Simple Water Level Indicator Alarm with Buzzer


ByJayant 168

Simple Water Level Indicator Alarm Project

Water tank overflow is a common problem which leads to the wastage of water. Though there are many solutions to it like ball valves which automatically stop the water flow once the tank gets full. But being an electronics enthusiastic wouldn’t you like an electronic solution for it? So here is a simple and handy DIY water alarm project tutorial that will guide you to make a circuit which will detect the water level and will raise an alarm upon getting the water tank full or a preset level. 


This simple transistor based water level indicator circuit is very useful to indicate the water levels in a tank. Whenever tank gets filled, we get alerts on particular levels. Here we have created 4 levels (low, medium, high and full), we can create alarms for more levels. We have added 3 LEDs to indicate initial three levels (A, B, C), and one Buzzer to indicate FULL level (D). When tanks gets filled completely we get beep sound from Buzzer. If you want to improve the project by adding a display and automatic motor on-off control then you can simply add a microcontroller like Arduino to sense the water changes and control the display and motor accordingly, if you want more details about that project you can check out the Arduino based water level indicator and controller project.  


Components Required for Water Level Alarm Circuit 


Water Tank Overflow Alarm Circuit 

The complete circuit diagram for the water overflow alarm project can be found below. As you can see the circuit is simple and easy to build as it only has few basic components like transistors, resistors, LEDs and a buzzer 

Water Level Indicator Alarm Circuit

We can consider this whole circuit as 4 small circuits, each one for indicating/alarming, when a particular level (A,B,C,D) of water have been reached.

When water level reaches to point A, circuit with RED LED & transistor Q1 gets completed and RED LED glows. Similarly when water level reaches to point B, circuit with YELLOW LED and transistor Q2 gets completed and Yellow LED glows, same goes with point C. And finally when tank gets full (Point D), circuit with buzzer gets completed and buzzer starts beeping.


Low Water Level Alarm Circuit - Working

Here we are using transistor (of NPN type) as a Switch. Initially there is no voltage applied to the base of the Transistor Q1 and the transistor is in OFF state and no current is flowing through collector and emitter and LED is OFF (See below diagram to understand Transistor Pin structure).

Transistor Pin Structure

When the water level reaches to Point A in the tank, the positive side of the battery gets connected to the base of the Transistor Q1 through the water. So when a positive voltage has been applied to the base of the Transistor Q1, it gets into ON state and current starts flowing from collector to emitter. And RED LED glows.


You can see resistors (R1, R2, R3) at the base of each transistor, which is used to limit the maximum Base current. Generally a transistor gets its ON state fully when a voltage of 0.7 V is applied to the base. There are also resistors (R4, R5, R6) with each of the LEDs, to drop the voltage across LEDs, otherwise LED may blow up.


Same phenomenon happens when water level reaches to Point B. As soon as water level reaches to Point B, a positive voltage gets applied to the Transistor Q2, it gets ON and current started flowing through YELLOW LED, and LED glows. With same principle, GREEN LED glow when water level reaches to Point C.And finally Buzzer beeps when water level reaches to D.


Note that Left most wire in the tank must be lengthier than other four wires in the tanks, because this is the wire which is connected to positive voltage.


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  • Yashaswi's picture
    Nov 16, 2015

    Will this work in a large water tank?

  • mahantesh angadi's picture
    mahantesh angadi
    Oct 08, 2016

    yes it will works on large tank also

  • Joy Biswas's picture
    Joy Biswas
    Apr 21, 2017

    can i use this water lavel indecator for 500 liter tank ?

  • Ankit's picture
    Oct 18, 2016

    Yeahh it will definitely work for large tank yashh

  • Kalaimani's picture
    Feb 02, 2017

    Hi sir please send the Water level indicator using transistor

  • linkan's picture
    Oct 31, 2017

    its a demo project...if u will make a large base project then it will d concept z same...

  • Jayant's picture
    Nov 21, 2015

    Of course, it will work, but you need a proper installation.

  • kelly's picture
    Nov 26, 2015

    can a (BC547 or BC548) transistor be used instead of the BC507 transistor

  • Jayant's picture
    Nov 28, 2015

    We are already using BC547 transistor, any General Purpose small signal NPN transistor should work here.

