Underground Water Pump Motor Dry Run Protector Without Probes

The circuit idea presented here shows a simple method by which  insufficient water conditions inside an underground tank can be sensed without introducing probes inside the underground tank, and thus preventing any possibility of motor dry running. The circuit also incorporates an overhead water overflow control feature. The idea was requested by one of the interested readers of this blog.

Technical Specifications

Do you have any idea of how to sense dry run motor by checking at the overhead tank inlet without checking at the underground tank since it takes more work in getting the wire from underground to motor place.

My requirement is motor should go off if no water is flowing at the tank inlet. Also motor should not off initially since it will take at least 5 seconds to push the water at the tank inlet.

My requirement is to switch off the motor when motor is not able to pump the water. This may be due to water level become less than certain threshold in the underground tank Or pump has malfunction.

My preference is not linking any wire from the underground tank to the circuit. My preference would be sensing the water flow in the overhead tank inlet. Hope you understood my requirement.

I would like to switch on the motor manually. If we replace the buzzer with a relay, then motor will be switched off immediately upon switching on motor,since it will few seconds for water to flow on the tank inlet.

We need to provide some time delay to sense the water flow at the tank inlet to avoid this problem. but I am not sure how to introduce a delay. Please help me on this.


The Design

The circuit of the proposed underground water pump motor dry run protector can be understood with the help of the following details:

The circuit is powered with a 12V AC/DC adapter.

When the push-button is pressed momentarily, the BC547 transistor along with the BC557 relay driver stage is switched ON.

The 470uF capacitor and the 1M resistor forms a time delay network and locks the entire relay driver stage for some predetermined delay after the push button is released.

This delay interval can be adjusted by experimenting with the 470uF capacitor and/or the 1M resistor.

As soon as the relay activates, the motor is switched ON which instantly starts pulling water in the overhead tank.

The moment water inside the overhead tank pipe connects with its residual water, the submerged probe which is the positive probe gets linked with the probe that's introduced at the mouth of the pipe. This enables voltage from the lower probe to reach the base of the relevant BC547 transistor via the water, and the 1K resistor.

The above action now latches the relay driver stage such that even after the time delay lapses, the relay holds and sustains the operation.

Now the motor halts only under two conditions:

1) If the water level reaches the overflowing level of the overhead tank wherein the positive potential from the lower probe gets connected with the probe that's connected with the base of the upper BC547 transistor.

The condition switches ON the upper BC547 which instantly breaks the relay driver stage latch and the motor stops.

2) If the water inside the underground tank dries out, which obviously stops the water link inside the overhead tank pipe and breaks the relay driver latch.

An Automatic version of the above sump motor controller with dry run protection system may be witnessed below:



A fully automatic version can be also built using 6 NOT gates from the IC 4049 as shown below, this configuration can be expected to work much more accurately than the above transistorized version of the automatic underground submersible water pump dry run protection circuit.

CMOS tank overflow control with dry run sensing


Feedback from Mr. Prashant Zingade

Hello Swagatam,

How are you? Your Idea and logic are awesome. hats-off to you. I tried IC4049 version, It is working fine except one issue.(I done one modification base on your previous design and it is working now).

I am facing one issue in IC version like when we put it on auto mode, dry run function is not working. Please see attached simulated video file.

Case 1: I observe If water level reach below bottom level relay will on pump but it fail to sense dry run and pump will continue to on.

Case 2: In manual operation it works perfectly. Excuse for any typo.

Warm Regard

Prashant P Zingade

Solving the Circuit Problem

Hello Prashant,

Yes you are right.

To correct the situation we will need to connect the output of N6 to the base of the BC547 through a capacitor, you can try connecting a 10uF here.

Negative of the capacitor will go towards the base.

But the problem is, this operation will activate the system only once, and if water is not detected then the system will switch OFF the relay and remain switched OFF permanently until it is activated manually using the switch, and until the yellow sensor comes in contact with water yet again. Regards.


Simple Dry Run Protection for Motor

The following diagram shows yet another effective dry run protection that can be added to the pump motor, in cases where water is unavailable in the tank and no water flows out from the pipe outlet.

