Water level Detection using Ultrasonic Sensor and arduino I'm making a water level detector to control my motor which supplies water in water tank and for that I'm going to use ultrasonic sensor to be attached to tank lid. My question is whether the vapor arising from water inside the tank hamper the overall working of ultrasonic sensor and/or it may be damaged permanently. I can cover complete ultrasonic sensor using hot glue stick but cannot cover its diaphragm as it will block sound waves. Please suggest something.
A friend of mine worked on a liquid level monitoring project, and after many iterations finally abandoned the kinds of sensors you're talking about. Ultimately he just pointed a cheap USB webcam at the thing and used OpenCV and the edge detection algorithm to find the level of the water.  Then it's just a matter of doing some math using the dimensions of the container, to figure out how full it is.  

If you are using a clear container and if you have the option of using a Raspberry Pi (or a PC, whatever) that can run OpenCV, you might find that option worth exploring.