Water level Controller

Water level controller circuit

Note:- We have developed another water level controller circuit using micro controller AT89S51 from Atmel. If you are interested, read that too :- Water level controller using micro controller

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A simple but very reliable and effective water level controller circuit diagram is shown here. The circuit uses 6 transistors, 1 NE555 timer IC, a relay and few passive components. The circuit is completely automatic which starts the pump motor when the water level in the over head tank goes below a preset level and switches OFF the pump when the water level in the over head tank goes above the full level.

Probe D is positioned at the bottom level of the tank while probes A, B and C are placed at full, half and medium levels of the tank respectively. The level sensing part of the circuit is built around transistors Q1, Q2 and Q3. When water level is below the quarter level probes A, B and C are open and the transistor Q1, Q2 and Q3 remains OFF. When the water level rises and touches the probes the corresponding transistors gets biased and switches ON. Resistors R1, R2, R3 limit the bases current of corresponding transistors while resistors R4, R5, R6 limit their collector current. LEDs D1, D2 and D3 provide a visible indication of the current water level.

When the water level goes below medium, transistor Q2 gets switches OFF and its collector goes positive. Collector of Q2 is connected to the base of transistor Q6 and as result transistor Q6 gets switched ON. Transistor Q5 will be also ON because its base in connected to the collector of Q4 which is presently OFF. As a result when the water level goes below medium relay K1 gets energized and the pump is driven. The relay is wired in the latching mode so that even if the water level goes above medium level the pump remains ON so that the tank gets completely filled. For wiring the relay in latching mode one set  of N/O contacts is used. When relay is activated these contacts close which forms a short across collector and emitter of Q6. This makes the state of Q6 irrelevant to the operation of the relay and the relay remains ON as long as the transistor Q5 is ON. The only way to make the relay OFF is by switching OFF Q5 and it is done automatically when the water level reaches the full level.

Collector of transistor Q1 is connected to the trigger pin (pin2) of IC1. When the water level reaches full level the transistor Q1 gets switched ON. As a result its collector goes to ground level which triggers the IC1 which is wired as a monostable. The output of IC1 goes high for about 1S. This makes the transistor Q4 ON for the same time and transistor Q5 whose base is connected to the collector of Q4 is switched OFF cutting the supply to the relay. This makes the motor OFF and it remains OFF until the water level again goes below the medium level.

Resistor R8 is a pull up resistor for the trigger pin of the NE555. Capacitor C3 couples the collector of Q1 to the trigger pin of NE555 and facilitates edge triggering whenever the transistor Q1 goes ON. A monostable circuit can be made edge triggered by connecting the trigger signal to the trigger input pin through a capacitor. The capacitor blocks DC and passes sudden changes. The circuit used here is termed as negative edge triggered because the monostable is triggered when ever the trigger input signal falls. R10 and R12 limits the collector current of Q4 and Q5 respectively while R9 and R11 limits their base current. R13 limits the base current of Q6 while D4 is a freewheeling diode which protects the switching transistors from voltage transients.

Circuit diagram.


Water level controller circuit diagram
Probe arrangement diagram

The probes can be arranged as shown in the diagram above. Insulated Aluminium wires can be used as the probes. The probes can be binded on a plastic rod and should be erected vertically inside the tank. The length of the probes wires and the supporting plastic rod must be chosen according to the depth of the tank. Since DC is used in the level sensing section electrolysis will occur in the probes and so the probes require small maintenances in 1 or 2 month intervals. Using AC in the sensing section will completely eliminates the chance of electrolysis and I am presently working on such a circuit. You can expect it soon.


  • Use 12V DC for powering the water level controller circuit.
  • The relay I used was a 5V/220 ohm relay and that’s why the current limits resistor R12 was added in the circuit. If you use a 12V relay then the R12 can be shorted.
  • Do not use a relay that consumes 500mA. Maximum collector current PN2222 can handle is 600mA.
  • Use insulated single strand aluminium wires for probe and they can be arranged in the tank as per the probe arrangement diagram.
  • Use a holder for mounting NE555.
  • The circuit can be assembled on a Perf board.
  • K1 must be a double pole relay.
  • The load current, voltage ratings of the relay must be selected according to the ratings of the pump motor.
  • The type number of the transistors used here are not very critical and you can do suitable replacements if any type number is not available.
  • Most of the components required for this project can be found inside your scrap box.

