Simple water level indicator

This circuit is the simplest I have seen in the entire web. Here we use transistor as a switch; and gets ON when water reaches each level. In simple words, think of an automatic switch, that turn on lights when water level raises and reaches each point. The transistor is used to drive 5 LEDs or more if required.

Please note, the circuit is not my design. Its taken from simple-water-level-idicator. I just constructed it, and this is not a step by step instructions am giving here. But a guidance for whom want do and use this in real. So its not just the circuit, you need to buy couple of things. Average cost is Rs 600. Dont get surprised, if you want a neat, well fixed product this is the cost. See the pictures below.

Approx. Cost Distribution:
Common board - Rs 45
Step down transformer (6V 500MA)- Rs 50
Components in board (5 transistors,few resistors, capacitors,LEDs etc) - Rs 50
Buzzer - Rs 20
LAN/Ethernet cable (20 mtrs) straight crimped with two  board sockets - Rs 300
Two plastic boxes (One at inside room, one fitted near to tank as a junction box for the LAN cable and sensor wires to tank*) - Rs 45
Other (wires/board sockets/switch/fuse and holder/screw packet/box holder etc.) - Rs 100

Added capacitor between base and ground of each transistor, to avoid LED blinking even when sensor is not passing current to transistor. See below, LAN cable is connected from sensor wires at tank*. This is the best way, rather than running 5-6 wires from top terrace to your room. Your design would be kind of neat and plug and play stuff :) Switch for AC mains also attached on right side.

 Buzzer and fuse to mains AC attached on left side. See in the pic, that four LEDs are on, means tank is half. The last LED will glow when tank is 3/4th and buzzer will sound when its full. The only drawback i found is that, buzzer sound is not loud enough even after filtering of AC current.

So thats it. If you have any questions or doubts please post in comments. I will be happy to help.

Update: 
The issue of low buzzer sound can be solved by designing the particular transistor circuit as common emitter, while the other LED driver circuits are common collector. That means connect the buzzer at collector and ground the emitter, this will give a voltage gain at collector on saturation point.

Note: * - Sensor wires are just aluminium wires, but not put in tank, as my water tank doesnt have any holes or opening(when lid closed; its fully closed) to draw the wires out. So i just put the long sensor wires in the air escape pipe that you see as an extension to over flow pipe. I think its the best place to keep sensor wires, So that you dont need to put holes in your water tank. :)