Simple Water Level Indicator Alarm with Buzzer

Published  May 15, 2015   168
J Jayant
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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Submitted by Priyanka on Sun, 12/27/2015 - 19:30


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

Submitted by Raj on Sat, 09/10/2016 - 05:42

In reply to by Priyanka


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

Submitted by pragya on Fri, 01/29/2016 - 20:13


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 ..

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

Submitted by hemantdhakad on Fri, 01/29/2016 - 20:13


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

Submitted by muzzammil on Sat, 02/06/2016 - 01:07


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

Submitted by Cesar on Wed, 02/10/2016 - 22:23



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

Submitted by vineet on Fri, 02/12/2016 - 15:27


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

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.

Submitted by vikram shetty on Sat, 02/27/2016 - 19:47


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

Submitted by Siyam on Tue, 03/22/2016 - 18:11


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.

Submitted by ankit tomer on Tue, 03/29/2016 - 11:33


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??

Submitted by Hasan on Fri, 04/01/2016 - 15:57


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 ??

Submitted by Vikas on Sat, 04/02/2016 - 17:53


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?

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.

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.

Submitted by anusha on Sun, 04/03/2016 - 23:09


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??

Submitted by Joe Jose on Thu, 04/07/2016 - 11:58


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.

Submitted by som on Fri, 04/15/2016 - 10:52



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.

Submitted by Yogendra Singh on Tue, 04/19/2016 - 23:55



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..

Submitted by Gayan on Thu, 04/21/2016 - 20:34


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.

Submitted by Junaid on Tue, 05/17/2016 - 02:11


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.

Submitted by Dureste on Fri, 06/10/2016 - 13:48


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.

Submitted by dharmendra on Mon, 06/13/2016 - 23:34


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

Submitted by Bobby on Sat, 07/02/2016 - 21:48


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

Submitted by Waqas on Sun, 07/10/2016 - 12:30


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.

Submitted by vipool on Mon, 07/11/2016 - 07:56


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?

Submitted by waleed on Tue, 07/26/2016 - 10:57


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

Submitted by Abhijeet Gawande on Mon, 08/01/2016 - 14:09


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.

Submitted by waleed sajjad on Wed, 08/24/2016 - 20:59


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