Power supply for this circuit.

12V DC supply
12V DC power supply

A classic 12V regulated DC supply based on 7812 is shown above. A power ON indicator LED is also added in the circuit.Resistor R13 limits the LED current. A small aluminium heatsink can be fitted to the 7812 for better saftey.Small Al heatsinks for TO-220 package are readily available in the market.

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133 Responses to “Water level Controller”

  • Ab says:

    Can you please provide me with a component list and pictures showing this regards.

  • harsha says:

    sir also please tell me where to connect the negative terminal of the battery as it is not shown in the circuit diagram

  • harsha says:

    seetharaman sir can u please tell me what is the use of 1N4007 diode in the circuit???
    what is latching mode of the relay???
    how to wire the relay in latching mode????
    sir please help me out.its very urgent

    • Seetharaman says:

      1N4007 in parallel with the relay to protect the diving element from the back EMF of the relay during switch off. called free wheeling diode. Latching of the relay is sullying the power through its own normally open contact for energising the relay. When relay coil gets an on pulse from the driving element it will switch on and continue to be on through it own NO contact even if the driving element switches off. This is called latching of the relay. to switch off the supply to v\be removed for the next cycle of operation.

  • brij says:

    I tried the circuit, i have second and third led always growing slighty and motor does not run? Can any one advise what could be the problem…. I am using 12 v relay and 12v dc motor.

    • Seetharaman says:

      for 12 volt relay you have to modify this circuit totally. Try to use 5 volt relay to avoid the redesigning problem.

  • prema says:

    i tried this circuit but there is a problem in the output .please i want know basic error caused in the circuit.

  • harsha says:

    well can any one help me out???
    i am using a single phase 18 watt motor.what should be the necessary rating and type of the relay???
    please help me out.its very urgent

  • samiran says:

    Can i use BC546 transistor instead of relay driver Q5 and Q6 PN2222?
    Please help

  • mahendra n says:

    sir i use se555 for this project
    it is equal-ant to ne555 plz quick replay

    thank you

  • Salman Tariq says:

    sir i use kn2222 instead of pn2222but it diddnt work

  • sanzuu says:

    You have made an essencial & important circuit . In my case I just altered probe B & C .Because there is no use of probe C instead of glow LED, water level never goes down below C because if water level goes below B, Pump will automatically turn ON. so here Q3 always on to glow LED only and never turn OFF. If probe C placed above probe B, it will be perfect. I have placed probes in the following sequence A,C,B & D. A at the top (3/3), C at above half (2/3), B at below half (1/3) and D at bottom(0/3).
    Is this Ok?

  • carlo says:

    Sir,can you help me upgrade the circuit. Because there is a time that the motor does not pump water.In that case,there is a possible that the motor be burned.I want to connect a circuit so that when there in no flowing water in the inlet pipe the motor will be automatically turn off after 5 seconds.

  • Viques says:

    @seetharaman can u design a circuit to control power in different rooms.ie,a circuit whereby a landlord can monitor how tenants consume the power and it can trip the supply when a preset amount of current is exceeded?.THINK ABOUT IT..

  • Viques says:

    Who said this water controller doesn’t work?. I made it and its PERFECTO..works fine fine.
    SEETHARAMAN..thanks a lot.

  • Harshal says:

    it worked but if i want to do it for large scale what should i do for that ???

    • seetharaman says:

      Hi you please use float swiches in place of probes, which requires cleaning every alternate months though it is SS.

  • Fashola Oluwatobi. says:

    D project is ok but It as no conclusion part.

  • mark joseph says:

    sir do you have the full component/parts list? if you have plss send it to my email: markjoseph.catane@yahoo.com sir plss reply as soon as possible..thanks!!

  • mark joseph says:

    sir if you have any videos/pictures showing how it works can you also send it to my email:markjoseph.catane@yahoo.com thanks!!

