory Tests of pH Electrodes in Terms of Industrial Applications Checking Stabilities of Their Parameters and Their Influence on Uncertainties of Measurements - PMC

On the other hand, why would you expect the pH of water in a tank to change in a fraction of a day, and why is it important to know the pH?

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6

The locations are situated in hilly areas, and I'm using LoRa gateways to collect the data, which is then sent to a central server.

7

I'm developing monitoring devices for a client who stores rainwater in tanks across hilly areas for household distribution. The goal is to measure pH, TDS, and other water quality parameters at specific intervals based on their requirements.

8

That will be acidic by default! Is the water in the tank continuously circulated? If not the any solids will settle to the bottom.

9

It's a sampling pot where water is added only when needed for sampling. After taking the sample, the pot is emptied.

10

The pH of rainwater will typically be around 5.5 to 5.6 because of dissolved CO2, which reacts with water to form carbonic acid, a weak pH buffer. In cities and other areas of very high air pollution, it will drop to lower pH.

As stated above the water will always be clear, because solids will settle to the tank bottom, and the TDS will be around 4 uS/cm unless the environment is very dusty.

The real concerns are cancer-causing dissolved PFAS and related compounds, which are ubiquitous world wide. I have the water tested commercially and since the PFAS levels are significantly higher than safe levels, remove them to below detection levels using an activated carbon filter.

I have been enjoying and maintaining a household rainwater system for over a decade and highly recommend it!

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