Here the push-button is initially pressed to start the motor.

The 1000uF capacitor and the 56k resistor acts like a delay off timer and keeps the transistor switch ON even after the push button is released so that the motor keeps running for a few seconds.

During this time water can be expected to flow out from the pipe outlet, and this will fill up the small container introduced near the mouth of the hose pipe. This container can be seen having a float magnet and a reed switch relay arranged inside.

As soon as water starts filling inside the container the float magnet quickly rises at the top and reaches at a close proximity to  the reed relay, latching it ON. The reed relay now feeds a positive voltage to the base of the transistor ensuring that the transistor gets latched up and keeps the motor running.

However in an absence of water, the reed relay feedback is unable to turn ON, which causes the motor to shut down once the delay OFF time elapses after the predetermined amount of delay.

simple motor dry run circuit

Need Help? Please send your queries through Comments for quick replies! And please Bookmark my site :)


Swagatam said…
You are welcome! I have updated the data, please check it.
Swagatam said…
water produces a high resistance to voltage, so no chance of any short circuit.
Swagatam said…
The probe which is submerged at the bottom can be put next to the probe situated near the pipe outlet, this will rectify all issues.

Furthermore a 100uf capacitor may be added across base of BC557 and positive for avoiding relay break under interrupted water flow conditions from the pipe.
Soon said…
Hi Swagatam
I Follow Ur blog last 6 month and i like
I request u can u make a Water activated relay with 12 volt dc and 12 volt relay
Simple when tank full the relay activated
Swagatam said…
Thanks Soon,

You can make a relay driver circuit as shown in the following link (with some modification), and use the transistor base resistor free end and the positive supply as the two sensors placed just at the brim of the tank. The two terminals must not touch each other rather put close by such that they get bridged by the water just before over flowing, this will instantly activate the relay


The base resistor can be a 1K.

Remember to use a Darlington paired transistors (two BC547 put in Darington form)
Swagatam said…
I have suggested the easiest possible method, 555 will be a complex circuit.
soon said…
Hi sir

plz send me the circuit diagram of water activated relay 12 volt

plzzzz help sir

my email id - gadgetidea@gmail.com

Swagatam said…
Hi Prabir,

Building it could be a lot time consuming and expensive, I would suggest that you buy LED strip or LED ribbon light of different colors and power them from any AC to DC adapter, that would be quick and simple.

you can see the image here:


Swagatam said…
that's highly unlikely, unless there's something leaking into the base of the BC547.

you can try the following:

remove the capacitor entirely and then check....or alternatively connect the emitter of the BC547 through a 3V zener diode. anode will connect with ground and cathode with the emitter.
Swagatam said…
that means either your transistor is faulty, the connections are wrong or could be some other fault.

3v zener will prevent leakage current from entering the base of BC547 until it exceeds 3v which can never happen unless a legitimate 3v is applied.

no pull-down resistor is required.
Sriram Kp said…
Hello sir, In this same circuite, how to add the connection like if the water in the OHT is low means the motor have to start automatically? pls send the circuit diagram to my id. sriramsrikp@gmail.com
Swagatam said…
Sriram, if possible i'll surely send it to you.
Sriram Kp said…
Am in first floor. the tank is on 4th floor. so the distance betweent the probes in the tank and the circuit in my floor is 15-18 meters. wil the circuit work correctly???
Swagatam said…
you will need to place the circuit right beside the tank, otherwise it could create problems and incorrect results.
siddu said…
Hi sir
that circuit what is the minimum distance between from circuit to tank
Swagatam said…
Hi siddu, it shouldn't be too long not more than 5 meters.
Harun Rashid said…
Hello sir,
I am Harun, Sir i want a automatic water level controller circuit for submersible / underground pumps use. Please send the circuit at: harunuvtsvharun@gmail.com
Swagatam said…
Hello Harun, one example circuit is already presented in the above page, if you have any other specifications please provide a detailed explanation for the same.
Ajo Anto said…
Is here a possibility to eliminate the 557 pnp as the relay driver and to make use of buffer of bc 547 ??
Swagatam said…
use two BC547 in Darlington mode and connect the relay in place of the collector 10k, this will allow you to remove the BC557 and its base resistor.
Vamsi Krishna said…
Hello sir, my name is vamsi. can u pls suggest me, In this same circuit, how to add the connection like if the water in the over head tank is low, the motor have to start automatically that means i need it to work as Fully automatic.can u pls send me the circuit diagram. my id. login2vamsi183@gmail.com.
Vamsi Krishna said…
Hello sir, i'm an electronics hobbyist. sir can u pls suggest me, In this same circuit, how to add the connection like if the water in the over head tank is low, the motor have to start automatically. that means i need it to works as fullyautomatic pls send the circuit diagram to my id. login2vamsi183@gmail.com. awaiting for ur needful reply. thank u...
Swagatam said…
Hello Vamsi, you can make the following circuit:


and try connecting its relay contacts in parallel with the above circuit's relay contacts.
Unknown said…
Hi Sir,
Can you plz guide me. I wish to installing this circuit in my house automatic water level controller containing NE555 & CD4049 (simple water level controller) I wish to combine this circuit. would it work? And how to install its probes in OHT.
Swagatam said…
I'll try to help you...
Swagatam said…
you'll need to fabricate the probes as shown in the diagram..
Vamsi Krishna said…
Dear sir,
i tried as u said. the differences of both the above given circuit is its sensors are connected to OHT. and which you said circuit is for, the sensors to connect to under ground tank. but actually what i need is., to the same above given circuit can you pls design with automatically starting also...THANKS
Swagatam said…
Dear Vamsi,

this circuit is fully automatic and is exactly as required by you:

Vamsi Krishna said…
Dear sir,
in the same above circuit all i need is to work as fully automatic. the above design is semi automatic (manual start and auto cut off with dry dun) But can u pls design with adding auto start feature..? because our sump ( under ground tank ) is completely closed and tiled. and can not drop the sensors in it. so i think the above design is better putting sensors in OHT.so, kindly can u pls modify as per the request....
Swagatam said…
Dear Vamsi, I'll try to do it, and let you know....
Vamsi Krishna said…
Dear Sir,
Thanks for the response again. i'm sorry that i confused u. the design u posted for the bore well is very useful to me. but my request is the above circuit also for my sump motor purpose. so the modification i need about it like to work as fully automatic.thanks.
Swagatam said…
Dear Vamsi, yes I understand, thanks, I'll try to do it soon..
Swagatam said…
...please check out the new diagram
Vamsi Krishna said…
Dear Sir,
Thank you very much. i'll always be in touch with u regularly to discuss about more circuits designs..ill be back again after i prepared the circuit. THANK YOU VERY MUCH again.
Vamsi Krishna said…
what are the codes of three diodes 1N4007...? or IN4148 Zener.....? in the given new diagram.
Swagatam said…
You are welcome, Vamsi
Swagatam said…
for the relay it's 1N4007, remaining can be all 1N4148
Vamsi Krishna said…
dear sir,
the above given new circuit is also not working. as the same way i connected all the components through marking and checking thoroughly. can please check practically, or shell i change any values in the circuit...? Thanks..
Swagatam said…
Dear Vamsi, just by connecting everything correctly will not necessarily make a circuit work. It might require many adjustments and tweaking.

all these circuits are for those who know electronics very well and have plenty of practical experience.

so you'll have to first learn how the transistors are supposed to functions, then build and confirm the stages step wise and only then finally you may be able to finish it successfully...it could be many long tutorial sessions for you....

Vamsi Krishna said…
Thanks for the reply Sir......:)
Rahul Singh said…
what if the same motor is used for irrigation ie there is no any overhead tank and a rubber pipe is inserted in water pump mouth then how to detect if motor is running dry or not
Swagatam said…
Rahul, you will need to place the sensor probes at the mouth of the pump pipe....as long as water is coming out from here, the circuit will stay switched ON, but the moment the pump stops throwing water, the pump will be switched off....preventing its dry run
Swagatam said…
check carefully, you will find it at extreme left of the design
I have seen the blog "An Automatic version of sump motor controller with dry run protection system" in https://homemade-circuits.com/2013/07/underground-water-pump-motor-dry-run.html
Can we put a switch in the circuit to run motor at any time in manual mode (water may not reach low level) and auto stop motor when tank is full.
Hope you understand & Thanks
Pls. reply: amarendra_co@yahoo.com
Swagatam said…
Amarendra, you will have to momentraily cut the 12V supply which goes to the upper tank in order to initiate the motor...this can be done by a push-to-OFF kind of switch connected in series with this 12V line.