  • mark joseph says:

    sir can you plss tell me all the parts one by one and the total of how may parts? sir plss send it to my email as soon as possible.. thanks in advance!!

  • VIJILAN.V says:

    Good day sir,
    I need circuit diagram for water level controller which should be set in the underground tank which collects the water from the municipal.
    that is when the water level rises and attain a particular stage in the underground tank the motor should be switched on and the water if drain the motor should be set off that’s my requirements sir.
    Thanks in advance.

  • Sudharsan says:

    Can you kindly explain the role of IC555 as it is a timer IC and i dont see any thing that is obviously using a timer related feature..

  • Sudharsan says:

    hi sir,

    I am in process of constructing this circuit for my home. Here you have provided 3 level sensing probes where the middle one just shows that the level of water is above the height of the probe. Now my requirement is to have 5 probes where the first and last for switching OFF and switching ON the motor and remaining 3 LEDs just displays the level of water. Kindly suggest how this circuit can be improved to have that feature.

    Thanks !!

  • Krishna P. says:

    My question is, does this sensor user AC or DC voltage to sense water in the tank?
    If it uses DC voltage will it cause the metal contacts to corrode in water?

    • Seetharaman says:

      Hi Krishna it uses DC only. hence cleaning of electrode is required every month.(use stainless steel electrodes)

  • Amandeep singh says:

    my relay is not cutoff when the water is full in tank.and i have use 8-pin DP 5V relay in ckt. Plzz tell me what can in do.and my motor supply is 220V AC.plzz tell me what can i do ?.help me…
    Quick rply….

    • Seetharaman says:

      Hi singh dip relay contacts are for very low voltage switching current level. it must have got welded. please replace the relay with good quality double pole double throw (DPDT) (two change over contacts) 12volt DC relay with a contact rating of 250 volts 10amps AC. short R12.

  • amandeep singh says:

    can i use BC546 beside BC547 transistor….
    quick reply

  • ABDOULAYE says:

    After going through this piece of work I came to realize that ,it is used for a single reservoir but the case Im having is two reservoirs which are connected separately but controlled by one pump. So how can I modify this circuit satisfy my needs? Thanks

  • ravi kumar says:

    sir what is all resistances wattage thanq

  • hastings says:

    What do i do the pump is runnin continously

  • A.K.S says:

    Hi, sir sitharaman. I want to use this type of water level controller ckt for water well not in tank. Can i use same ckt in this case when water is ful then pump is on and when water is finished then pump is off.
    Plz reply me sir that is important.

  • Jagannadh says:

    well,sir thank you for the circuit…and sir, can u please suggest me the modifications that are to be done in the circuit so that i can use it for different rating loads like 0.5hp, 1hp,2hp…5 hp. kindly help me sir as i am in need of these circuits. -Jagannadh.jagannath.girish@gmail.com

  • Naresh says:

    I tried this circuit, there is some error in this. When 12V (batteries) is given to the circuit, middle LED is always glow even other LEDs are glow. Relay is not working, I use 12V DP 8pin relay. Anything wrong in this ckt, help me anyone……….

  • Naresh says:

    I tried this circuit. But relay is not working and second LED is always glow even other Led is glow. The 12V 8pin relay is not working I use 12V Dc (batteries) as supply. Is anything wrong in ckt. plz help me…..

  • uttam says:

    how relay on
    and off i dont understand..pls tell me

  • NITIN says:

    what should be relay rating for 3 phase 5 hp motor

  • rohith bv says:

    sir what is the relay rating?

  • NITIN says:

    what should be the rating of relay for 3 phase motor

  • M.P.Saini says:

    Looks like good & cheapest circuit, I will make it for home.
    & Waiting for Water level controller using AC in Sensing section.
    Pl.send me the circuit using A/C sensing prob

  • priyanka says:

    I want to know, how to make probe connections with the water tank in the water controller circuit……

  • Jaisin jacob says:

    Sir in led tourch using MAX660 the ic is not avalable in our area.can you prefer an suitable another ic.plz.

