Are you sure its emitting light?  You can test this easily with a camera. 

Thanks All for your responses!

@Tim, Thanks for your suggestion!.  Its a closed underground tank and I can mount the sensors above the water surface without any difficulty. But there will be lot of moisture inside the tank and I read some where that the moisture inside the tank can damage the sensors.Not sure if its true, that's why I was looking for the water proof sensors, but unfortunately those are not available here. 

Ok.  What is the voltage between PIN3 of LM317T and GND?  Replace the R2 with a wire and check the output voltage at PIN2 and GND, it should be around 1.2V.  If you are not seeing 1.2V, then check the wiring or LM317T.

R2 should be grounded from PIN1 of LM317T, I think you are grounding it from PIN2 of LM317T.

If I keep the ultrasonic sensors (40KHZ/25KHZ) in a sealed plastic container, will they still measure the distance? I want to measure the water level in a tank about 10ft depth and I don’t have the water proof ultrasonic sensors available at my place. Any suggestions are welcome.

Certainly using the micro switch/leaver switch is the simplest way.  In case if you don't want to use mechanical approach, you can do this with IR proximity sensor as well.

If want to test the sensor to rule out if sensor is the issue, you can do it with test circuit in step 4 without multimeter.  All the best!

http://www.instructables.com/id/PIR-Motion-Sensor-Tutorial/step4/Testing-your-PIR/

Refer the linkhttp://www.kerrywong.com/2011/01/22/a-sensitive-diy-ultrasonic-range-sensor/,

Give a try with IN4148 instead of IN4001

Good Luck!  you can refer http://arduino.cc/en/Tutorial/LiquidCrystal for interfacing LCD.

OK try below, The output pins used are pin 4 to 7

You can simply turn them off or on using below code.

Code:

void setup() {               
  // initialize the digital pins as an output.
 
  pinMode(4, OUTPUT); 
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);   
}

void loop() {
  digitalWrite(4, HIGH);   // Turns ON Relay on digital pin 4
  delay(1000);              // wait for a second
  digitalWrite(5, HIGH);    // Turns ON Relay on digital pin 5
  delay(1000);              // wait for a second
  digitalWrite(6, HIGH);   // Turns ON Relay on digital pin 6
  delay(1000);              // wait for a second
  digitalWrite(7, HIGH);    // Turns ON Relay on digital pin 7
  delay(1000);              // wait for a second

  digitalWrite(4, LOW);   // Turns OFF Relay on digital pin 4
  delay(1000);              // wait for a second
  digitalWrite(5, LOW);    // Turns OFF Relay on digital pin 5
  delay(1000);              // wait for a second
  digitalWrite(6, LOW);   // Turns OFF Relay on digital pin 6
  delay(1000);              // wait for a second
  digitalWrite(7, LOW);    // Turns OFF Relay on digital pin 7
  delay(1000);              // wait for a second
}

I am doing my first project and looking for the timer code to turn the output ON / OFF after certain time say 1 minute or 5 minutes.  Currently I am using millis() to achieve this, but I think there will be a better way to do this, any suggestions are welcome!!!

Currently I am using below sketch to turn OFF the output after 1 minute.
********************************

unsigned long time;
void setup() {
  pinMode(13, OUTPUT);
  pinMode(9, INPUT);
}

void loop() {
  if (digitalRead(9) == HIGH)
{
  digitalWrite(13, HIGH);
    time = millis();
   
    }
 
 if (millis() - time > 60000)
{
 digitalWrite(13, LOW);

}
}