Water is basic need in every one’s life. saving and proper usage of water is very important. here is an easy project which will give the alarm when there is rain, so that we can make some actions and save the rain water. as a result, we can increase the water levels of underground water by using underwater recharge technique. rain water detector will detect the rain and make an alert; rain water detector is used in the irrigation field, home automation, communication, auto mobiles, etc. here is the simple and reliable circuit of rain water detector which can be constructed at low cost. in the field of irrigation, it will detect the rain and immediately alert the farmer. in the field of communications, it will boost the power of the antenna and increase the signal strength to send or receive the signals. in the normal house hold application, with the help of rain water detector rain water is saved automatically. this project alert’s the user when it is going to rain. this is helpful for the home maids to protect when they remain inside the home most of the time for work. this can also be used if there is a chemical rain also. this is very commonly used in the industries also. rain alarm circuit produces an audible alarm whenever rain falls. the rain detector circuit is based on two transistors (q1 & q2) and a ne555ic (ic1). the two transistors are wired as a switch which goes on when the base of q1 is shorted to the positive of the supply by the rainwater falling on the sensor. when the transistors are on power supply is available to the ic1 which is wired as an astable multi vibrator. the output of ic1 drives the speaker to produce an alarm. it gives beep sound when water is in contact with the wire.