  • Tittu Thomas says:

    Nice, I will try this…..



  • deduke says:

    Hi i have chosen this to be my project work with small modifications of adding 7 seg. display to the transistor Q1& Q2 through transistors in series to them. can you help with this.
    i think this circuit is just fine for domestic water control systems . i want to know if there are any other likely faults, that may present itself in the process of building the circuit.
    i will be happy in you can help.

  • Basha says:

    I tried the circuit, i have second and third led always growing slighty and motor does not run? Can any one advise what could be the problem…. I am using 12 v relay and 12v dc motor.

  • Seetharaman says:

    Hi The relay is 12 volt 50 to 100mA coil with 2 pole change over contacts of 250volt @ 10 to 15 amps rating for any single phase 1 to 1.5HP motors

  • ahmad abubaker says:

    that’s really grade
    but can you help me i wnt to do this project but can you tell what is the equipment that i need and the program and the code to do it and explenation ? here is my email : ahmadmahmud18@hotmail.com

  • Mohammed says:

    Thanks for the circuit. I used wanted to know if we can use same with 220V single phase motor pump. What will be the relay rating and what other changes required to be done in the circuit. Thanks.

    • rohin says:

      hi brother,relay is like a switch it can on and off all electric product.for i hp single phase motor relay should be minimum of 10amp.this circuit is made for 220v moter. neutral point will go direct to motor and phase will go through relay.

      • Mohammed says:

        Thanks Rohin for reply. In the notes, it is said that the PN2222 can handle 600mA max. How can i use replay of 10amp or more??

  • Aman says:

    Dear sir,
    what type of pump controlled by this Circuit?

    please tell me about the pump ratting.

    is it possible to controlled a DC 12 V Water Pump.

  • Ruben says:

    How was those resistor were selected? What current values were used to calculate them?

    Base: R1,R2&R3
    Collector: R4,R5&R6

  • saisurya says:

    by mistake i’ve commented at water level indicator
    ther ihave suggested a method and circuit

  • him kafle says:

    hello sir, i have a problem to connect the relay switch.how to connect the relay switch on this circuit?can i connect 5 pin single phase relay on this circuit and how? thankyou.

    • rohin says:

      hi him kafle,you can use only 8 pin relay which call double poll relay.you are using single poll relay which have 5 pin.in this circuit a double poll relay is required.which have 8 pin.two pin are for coil 12vdc and rest pins are two com and two nc and two no point .you have to use only commen and no pin in this circuit.check with multimeter. one side is holding the relay and other side is for motor to switch on.

  • purnendu says:

    plzz send me project Report and program code for 8051 microcontroller based water level controller

  • pradeep says:

    please sent me how to do it

  • ruben says:

    Why aluminum wire? Do you know how much does this wires conduct to turn the transistor on?

  • Anu says:

    Can i please get pcb layou. Kindly sent it 2 ma id.
    Tnk u.
    May god bless you

  • Seetharaman says:

    Hi Shawn go through my earlier comments
    September 19, 2011 at 1:42 pm
    Hi Ravi Both probes C and A to be interchanged. C is just to say the electronics is OK with D3 comming on (to indicate also the tank circuit is also healthy and level is minimum). Now read the above description you can understand better. Q2 will start the pumpamd Q1 will stop the pump. Q3 is only for indication nothing to do with automation.

  • Raheem says:

    Good afternoon sir
    Please sir, I need you to send me a full detail of this project as soon as possible. It is very urgent.
    Thanks for your assistance sir.

  • Shawn says:

    Hi there i think there is a problem with this circuit in terms of explanation how Q1 will be switched ON when the water reaches full level first of all where Q1 is a low level probe … in the explanation it is say ing that “the Collector of transistor Q1 is connected to the trigger pin (pin2) of IC1. When the water level reaches full level the transistor Q1 gets switched ON.” As far as i am seeing Q3 will be switched ON when the water reaches full level it will be biased which is probe C .

  • Seetharaman says:

    Hi Pramod
    You can make your own probe by using 1/18 insulated aluminum cable with end exposed for 10 to 20mm to sense water. The probe arranging diagram indicates that clearly.

