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Anyone using the Arduino as a water meter?

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    Anyone using the Arduino as a water meter?

    Use case is this.... I have a saltwater aquarium and have to create saltwater for water changes. I need the ability to measure the water being created by my RO system in exact increments. The input is 1/4" tubing (like to an ice maker). It is low pressure and would take half a day to create 50 gallons.All sorts of automation I can add to that if I can solve the measurement piece....

    Anyone have a thought on how to slay that dragon?

    Thank you,


    Plenty of examples online:


      This is not so much an Arduino problem as it is a sensor problem.

      How accurate does your flow metering need to be? Being that this is a salt water tank I am guessing fairly accurate. Additionally, the sensor needs to be tolerant of salt water and not be constructed of materials that would drastically alter the chemistry of the water you are trying to measure.


        Yes, exactly on the sensor issue.... I like to mix 50 gallons at a time. If it was between 49 and 51 the chemistry would be fine. The good news is that I am measuring pure H2O into a holding tank.

        Steps :

        1. Add 50 gallons of reverse osmosis (pure H2O) into holding tank (this is what need measured) instead of me watching and hoping I am in the room when 50 gallons is added to the holding tank....
        2. Add chemicals by weight to create "sea water"
        3. Using an Apex Neptune DOS unit do a continuous water change (This is salt water tolerant)

        Repeat every week-end

        If I can accurately measure the feed I would be able to add sensors to tell me when the holding tank drops below a given level as well.

        Thanks for the thoughts



          How about using float sensors typical for wet situations? Such as

          This could get you the low and full water levels.

          ​​​​​​​While it won't get you an exact measurement, it would be close allowing you to do step 1, then finish the fill manually and add chemicals in step 2.


            It appears you just need one measurement of 50 gallons. I use flow sensor/Hall effect for my RO to know when to change filters. This is not sufficiently accurate using common flow sensors.

            I have also used, but again without the necessary accuracy.

            What I would do for sensing is something like water leak sensor where probes are precisely placed so 50 gallons will trigger the leak. If your container is tapered at top the accuracy will be improved.

            I use the Aqara Zigbee devices. I have also deployed Dlink WiFi devices to sense water leaks. There are also very cheap leak detectors that could be interfaced to Arduino.

            To assure conductivity I would first put the chemicals in the container.

            The second part is some form of valve to stop the water. I have used WiFi for 3/4” servo valve, but this is overkill for what you need. Some solenoid valve like the little brother of what is used in washing machine or dishwasher should work. I have no specific product in mind.


              Have you considered a float that measures height in the container. Similar to a toilet tank valve. You could also time the fill and then open a control valve for a specific period of time for a less complicated fill.


                Here is a sensor that might work. Mount it pointing down into the container so it is at the spot where the container is filled with 50 gallons.


                Or this one which can be attached to the side of the container. You could place it so that the sensor could register a


                Both sensors have example code you can use when programming your Arduino or what ever processing board you plan on using.


                  For something like this a float switch should be simple, easy, accurate and effective. for a more Rube-Goldberg solution, you could go with weight by putting the water tank on a counter balanced teter board with a microswitch. Should be extremely accurate and repeatable. I use Ultrasonic sensors for my 3000 Gallon and 5000 Gallon water storage tanks and they work OK for that application but I think they would be too expensive and there is a Signal to noise issue that might make for false readings occasionally. Not sure if the pure water will trigger a moisture sensor but if so, then that is another simple sensor when you just want to know when a specific level is reached. .