  • Prakash Koppal's picture
    Prakash Koppal
    Nov 03, 2016

    ya you can use ....or any other general purpose transistors also

  • uk's picture
    Nov 29, 2015

    Sir may I use it in my 1500L tank .. Will it woperfectly ? And me fast sir.

  • Jayant's picture
    Dec 05, 2015

    As previously stated, it will definitively work in any tank but you need a proper installation, concept will remain the same.

  • pankaj's picture
    Dec 19, 2015

    Sir, why not you have used resistor with the transister connected with the buzzer?

  • Maddy's picture
    Jan 01, 2016

    Yes, you can also use current limiting Resistor for the forth Transistor, to prevent it from any kind of damage.

  • Priyanka's picture
    Dec 27, 2015

    Sir, will it work with long wires like from terrace to room

  • Raj's picture
    Sep 10, 2016

    yes priyanka its working
    before I complete the device and then I m using the device

  • sourav shome's picture
    sourav shome
    Mar 21, 2017

    What wil happen if i do not use 220 ohm resitor?

  • pragya's picture
    Jan 29, 2016

    Sir pls help ..
    I have arranged all rrquired components according to the given circuit bt the circuit gets completed at the transistor level nd the led strts glowing as i connect the battery to the circuit without placing those other ends in water .. Help me sir ..

  • mish's picture
    Oct 09, 2016

    hi same thing happening with me too. I made 2 circuits and 1 led glowed when i connected with the battery and with the 2nd circuit the buzzer is buzzing without pouring water. The circuit looks right but idk what the problem is? Can you help please. Thanks

  • hemantdhakad's picture
    Jan 29, 2016

    I am making your project but sir me use transistor bc548 so sir any problem
    Please rply

  • muzzammil's picture
    Feb 06, 2016

    i want to attach buzzer on each LED then what should i do, please guid...

  • Maddy's picture
    Feb 08, 2016

    you can directly connect Buzzers with LEDs.

  • Cesar's picture
    Feb 10, 2016


    How long is the maximum distance in meters form a 5 volts or 9 volts battery ? Like with an UTP network cable.

  • vineet's picture
    Feb 12, 2016

    Dear Sir,

    My query is that I want to install the system at ground floor and put the wires in the water tank located on second floor. For that I have to pull the wires for approximately 40 feet . So for such a long length wouldn't there be copper losses and would it function with 9V battery

  • Jayant's picture
    Mar 11, 2016

    The voltage drop is dependent upon the resistance of wire, load resistance and current through the wire. But roughly according to this circuit, we can use it upto 100-150 feets. You can check some online voltage drop calculators to find the accurate length according to your wire.

  • vikram shetty's picture
    vikram shetty
    Feb 27, 2016

    Sir as on 28 Feb we are celebrating science day I am going to exhibit this model but sir.... Asci have tested once I observed that the Buzzer will not scream loudly as it just sounds in small amount only like a whistle. so myvdoubt is ... Is this buzzer will be able to warn the person.... Plz reply

  • Jayant's picture
    Mar 11, 2016

    You can either use some Alarm with external power supply and transistor as a trigger or You can use AC alarm with a Relay in place of Buzzer. Check How to use Relay here.

  • Siyam's picture
    Mar 22, 2016

    Hi, I have made this water level indicator but it is not working properly because the water is not connecting the wires inside it. However when I put salt in the water it works. If possible help me in this issue.

  • Jayant's picture
    Mar 29, 2016

    Probably you are using Purified Water or Distilled Water, which does not conduct electricity. And after adding salt (ionized substances), it becomes conductor.

  • Naseer Hakeem's picture
    Naseer Hakeem
    Mar 26, 2016

    what is the limitation of this project?

  • ankit tomer's picture
    ankit tomer
    Mar 29, 2016

    sir, i have completed this project on pcb board with proper designing of pcb.but the problem is that not even a single LED is glowing.can you please suggest where may be the fault??
    and sir i have connected the base of the transistor to the sensor,emitter to -ve termonal of battery and collector to LED.Is it right,sir??

  • Jayant's picture
    Mar 29, 2016

    This is a very simple circuit and should work without any issue, have you connected LED terminals properly according to polarity.

