Mysterious Blockage

WC Pipe Found to Suck Air, Slowing Down the Ship’s Propeller

A Special MWM Moment of Prof. Dr.-Ing. Hubert Hitzinger

Here’s the story: In the course of the engine replacement of a large inland ship, the living quarters, too, were modernized. Among other things, the freeboard toilet was replaced with a flush toilet. However, this measure resulted in a strange effect: Despite the higher performance of the new MWM main engine, the ship was unable to reach the intended speed.

Following several delays and complaints, the shipowner, who also happened to live on the ship, threatened to terminate the contract and demand a refund. The MWM engineers were permitted to take a last test tour on the Rhine from Mannheim to Karlsruhe. Meanwhile, the shipowner’s wife had also boarded the ship.


As previously, the ship leisurely chugged along. Suddenly, a loud scream sounded from the cabin. At the same time, the ship made a forward leap, plowing through the river at great speed. The scream came from where the new toilet was located. The shipowner’s wife was found sitting on the toilet, unable to get up. The lady was discretely rescued, and immediately, the ship slowed down again.

A careful scrutiny revealed the issue: During the conversion at the shipyard, the outlet of the new toilet had been placed right next to the stern tube in front of the ship’s propeller. The propeller was constantly sucking air through the WC outlet, causing a substantial vacuum. At the same time, the air inflow was impairing the propeller performance. Like a plug, the stately lady had blocked the flow of air. Thus, the propeller performance returned to normal, resulting in a speed increase. However, the vacuum had also sucked the lady onto the WC, which is why she screamed.

The MWM engineers quickly solved the problem by means of some simple steps, and the shipowner and his wife were happy.


MWM History. Future Needs Tradition.

More about the history of the company, the MWM brand and the experience in developing and optimizing stationary gas engines.

Read more


Brand expert Christian Steguweit on the development of the MWM brand

Read more

The brand quiz Take part and win parts 1 to 10

Read more

The MWM Kit for distributors for the brand anniversary

Read more

Photo credit

Photograph: Rhine and Imperial Cathedral in Speyer (© Nailia Schwarz, Adobe Stock)