Hi Vengai.
From references on the site here to "LCD display" and keyboard reading in the tutorials and forum you can get the hardest parts of the software design done. The rest is pretty easy. Can you get access to a C compiler or are you using assembler ?

Any of the small 8051s will do what you need. I suggest the Philips or Temic devices will be ideal.

You will need some temperature sensor to read water temperature too. A thermistor would be ideal, easy to read and correct and easy to fasten to pipes and things.

Steve