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    This is one of the simplest water level indicator that can give up to 7 indications – Full, Half and Low water levels in the overhead tank through LED indications. The circuit is simple and uses a single IC and a few components.

    The main part of the water level circuit is the 7 channel Darlington array IC ULN2004. Its seven inputs are connected to seven probes to sense the water level and the corresponding outputs are connected to three LEDs through current limiting resistors. A common probe (common) is connected to the positive rail. When this probe gets electrical continuity through water with the other probes the corresponding LEDs light.

    Schematic of the Water level Indicator Circuit

    led water level indicator

    Here is an idea how to connect the 7 segment display.


    Assemble the circuit on a common PCB and enclose in a small box. This unit can be kept in a place for easy monitoring. Use brass or chromium plated pins as probes. Connect the probes with the unit using three core shield wire. Probes should be plugged into the tank through the side. The low probes in the lower position, half probes in the middle positions and high ones in two upper position. If the tank is empty, no LEDs will be on. When the water level increases the green LEDs (marked with G) will start to light up according to the H2O level. When the tank becomes full the red LEDs (marked R) will be on. In short, if Green, Yellow and Red LEDs light, tank is full.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    36 Responses to "Simple Water Level Indicator"

    1. Sir,
      i appriciate your work. but i want a physical modal of the same for the boiler drum is it possible with the halp of the same.
      give me reply.

    2. Sir , nice circuit & usefull

    3. a very worthful circuit. sir could you please tell me how to interface this circuit with microcontroller 8051. as we are making a dam water level warning system and controlling using gsm.

    4. Dear sir,
      can i use a alarm in this circuit???
      >When tank full, alarm active and make some noise.
      Please tell me where i connect the Alarm.
      also provide the alarm circuit.

      Your student,

      • Chandra prakash says: on September 28, 2013 at 7:37 pm

        Just connect a pezo buzzer between full level(Pin10) to positive of battery. I did it for my 2 homes and third one in in progress.I am using 12v 1amp dc adaptor in replacement of 9-12 v battery.

      • Yes u can by replacing the led with alarm or connect in a series with alarm

    5. mmmm ALARM ???

      ok…let me anserwed and help to a P.Marian…
      choice an output ( depend how you accomodate your exits …and apply a buzzer
      or insert a sound alarm noise

      some one visit this web

    6. zishan haider says: on May 11, 2012 at 8:32 pm

      can i use a alarm in this circuit???
      When tank full, alarm active and make some noise.
      Please tell me where i connect the Alarm.
      also provide the alarm circuit.i need it sir reply me its toooo urgent….

    7. sir,
      I have required the IC ULN 2004 for water level control device.Can u provide

      Thanking Avinash

    8. Can we use AC current to make it work?

      If yes, How much volt can we need to use for this circuit.

      Do we have to make any changes to resistor?

    9. No, it will not work on AC. To power via AC, get a wall wart power adapter –check recent article on wall warts.

    10. Can i use a component that convert AC and give me an output of 9V DC for this circuit. Or it has to be 9V Battery.

    11. Hi,

      Circuit works fine and i have connected Buzzer too. However, when i immerse the probe in the water the LED glow is dimmed and Buzzer is sounding very low. Can you tell me what needs to be done to avoid this since i am planning to implement this for my overhead tank.

      • k.bhojane says: on February 1, 2015 at 11:52 am

        Ed on November 19, 2012 at 8:06 pm
        Hi, Circuit works fine and i have connected Buzzer too. However, when i immerse the probe in the water the LED glow is dimmed and Buzzer is sounding very low. Can you tell me what needs to be done to avoid this since i am planning to implement this for my overhead tank.

    12. Sir,
      I want to use this circuit for a well to know the water level. What will be the life of battery. Can i switch ON only when i want to know the water level.

      • Yes, of course. You can switch it on only when you need it and then turn it off, and that will save your battery.

