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.


Have any question realated to this Article?

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This question is already answered in above comments, please check. Further use PNP transistor BC557 in place of BC547 and reverse the order of LED/buzzer.

Submitted by Fahad on Wed, 09/07/2016 - 16:34


Can I use a 9V/2A output from a (AC to DC) transformer instead of the battery ?

Submitted by logapriya on Thu, 09/08/2016 - 19:22


Can u pls suggest me a simple project based on resistors, capacitors and inductors..

Submitted by samuel on Fri, 09/23/2016 - 17:03


can this be used with Ac supply directly from mains and we use a power diagram which comprises of a rectifier, a transformer, a voltage regulator and a capacitor

Submitted by Ceejay on Mon, 10/03/2016 - 18:31


Good project thanks for sharing. I have a question....I am doing a similar project but with capacitive oil level Sensor which measures the quantity of oil in a Tank. I also have to measure low (1/4), medium (1/2), high (3/4) and full (1) using two capacitive parallel plates. Can I use almost the same circuit diagram?? Or how would it be like??

Submitted by shahin on Sun, 10/09/2016 - 12:20


Can you please tell me the role of the transistors. The transistor configuration is for a switch then how can it act as a amplifier?

Submitted by Madani on Sat, 10/29/2016 - 11:45


Can I use 5 V DC power supply from solar system, instead of 9 V to supply two circuits indicators.
Is the circuit should be modified for 5 v DC or not.

Submitted by nikhil on Tue, 11/01/2016 - 19:12


good use for exhibitions and competition nicely done good job

Submitted by Matt on Thu, 11/24/2016 - 21:30


Hi, I just want to ask how long can be cables A,B,C,D which leads to water tank. Because I want try this 9V solution but I need at least 10 meters long cables because of distance to water tank.
Thanks in advance.

Submitted by sreenivas on Sat, 11/26/2016 - 07:43



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 ??

If yes, how can i made necessary changes in circuit..?

And due to long distance; may i use wireless...?

Please revert me with necessary suggestions.


Submitted by Ammad on Sat, 11/26/2016 - 22:23


sir ,
I use 12 volt transformer and bridge rectifier instead of 9V battery but i'm facing problem with my buzzer its not work properly ,its giving wheezing sound I'd checked my circuit several time its wiring is okay and My led's also work well , And One more problem when i take 20 feet 5 core thin telephone wire i'm facing current leakage problem between wires, LED's glow dim even without touching any Ground and positive. Please any suggestion

Submitted by vinod on Sun, 12/25/2016 - 14:07


yes i am also make this project and i have copleted with good working
i think u may miss 1 thing negative suply is conect to other ends of all leds and buzer and also positive is goes into the ground of water which provide continue suply for each leds
so check ur circuits
thank u

Submitted by nitin on Sat, 01/28/2017 - 18:04


I made this with smps and an a88 chip.but how it worked can explain its working with smps and a88 chip
Sir reply me fast on the above email

Submitted by srivatsav on Thu, 02/09/2017 - 03:03


Wonderful it has worked, awesome. I extended it with 7 level indicator using cat 6 ethernet cable for the connectivity from tank to ground floor, used 9V power adaptor for continue monitoring. working superb.

Submitted by Walid Nasr on Wed, 03/15/2017 - 14:49


what size wire needed if LED diodes and battery(ies) are mounted 20 meters from water reservoir, with additional 4 meters depth of reservoir

Submitted by flash on Sat, 04/08/2017 - 20:23


Everything works fine but when the water level reaches the last sensor, the other two leds dim. Also the buzzer produces an extremely faint sound. The wire is approximately 15 meters. All the other components are as prescribed. PLEASE HELP!!!!

Submitted by Ehsan on Wed, 05/03/2017 - 02:06


Hi. When u put copper wire in the water, after a while , it will be lost , it will be anodized . What material should be replace to solve this problem ??

Submitted by junaid on Sun, 06/25/2017 - 09:38


sir I want a reverse process like if probes is in water my buzzer of otherwise it will on so what can I do. I tried many times with different circuits using the not gate and by using PNP transistor the problem is when i touch the probes it will work and when i put them in water it wouldn't what can i do please help??

Submitted by kheder on Fri, 07/28/2017 - 23:17


Sir, i want use this water level indicator for a long meter over 100 m for water wells in the ground. Are this circuit will be work well

Submitted by Dilan Vidurinda on Wed, 08/02/2017 - 18:58


HI i tried with this circuit diagram and it worked but only the LED s it didnt make any responce by the buzzer .my buzzer ia working but whem i connect it to this circuit it doesnt make beep.

Submitted by deva on Fri, 08/25/2017 - 15:38


hai sir,
if i goes to install a speaker like alarm speaker what will happen or what are the modulation are need in this same ckt

Submitted by Umar Ismail salifu on Thu, 10/12/2017 - 06:08


Please sir am a mechanical student and I have seen this project as a good project and I wish to use it as my project work, please sir can I use it.

Submitted by Arijit on Fri, 10/27/2017 - 18:41


When transistor is on then emitter and collector is connected.I think there has no connection between base and led. So tell me uses and how r4,r5 and r3 registers are working?

Submitted by Harry on Thu, 01/25/2018 - 03:51


Sir in our project, we are planning to attach a 12Volts wireless alarm system. in what part of the diagram can we insert the transmitter of the RC?

Submitted by gotti venky on Tue, 01/30/2018 - 10:24


sir how use this at our home i want to need some help

Submitted by Ashish Kushwaha on Mon, 02/05/2018 - 23:27


such a GREAT article to work on. Thankyou for sharing this information. I hope this will help many people. you can also check out my article

Submitted by John McLaren on Thu, 03/01/2018 - 18:01


Hi sir
I want to use this in a stainless steel tank that is in a motor home. The tank is earth back to the chassis as NEG earth. Can I use this as it is pos as the live in tank. Is this a problem??

Submitted by Raghu Nath Mathur on Mon, 03/05/2018 - 19:30


I have made the water level indicator which worked fine for a few days . But now the LEDs keep glowing even when the water level goes below the set level . Earlier the LEDs kept glowing only for 20-30 seconds after the level went down the set level

Submitted by Faisal on Sun, 06/17/2018 - 19:59


I saw some circuits without transistors, resistors directly connected to water. What is the differences.

Submitted by karl on Sat, 07/14/2018 - 23:18


thank you so much for your post about this project it's a good idea.
but please may you give us the block diagram of that circuit water level indicator alarm

Submitted by Sagvan on Fri, 08/03/2018 - 21:29


Dear Sir,
I have tried this method but the wires in the water produce bubbles and the positive wire produces something like smoke. I need some help, please!

Submitted by karl on Thu, 08/23/2018 - 01:04


i need your help plzzzz
when i will runn this project may i use motor pump? i want to do this project as s6 final project at school

Submitted by Wan on Tue, 09/04/2018 - 14:06


Since water will be used as conductor in the circuit, can we use the water from the tank or is there possibility to get electrocuted?

Good project.congrats. sir I have a doubt,
1. why using transistor. can i do this project only using battery, resistor,and L E D(that is, without use transistor)? What is the use of transistor?

2. What is the its principle of this project?

What will happen if power suplly increased to 12 volt DC. What are the parts required to be changed keeping intact other components except the  resistors. Please advice.