In Deponia, only the rich and powerful have clear water.
Like mayors! Get into the Mayor's office.
Finally! Any signs of clear water? Or any water?
There is a water symbol in the desk. Your father used to have this office. Some other thing else also belonged to your father.
The divining rod! Wenzel left it to his basement. This must work as a key.
Use the divining rod to the water symbol in the Mayor's office and behold, a secret compartment!
There are more secrets if you just find them. Use your globe.. I mean head!
There is a secret compartment in the globe, too. How neat. And you get a glass!
Yes, use the key you got from the first secret compartment to the keyhole in the second secret compartment to open the third secret compartment (huh!).
Have a drink! You deserve it. Don't be a barbarian, use a glass.
Pour the booze into the glass.