but please note that this circuit will need to be perfectly optimized in order to make it respond to the various water linked sensors...otherwise you may find it difficult to get the expedited resulst from it.
I tried on simulator software. It start on push button. But it is not stoping replay when water touch to probe.

Any advise or troubleshooting?
Also if possible I will upload simulator video on YouTube and share link.
Swagatam said…
which probes are you referring to?
the one which is at the left just under the overhead tap is for latching the relay.....the latch will continue to hold until the water has filled upto the brim of the tank and until the right side probe comes in contact with water, then the latch will break.

on the other hand in absence of water the relay will not be able to hold for more than a few seconds and the latch will break due to no water reaching the left side probes, and the motor will be stopped ...

this is how the dry run protection is implemented.
Yes I got you. Latch is break even after water touch brim of tank .
If I'm not wrong top most bc547 will break latch. But in my case it is not breaking latch.
Swagatam said…
when the tank becomes full, the positive supply comes in contact with the upper BC547 base, that triggers the BC547 and this in turn grounds the lower BC547 base...causing the relay to deactivate. this situation stops the motor and breaks the latch by stopping the water flow to the tank

the simulation is simple and will work only if the water bridging across the sensor points are good.

you can try a Dralington pair for the upper BC547 to increase its sensitivity.
Dmu said…
Sir,Fully Automatic version circuit is not working,i tryed 11 times on 6 boards,if any modification in this circuit please tell me sir,How to solve it? Thank you
Swagatam said…
Dimu, it will not work unless you confirm and optimize each stage separately on table using sample water in a small container to simulate tank water,and then integrate each of the stages one by one for the final outcome....

Since it is a transistorized circuit it might be be little inefficient and require some serious tweaking to make it work perfectly.....

if possible I'll try to update an IC version of the same which will not require much adjustments and can be made to function quickly...
Dmu said…
Sir,Thank you for your reply, I am waiting for you to send the IC version circuit soon.
Swagatam said…
sure...It might take a little time so kindly bear with me...
Swagatam said…
I have updated it in the article, you can check it out
Dear Sir,

Wish you a very HAPPY NEW YEAR sir, Stay happy always......

Sir if possible can you please give this circuit with fully assembled in Bread Board ( practically) please, as I'm beginner I can understand in that easily.

Thanks & Best Regards
PG Ragavandir
my Email-ID is vijayragavandir@gmail.com
Swagatam said…
Thank you Ragavan, Wish you too a Very Happy New Year!!

I am sorry due to lack of time practical guidance may not be possible, however if you any specific queries I can help you to solve it here
Dear sir,

Thanks for your reply, I tried doing first and second circuit but I failed, so only I asked you for bread board model. (I can understand you will be busy sir so only I requested if possible.) I Will try sir. So kind of you sir.

Best Regards
PG Ragavandir
Swagatam said…
Thanks Ragavan, it is your learning phase, so you may have to go through some failures, all do...I am sure soon you will be able to overcome the failures and begin succeeding with the projects. all the best to you
Dear Sir,

Thanks for your positive words and faith on me.

Soon will overcome sir.

Thanks & Best Regards
PG Ragavandir
Its regarding IC version.
If it is fully Automatic(i mean to say pump will when water level go below low level and stop at high level) then why push button is used.
Correct me if I am wrong.
Swagatam said…
the push button start is an added feature which allows the user to start the motor anytime he wants, without depending on the lower level detection.
Thanks, I will try this.
One more quick question. How this IC version to be used in submersible pump. (There is stop and start button on board)
One quick question. Can we use IC version with submersible pump. If yes then how , what are changes need to be done.
Submersible control unit have RED and GREEN button. Green use to start pump and red used to stop. In such case where to fit circuit.
Swagatam said…
for start stop contactor operations, you may have to employ the following concept


