Introduction: The Eco-Shower: How to Cut Your Water Bill If You Have a Teenage Daughter

Picture of The Eco-Shower: How to Cut Your Water Bill If You Have a Teenage Daughter

The Eco-Shower:
My 13 year old daughter does love a good shower.
She REALLY loves one, up to the point where she has been spending up to two hours in the bathroom.
We suspect that she has been turning the bathroom into her own personal sauna.
The result of which is that the rest of the household are having to have very quick, very cold showers unless we keep the boiler on all evening.
We've recently had a water meter installed and our bill has trippled, not to mention our gas bill has rocketed.
Now, you can't reason with a teenage girl and expect a happy outcome where washing is concerned, so another solution was required, and I do like a good problem.

Our shower requires a pump for it to produce enough pressure to be useable.
The pump is housed by the hot water tank in the airing cupboard in my sons bedroom.
I had recently bought my son an Arduino and a pile of sensors to play about with. All this was fun, but we needed a worthy project to put it all to good use.

After a week of consecutive cold showers, I had a Eureka moment!
What if We were to strap a temperature sensor to the hot pipe and use it to trigger a timer on the Arudino when it reached say 40 degrees (centigrade).
Then once the timer has run its course, it triggered a relay that cut the power to the shower pump.
The relay remains switched until the hot water pipe falls below the threshold temperature, at which time the process repeats itself.
The beautiful simplicity is that the off-time is wholely dependent on the cooling of the pipe.
The relay is only activated for the period when the timer has finished, and the hot pipe is above the threshold temperature.
To bypass the "Eco-Shower" as we like to call it can be done by cutting the power to the Arduino.

There have been a few additions we have made to it since the proof of concept.
It now has two pots, one to set the threshold temperature, and the second to set the timer period (or the amount of time the shower runs for before it turns into a pathetic dribble).
There's also a green led that comes on when the temperature sensor has reached the threshold and the timer is running, and a red one when the relay cuts the power to the pump.

We've had this running for about three months now and had a great deal of fun with it.
My daughter gets out of the shower without a word said after 15 minutes, like clockwork every day, and we all have hot showers.
I am anticipating a marked drop in our gas and water bills.
I still have the problem of trying to get my son in the shower for more than a minute, but I guess that's going to require a different approach.

Step 1: ​Parts List:

1x Arduino Uno (ATmega Version Board 328P UNO R3 ATmega16U2 & Free USB Cable for Arduino DE) £5.97
1x DS18B20 temperature module (DS18B20 Module DS18B20 Temperature Measurement Sensor Module TN2F) £1.29
1x red led
1x green led
2x 10KA (linear taper) potentiometers & knobs
2x 330R 1/4W resistors
1x 4K7 1/4W resistor
1x project case
7/02 project wire - various colours

Step 2: The Wiring:

Picture of The Wiring:

Step 3: The Code:

