How can I check whether there phenomenon of

You will need to use the short stick (about 50 cm long). Open the lid and gently insert the stick into the tank until the very end, so that it touches the bottom of the tank. If you feel strong resistance before the stick touches the bottom it means that "clumping" has occured. Push the stick into he tank several times to crush the salt deposits. 

ATTENTION! During crushing do not hit the outer walls and bottom of the tank. This may damage the unit.

If the "clumping" took place in the event of improper use of salt, remove all the salt and rinse the brine tank thoroughly with water. Next add high quality salt to the tank required by the manufacturer.