  • Lokesh says:


    Looks like good & cheapest circuit, I will make it for home.

    & Waiting for Water level controller using AC in Sencing section.

    Thanks again Lokesh

  • Pramod says:


    Can any one tell me how to make electrode Probe for water level sensing.
    or is there any electrode probes available in market?


  • Kailash Dhakar says:

    How can I use a LED or some other light on the place of DP relay (K1) to just check the circuit that its working or not. Also can I use a 12 V Battery directly as power supply?

  • Sriram says:

    Pls sent the pcb circuit

  • wasim says:

    plz give me the pcb layout of that circuit. its urgent.

  • shashank awasthi. says:

    sir plz send me full detailed project report on my mail id. it is very important and urjent. plz send as soon as possible.

  • dinesh says:

    hi i want to make this circuit. please sent me PCB layout on my above email address
    pls send any single prob sens level circuits

  • Seetharaman says:

    Hi Hari you can do, if you know how to activate the reed switch with raising or lowering of water level.

  • Hari says:

    Can i use reed switches in place of submerged aluminum senor rods

  • danish says:

    i want to make this circuit. please sent me PCB layout on my above email address

  • Seetharaman says:

    Hi Tony DP relay is the requirement. The circuit cannot directly drive mains voltage driven AC motors.

  • tony says:

    sir, kindly mail me the details of project… can i use sp relay in place of dp relay???? is it possible to short the relay and connect the motor directly to the circuit.. pls reply as soon as possible..

  • nadeem says:

    i want to make this circuit. please sent me PCB layout on my above email address


  • Samuel says:

    can you please send me the full project report of this ciruit..please its VERY urgent please.

  • ADNAN SHARIF says:

    very good project, i made this, its working…

    • duke daniels says:

      hi if it worked for you can u send me the pictures and arrangements on the bread board.
      i believe in this work that it works.
      my email is

  • Seetharaman says:

    Hi Sameer see my comment dated 19th September identify the probes and connect the probes as suggested.

  • sameer says:

    can you please send me the full project report of this ciruit..please its very urgent please.

  • rosil says:

    ,is it that the switch is applicable for this project in detecting water level?rply asap..please..

  • raj says:

    hi, thank you , recently i cleaned my sump by disconecting the sensor wires but i forgot remeber the code , there four wire from the unit such as white two . orange and blue , the follwoing connection where attemmed b

    white – 2nos – conected to lower sensor i the sump
    blue – 1no – conecceted tp meddle sensor in the sump
    oreange -1no – connected to upper sensor in the sump, kindly me at the earliest , please.

  • zacmoron says:

    can u pls send me the full project

  • sedaghatimilad says:

    I want to assemle this circuit, can you send me The full project

  • kayode says:

    My hnd electronics tutor is not finding this circuit normal
    We tried simulations, and built. Pls,it is not working as it should.
    Do you have any improved method.
    Thanks awaiting response.

  • Pavithra says:

    hi wer to give the point P of the relay and N of pump plz reply……..

  • Pavithra says:

    could plz give information in detail abt how the transistor is turned on/off by sensing probes

  • bola says:

    Sir i have designn the circuit it does o n the relay but it does not off when the water gets to the full level…..i need your help on what to do pls.i have confirm the the timer IC legs numberes

  • bola says:

    Hi,my coment is simple is just that i have design this circuit it works by switching on the relay which you said we could either use 5v or 12vdc.the problem i encounter here is that when the water reach the full level in the tank instead to off the pump is still pumping the water every where is been flooded….i built this project as you instruct…
    pls i need to know the polarity of the IC NE555 kindly send me the legs number pls i need a details that can make the pump off..

  • yun says:

    hi expert…
    may i know how to create the circuit to send the signal through wireless?is there any need for us to add the antenna in the circuit?
    has anyone have a n experience to build a water leakage wireless sensor circuit before?really appreciate if anyone can share any information regarding this problem…

  • Seetharaman says:

    Hi Akila please read my comments dated september 19th.