// Eco-Shower Arduino code
// Julian Arnott & James Arnott 2014
// We're using the DS18B20 temperature sensor mounted on the hot water pipe for the shower to trigger a 20 minute timer.
// Once the timer has run its course, it switches the relays that cut the power to the shower pump.
// While the temperature of the pipe exceeds the trigger temperature, the relays will stay switched
// Could add pots so parent can adjust the switching temperature and the shower time.
// switching temperature between 20 and 80 degrees use A0 (pin 23)
// shower time between 5 and 40 minutes use A1 (pin 24)
#define ONE_WIRE_BUS 3 // Data wire is plugged into pin 3 on the Arduino
OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices
DallasTemperature sensors(&oneWire); // Pass our oneWire reference to Dallas Temperature.
// Assign the addresses of your 1-Wire temp sensors.
// See the tutorial on how to obtain these addresses:
DeviceAddress Thermometer = { 0x28, 0x16, 0xA3, 0x84, 0x04, 0x00, 0x00, 0xC3 };
float tempC;
int ledRED = 5; // pin D5 for the led1
int ledGREEN = 6; // pin D6 for the led2
int relay1 = 7; // pin D7 for the relay1
int relay2 = 8; // pin D8 for the relay2
int tempPot = 0; // connect the 10K A taper (linear) temperature potentiometer to Analog input A0
int timePot = 1; // connect the 10K A taper timer (linear) potentiometer to Analog input A1
int temperature_set;
int temperature_read;
int time_set;
int time_read;
int hasBeenSet = 0;
int delaytimer = 0;
void setup(void)
analogReference(EXTERNAL); // Tell Arduino to use the Aref pin for the Analog voltage, (5v)
Serial.begin(9600); // start serial port
sensors.begin(); // Start up the library
sensors.setResolution(Thermometer, 10); // set the resolution to 10 bit (good enough?)
pinMode(ledRED, OUTPUT); // set the red led pin (5) as an output
pinMode(ledGREEN, OUTPUT); // set the green led pin (6) as an output
pinMode(relay1, OUTPUT); // set the relay pin (7) as an output
pinMode(relay2, OUTPUT); // set the relay pin (8) as an output

digitalWrite(ledRED, LOW);
digitalWrite(ledGREEN, LOW);
digitalWrite(relay1, LOW);
digitalWrite(relay2, LOW);

temperature_read = analogRead(tempPot);
temperature_set = map(temperature_read, 0, 1023, 20, 80); // min temp 20 Degrees C - max temp 80 Degrees
time_read = analogRead(timePot);
time_set = map(time_read, 0, 1023, 5, 40); // min time 5 minutes - max time 40 minutes
void loop(void)
//get temperature
Serial.println("starting 6 second delay");
delay(6000); // 6 seconds
Serial.print("Getting temperature...\n\r");
Serial.print("temperature is: ");
// note that the controls for the relay are reversed. ie: LOW is on and HIGH is off
// this is because it is inverted on the relay board
Serial.print("temp setting: ");
Serial.print("time setting: ");
if (tempC > temperature_set){
Serial.println("**** Temp over set limit ****");
if (hasBeenSet < 1){
Serial.println("starting set delay");
digitalWrite(ledGREEN, HIGH); // green led to show that the timer is about to start
while (delaytimer < time_set){
Serial.print("delay timer: ");Serial.print(delaytimer);Serial.print(" time_set: ");Serial.println(time_set);
delaytimer = ++delaytimer;
delaytimer = 0;
hasBeenSet = ++hasBeenSet; // don't want to start the delay all over again - it's going to take ages for the pipe to cool as it is
Serial.println("Turn relay on"); // under normal operation, the relay is not powered, so turning it on will cut the power to the pump
digitalWrite(relay1, HIGH);
digitalWrite(relay2, HIGH);
digitalWrite(ledRED, HIGH); // red led to show we've cut power to the pump
digitalWrite(ledGREEN, LOW); // can reset the green now
Serial.println("**** Temp under set limit ****");
// back to normal operation
// activate relay now
Serial.println("Turn relay off");
digitalWrite(relay1, LOW);
digitalWrite(relay2, LOW);
digitalWrite(ledRED, LOW);
digitalWrite(ledGREEN, LOW);
// now need to check the temperature again and wait untill it falls below the threshold - so go back to beginning
// the slow cooling of the water in the pipe should give sufficient delay here (in practice when the threshold is set to 40 degrees, the pipe takes 23 minutes to cool)
// start the whole process all over again
hasBeenSet = 0;
void printTemperature(DeviceAddress deviceAddress)
tempC = sensors.getTempC(deviceAddress);
if (tempC == -127.00) {
Serial.print("Error getting temperature");
} else {
Serial.print("C: ");

Step 4: Enjoy

Picture of Enjoy

Sit back and enjoy the peace!
(And hot showers for the rest of the family)


Great idea!

lean04 (author)2014-06-28

nice build!