Simple water leak alarm

Our life is unpredictable and the least expected can always happen. For example, a water leak may occur in a place that seemed particularly safe. In order to react in time and find out about such a leak of water from the initial drops, I will offer you the option of a simple alarm that each of you can make with your own hands.
The alarm does not contain scarce parts, consumes virtually no energy in standby mode, and one battery will last for more than 3 years. The minimal dimensions allow the device to be installed in any place where control is required.
This simple and uncomplicated device will help you and give a signal in case of a leak. And your timely awareness will allow you to quickly take the necessary measures (turn off the tap, call a plumber, etc.). This will save your property and, possibly, the property of your neighbors.

Since we are talking about neighbors, from my experience I can say that there are small leaks that do not manifest themselves in any way (since they are in protective boxes hiding the pipes) and at one fine moment a neighbor appears on the doorstep with complaints...
This alarm will save you from this and give you a signal about a drip leak instantly.
So, we need:

• 3V CR1632 coin cell battery.
  One transistor BC517, BC816 or any other NPN structure. Domestic analogue - kt315, kt3102.
  
• Resistor 1-2 mega ohms.
  
• Buzzer, you can buy here - aliexpress.
  

The transistor acts as a sensitive switch. And the resistor prevents the transistor from opening from various false interference and high humidity. The alarm sensor consists of two outputs; when water enters, a circuit is closed to which an alarm is triggered, indicating a water leak.
The scheme is simple. We solder according to the diagram.

I decided to collect everything in a plastic bun lid. I sawed off the neck and put everything on hot glue. I checked the alarm first.


The device does not require setup or adjustment and starts working immediately after power is applied.

For longer operation, you can use “AA” or “AAA” batteries (“finger” and “pinky” batteries). Then the alarm will last for 5 years.
If the volume of the buzzer does not seem very loud to you, replace the battery with a Krona battery with a voltage of 9 volts.
It is better to make several such mini alarms and place them in possible leakage areas: under the washing machine, in the bathroom, behind the grille under the heating radiator, etc.
I wish you never have this happen:

Device assembly video:

Thanks to all!