  • Akila says:

    your circuits diagram are incorrect.

    brainless cow,because of you my water tank is empty and my Water pump exploded.

    • jojo says:

      Akila, Did you verify the connections? Please check your circuit arrangement as many people has assembled this correctly.

  • N.Mahendran says:

    Very like

  • ADLIN says:

    I attempted to do a circuit design from electronics for you magazine on liquid level alarm but i couldn succeed please say me few things to take care while desingning circuit

  • saber says:

    لطفا مقاله کامل برای پرزه دانشگاهی جهت این مدار نیاز دارم برایم ایمیل کنید مدار فوق را بسیار جالب طراحی کرده اید متشکرم

    Please complete for parts of articles to this circuit, I need you to email me a very interesting circuit design.

  • yimam says:

    can you give the full project report paper please help me!

  • mahipal kumawat says:

    sir,what would be the length of probes for a 4m long tank.. plzzzzzz do reply

  • ayyanar says:

    please tell me brief content

  • Debashis Pattanayak says:

    i want full informatatoin on this project.Because i am doing this project.pls.

  • abhishek says:

    Fantastic project for science exhibition but not for real life as it is not corosion resistant. I am using it for my exhibition of class 9.

  • PATRICK says:

    Sir is it normal to have all LED’s lighten up even without contact with D, I’d noticed that LEDs are already on even though water is still empty, it just brightens up when probes contacts with water

  • jaimin says:

    dear seetharaman,

    please let me know i want to put one bypass switch then what i have to do ..

  • thomas says:

    hi sir! I just want to know that if I make a demo model using this circuit, and the height of lifting water is 8ft, then what is the specificationof the pump and relay???
    Sir do reply please.

  • seetharaman says:

    Hi Ravi Both probes C and A to be interchanged. C is just to say the electronics is OK with D3 comming on (to indicate also the tank circuit is also healthy and level is minimum). Now read the above description you can understand better. Q2 will start the pumpamd Q1 will stop the pump. Q3 is only for indication nothing to do with automation.

  • seetharaman says:

    Hi Ravi and Milton try this simple circuit. instead of using tank as a probe add one more proble be at the lower most level, touching almost bottom of the tank.

  • milton watts says:

    i have gone through the procedures for the water level control and started constructing one. what is the theory underlying the action of this circuit?

  • RAVI says:

    I don’t understand the concept of realy wil you please tel me the information and the working principle in this circuit i am waiting for your reply
    thankfull to you sir

  • dipesh says:

    in my circuit the relay either gets closed or opened without automations. and the power suplly voltage drops drastically . what should i do?

  • venkatesh says:

    very use the constant 12v dc supply application

  • Martin says:

    Have got the AC probes designed and working yet?

    You mentioned that, Using AC in the sensing section will completely eliminates the chance of electrolysis and I am presently working on such a circuit. You can expect it soon.

  • SEBIN JACOB says:

    this circuit is god but.what about dry run of motor?

  • JAHFARALI says:

    Yes I am also make one like this using float…it is semi automatic…..not fully automatic..It will switch off pump automatically need to make fully automatic How…????? and also need low voltage cutoff other wise it will damage water pump..

  • G P Koruthu says:

    I am using a float on a vertical aluminium rod with two 4″ diameter aluminium discs (one for the upper limit and the lower one around one foot below).A mechanical switch with a lever (a kind of ‘limit switch’)is placed in between.When the water level goes down, the foat and discs go down. when the lower disc touches and pushes the switch lever,the switch turns ON and the pump starts.When the water level goes up, the float and the disc assembly goes up until the top disc pushes up the switch lever making the switch OFF and thereby the pump. I am using the mechanism for many years without any problem so far.Only thing is that we have to protect the switch from rain and hot sun.

  • JAHFARALI says:

    Good circuit, But need change or clean the level sensing conductor frequently..It is directly contact with water.. It is a demerit of this kind of Water level controller….please publish a water level controller with float…

    • Sid says:

      the ckt before 555 ic,is working only connect spdt 5 pin relay with it and motor the ckt works the i,c annd and rest of the ckt after it doesn’t works.