or the following

Swagatam said…
I have answered your question, please refer to the previous comment....
I am talking about IC version.
1)What is value of cap connected to emitter of BC547 (OR positioned to left of N3).
2)Please correct me if im reading circuit wrongly . From circuit diagram I think N1 and N2 (pin 1 &2), N3 and N4 (Pin 3 & 4) connected to each other ?Right
Yesterday I build and install transistor based circuit. I am facing some issue. When water touch to wire (or Sensor) water pump misbehaving, it stop and start constantly (In short fluctuate constantly), also my mother notice that pump start and stop automatically. Please advise.
Swagatam said…
for the transistor version you will have to understand each stage and troubleshoot it yourself, it would be impossible for me to do it from here since there are many stages which may need careful adjustments.

by the way in the above comments you said you wanted to build the IC version and you also said you wanted star/stop type of control for your motor, so I am a little confused.
Swagatam said…
the cap value is for the delay effect when the push button is used...it will need to be experimented, it could be around 22uF to 47uF

input of one gate is connected with the output of the other gate for N1/N2, N3/N4
Thanks for you comment.
Can I try to increase value to cap of BC547(used to break latch/ used In OHT)

Just few day before I saw IC version. Previously I was working on transistor version, It is done now. I will try for IC version and let you know if any issue.

Can I have your Email ID ? so that I can share circuit diagram from which I created PCB
I'm taking about first circuit diagram. 3 transistor used.
Swagatam said…
OK but you cannot control a start/stop contactor box using the first circuit?

my email is

Swagatam said…
if you increase the timing capacitor that might affect the dry run protection in case water is not available....because with increased delay the motor would keep operating for longer period of time before switching OFF
Dear Sir,

Please check your mail, I implemented that IC circuit and mail photos in the given ID, Please have a look sir and tell me the corrections.

Thanks & Best Regards
P G Ragavandir
Swagatam said…
Dear Ragavan, that would be impossible to check and implement...you must do it stage wise....first build only N3/N4, by connecting the associated parts along with the relay driver and the push switch stage.

once this is confirmed then go for the other gates one after the other and test them with sample water inside a cup...

so it has to be done in this way....and preferably do it on a veroboard not on bread board, because breadboard can be to messy and difficult to troubleshoot the connections.
Dear Sir,

Thanks for your reply, will do as you said sir

Best Regards
PG Ragavandir
Ian Clarke said…
I have just come across this site with these circuits and wonder if you can help me..... I have a similar requirement.
I need a circuit to prevent a submersible bore pump (1100W) running dry, ie exhausting its water supply. I need the pump to shut off when the water level reaches about 1M above the pump intake, and start up again when the water level reaches about 3M above the intake. The pump body at earth potential would provide the common reference. The probes and associated wiring to the surface are already in place at those distances.
Any help you can give would be much appreciated. I can build circuits but just do not have the knowledge to figure the actual circuitry out. Many thanks in anticipation.
Swag said…
I'll design it soon for you and let you know....
Swag said…
I have posted the idea at the bottom of this post

Mansoor said…
I need a dry run protection system for a submersible deep well pump that works by sensing the flow of water through the outlet pipe of the pump. I mean to say the circuit should be based on flow-sensor, and turns the pump off as soon as it detects that the flow of water has stopped. I do not want the system to be based on level sensors or probes. I simply need to turn the pump off when the flow sensor that is installed at any point on the outlet pipe of the pump, senses that there is no flow.
Swag said…
You can try the following concept:


ignore the probe and the connections.

use a small motor with propellers as the flow sensors, connect the motor wires across the 1K end and ground line of the circuit
Mansoor said…
after turning the pump on, the water takes few seconds to start flowing through the pipe. how would the transistor TIP122 be in ON state during that time? also, can you tell any other way, besides using a small motor with propellers, to sense the flow of water?
Swag said…
a reed and magnet arrangement can be used instead of motor,I will try to update the drawing soon.
Mansoor said…
ok. also please tell how the transistor would be in ON state at pump startup
Swag said…
I have updated the diagram in the above article

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