        In that case, you can also use a push button in parallel with your power switch, so that instead of turning the switch on-off, click-click, you can simply press the push button to get the level indication.

    13. Hi,
      First of all I must thank to the publisher for this valuable circuit. I kindly like to add something. First look at the structure of the ULN2004 (http://avrlab.com/upload_files/ULN2004_structure.JPG)

      The circuit has used only 3 pins but can use 7 pins which simply we can have 7 sensors with 7 LED bulbs. So I think it will be working fine. I want your advises and thanks so much in advance.

    14. sir.., good evening.. may I know that to which I can interface to switch off the motor, when the tank is full?

    15. simple and very useful project. Thanks for sharing. There is another circuit on water level indicator which I have seen few days back. If anybody interested, visit http://www.electronicshub.org/water-level-indicator/

    16. any software for water level indicator.

    17. stimate domn:am si eu o intrebare;acest montaj poate fi folosit ca si indicator pentru nivelul de benzinna?sunt un ampatimit al masinilor vechi si sonda din rezervorul cu pricina nu mai functioneaza.daca da ce modificari trebuie aduse montajului?cu stima

    18. Sir i have made this project but problem is that when the any senses comes to water contact then corresponding led and some other led also glow with this sensors so sir pl. guide me what is the problem behind this pl. give solution for complete the project. thanks

    19. sorry to respond late, I want to do this project to measure levels of benzina.its possible?

    20. Thanks to you…
      Super circuit…
      I need a small help,i need to add a buzzer..
      Please give the detailed circuit..
      I have tried a lot with pin 10 and others but it leads to failure..
      Please help me to connect the buzzer..
      Give the details about,where to connect the positive and negative terminals of a buzzer..

      • Use a transistor to amplify, say BC548 will be fine.
        Or alternatively connect the buzzer (+) to Vcc and (-) to ULN 2004 pin 10 or 16 (depends on your high-low sensor arrangement).

    21. I am looking for two different items.
      1. Round PCB having inside diameter of 47 mm and outside diameter of 55 mm with 4 LED installed on it as indicators (all one colour) to work on 230 V. Can I get a supplier for it for bulk purchase in Mumbai, India.

      2. I need a circuit to be installed in a blender for
      Controlling speed, Timer 30 seconds interval up to 300 seconds (10 steps), overload protector with warning Buzzer. To work on 230v AC. The buzzer will operate if the load current crosses 2.2 amps, the buzzer will warn the user for 20 seconds, if the user doesn’t stop the blender, the blender motor will stop automatically after 20 seconds. Motor will have 20000 rpm, it’s universal motor, drawing 1.4 amps current on no load and upto 2.2 amps on load. The minimum step less switch speed for motor will be 13000 rpm and maximum will be 20000 rpm.

    22. Well I’ve made this sensor using ULN2004 year ago, everything just working fine and perfect!
      The only issue that wasn’t resolved is the electrolysis on the water involving the metal probes with its 12VDC current. I was ended up with the water inside the tank turns a bit brownish, of which I would believe the water was just becoming not hygiene and getting polluted somehow.
      It was copper probes used in my 1st trial, then I tried alum probes but still not that convincing.

      With the copper probes possessing DC current, I suspect the reduction and oxidation reaction was occurred separating the ionic fraction of water and end up with the forming of Cu(OH)2 + H2, and of course the water turbidity.

      I would be happy to hear any solution or experience from all of u.

      • Hi, I have the same problem. I did this in a big rain water tank (3500l). I used ULN2803 which should be even more sensitive. It all worked fine for a month, but now only two lights out of 10 work. I tested the board and lights and they are working. So the problem must be in the contacts in water. Is it possible that copper oxidated or something like that which increased resistance too much?

    23. In water level indicator..
      buzzer make a sound to much law
      its due to because of battery ????

    24. Sir. Could u tell me 7 simple leveling devices, stating how each one is used

    25. Sir I liked this and wanted to know how it works

    26. I need bath pull indcator project report of it

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