  • Sunny Yadav's picture
    Sunny Yadav
    Mar 29, 2016

    Can I connect a motor instead of led or buzzer??
    Once water reaches certain level , motor should start??

  • Hasan's picture
    Apr 01, 2016

    Can I use motor by replacing the buzzer ??
    Is any possibilities here when the water will have reached the top of the tank then the motor will off??
    I mean the pump motor which is using to enlarge the water level of the tank!!
    Can I use motor by replacing the buzzer ??

  • Abhishek's picture
    Apr 02, 2016

    @Hasan and @Sunny Yes you can use Pump motor. A Relay will be used for this. To switch Off the motor, use Relay with PNP transistor and to switch On the motor use Relay with NPN transistor. Check this for Relay connections

  • amit's picture
    Apr 02, 2016

    Shall I use 12 v battery instead of 9 v

  • Vikas's picture
    Apr 02, 2016

    Why do we need the transistor, i know that it works as a switch here, but what happens if i directly connect the led cathode to the wire and drop it into the water instead of connecting the transistor? Theoretically it will work, but what happens if I implement it practically?

  • Abhishek's picture
    Apr 17, 2016

    Water is not a perfect conductor, but it can conduct enough to trigger Transistors to Glow LEDs. Hence Transistor is also used here as Amplifiers.

  • Shubham Sawant's picture
    Shubham Sawant
    May 27, 2017

    You can do this by increasing current of supply by using mobile charger or else and check with multimeter to find excess voltage to use appropriate resistor.
    I have made such a working circuit and using it in perfect working condition.

  • Sunaabh Sarkar's picture
    Sunaabh Sarkar
    Oct 30, 2017

    Most mobile chargers are small SMPS devices that reduce the mains voltage to 5.1v etc etc, and usually there is no isolation of the mains from the output, so one runs the risk of electrocution if a mobile charger is used to run the device so a mobile charger would not be a good idea to power the device. Use a 9v battery or a power supply using s step down transformer... the battery eliminator kind of thing.

  • venkatesh's picture
    Jun 29, 2018

    conductivity of water is less compared to conductor.power loss is acquired in water so it not enough for gloving led.we are using trasister required 0.7v input for switching transister.

  • anusha's picture
    Apr 03, 2016

    Sir ,What happens if we change the resistor values?? And can i replace the buzzer with an 8 ohm speaker.if yes shall i need to connect resistor at fouth trasistor also??

  • Joe Jose's picture
    Joe Jose
    Apr 07, 2016

    Hi, I have made this water level indicator but it is not working properly because the water is not conducting elecyricity. If possible help me in this issue.

  • neel gohel's picture
    neel gohel
    Apr 08, 2016

    Can i used bc-548 transistor?
    Nd can i used 470 ohm registor insteand of 230ohm registor?

  • Abhishek's picture
    Apr 17, 2016

    @Joe: Check above comments for Water conductivity problem.
    @neel: Yes you can use BC548 and 470 Ohm resistor

  • mahi's picture
    Apr 11, 2016

    may i use transformer instead of 9v battery?

  • Gopi's picture
    Apr 13, 2016

    Instead of long wire, I want the circuit for wire less.please

  • Shanmuk 's picture
    Apr 15, 2016

    May I get single led glow at particular level.if possible can you suggest me I am facing difficulty with that.

  • som's picture
    Apr 15, 2016


    The buzzer will produce a steady sound. Instead of that, if I need to sound like a siren, then how I can achieve this. I assume some capacitor/resistor may solve the problem. But I don't know how to connect those components to the base of the transistor.

  • som's picture
    Apr 15, 2016

    Dear - How to make the buzzer sound like a siren instead of just producing a steady sound?

  • falesh's picture
    Apr 16, 2016

    Can I increase the no of LED indicators to 7 by repeating the Transistor circuit 4 more times?

  • Yogendra Singh's picture
    Yogendra Singh
    Apr 19, 2016


    i made the circuit according to above shown figure but i connect mobile charger as a source in place of 9v battery all LEDs works fine but there is problem with buzzer there is no sound from it when i complete circuit by dropping wires in water tank but it works fine if i connect wire directly..

