You would need to get Wenzel into Mayor's office.

Wenzel's house is in the bottom

Yeah, Wenzel would like to bring water to the Mayor. He thinks he might have a water vein in his basement.

But there seems to be water reservoir on top of Wenzel's apartment.

You could pour down water into Wenzel's chimney.

Yes, the pipe does not stop on top of the chimney. And there is a lid. Maybe you could devise an impromptu lid-opener and pipe-stoppener.

Pull the chimney lid open with something and at the same time stop the pipe on top of it. Easy.

For lifting you could use something floating. There was a feast at the Town hall some time ago.

Get the balloons from the Assembly Hall behind the wooden door. Use the doorknob.

An empty balloon does not lift anything.

Balloons are filled with gas.

There is laughing gas in Doctor Gizmo's office. Pull the lever most up and fill the balloon with laughing gas.

It is. If you let go of the balloon, it will fly away and most definitely won't stop the pipe and open the lid.

Some kind of hook would attach the balloon to the lid so it won't fly away.

Combine the hook and the balloon. The impromptu devise to keep the lid open and stop the pipe is ready!

Now, use the balloon to open the lid of the chimney. You would have to do it beneath.

Wenzel does all his cookings in his bathroom. There is a furnace. Put the balloon (and the hook) into the furnace. It will raise the lid and the balloon is there to stop the pipe.

Go kick the pipe and pull the lever to get the (dirty) water flowing into the chimney.

Yes, the water is not staying in the basement where it should.

Usually the blumping does not work at Deponia. Maybe you could "fix" the pipe in the basement.

Like drilling a hole into the pipe. Go get a drill.

Go and pull the lever again. Heh heh, poor Wenzel...

Argh! But at least he took his place in the queue, finally!