  • Gayan's picture
    Apr 21, 2016

    How can use this circuit reverse type. Because i wan't measure water level in my water well. Actually I want low level indicator. Water level is gone down i want indicate the led. How can use this. Pls help me.

  • Abhishek's picture
    May 06, 2016

    Use PNP transistor BC557 in place of BC547 and reverse the order of LED/buzzer.

  • Lokesh's picture
    Apr 26, 2016

    What is the least Price for this indicator??

  • Aju mallik's picture
    Aju mallik
    Apr 29, 2016

    Thanks sir.

  • Tahir Aleem's picture
    Tahir Aleem
    May 04, 2016

    sir which type of transistor we are using in this project i mean pnp or npn???

  • adithya's picture
    May 12, 2016

    sir can we make this circuitju without transustor and resistor...

  • mehedi hasan pavel's picture
    mehedi hasan pavel
    May 15, 2016

    sir,how much money to be used for this project?

  • Maddy's picture
    May 17, 2016

    This demo project can be made in less than 100 Rupees.

  • Junaid's picture
    May 17, 2016

    The circuit is complete when voltage flows through the water.. But if the voltage flows, then the current may also flow. So, if I use it for my houses tank, would current flowing in the water be a problem, or the water does not get electrocuted, please do give me a quick and sufficient answer.

  • Maddy's picture
    Jul 12, 2016

    Yes current will flow through the water, but current from 9v battery is not harmful.

  • ajithkumar g's picture
    ajithkumar g
    May 24, 2016

    Hear after I try this

  • Dureste's picture
    Jun 10, 2016

    Thank you for the briefing man! but is it necessary to use a battery? is there any change that would happen if i apply a bridge rectifier circuit instead of battery? if yes, do i have to change the resistor value if the output of rectifier is 12v?? thanks man.

  • dharmendra's picture
    Jun 13, 2016

    Sir.. I complete the ckt. Of water level indicator bt one doubt is that if my tank is full then buzzer will start bt till the level of water is full the buzer will operate on for long time so how i can stop to this

  • kaushik's picture
    Jun 14, 2016

    Dear sir,
    How we convert 5-9 V into 220/230V ??
    Please tell me...

  • Bobby 's picture
    Jul 02, 2016

    respected sir
    can i use transformer in place of 9 V battery and motor as buzzer
    if yes
    what will be connection

  • Waqas's picture
    Jul 10, 2016

    For how long will the buzzer sound? I mean, once you are alerted, how can you stop the sound of buzzer? turning the circuit off wouldn't be a good idea as it would be in efficient to turn the circuit on and off again.

  • vipool's picture
    Jul 11, 2016

    the buzzer used in this ckt is having very low sound . i want to increase the strength of the buzzer or use some other device for that purpose. what is the solution for dat?

  • Maddy's picture
    Jul 12, 2016

    Trigger some 220/110V AC alarm with the help of Relay and be careful while working with 220v, it can be lethal.

  • Muhammed Husseini Danjuma's picture
    Muhammed Hussei...
    Jul 15, 2016

    i need help on this very topic of the project.

  • sandeep's picture
    Jul 21, 2016

    will i give home voltage to it

  • waleed's picture
    Jul 26, 2016

    why not we use PNP instead of NPN. let suppose we use PNP what will be the impact on the circuit.

  • Arun 's picture
    Jul 29, 2016

    Super idea sir...But I have to implement using wireless technique sir..I have an Arduino board..Give me an idea sir

  • Abhijeet Gawande 's picture
    Abhijeet Gawande
    Aug 01, 2016

    Sir, the circuit is working properly on 9v battery.but I have used a 9v transformer here and seven colors led .the problem is that,I am getting the output but the led's a are not blinking and the buzzer is not making proper sound.
    Please help.

  • John's picture
    Aug 04, 2016

    If we add a diode in the forward biased direction anywhere in the circuit, will it change the outcome?

  • shiv singh's picture
    shiv singh
    Aug 24, 2016

    Transistor burn when prob short please give the solution of prob short transistor not burn.
    shiv singh

  • waleed sajjad's picture
    waleed sajjad
    Aug 24, 2016

    Can anyone tell me how to use buzzer at low level to indicate empty tank?


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