On March 28, 1945 the submarine departed from Kiel for its first training patrol in the North Sea, returning on March 30. The submarine departed from Horten for a one-day patrol on April 2, and its first active patrol began on April 6, when it departed from Kristiansand. On April 14, while on patrol, the vessel sank after the toilet was operated improperly.
U-1206 was one of the late war boats fitted with new deepwater high-pressure toilets which allowed them to be used while running at depth. Flushing these facilities was extremely complicated and special technicians were trained to operate them.
On April 14, 1945, 8 miles (13 km) off Peterhead, Scotland, while cruising at a depth of 200 feet (61 m), misuse of the new toilet caused large amounts of water to flood the boat. According to the Commander’s official report, while in the engine room helping to repair one of the diesel engines, he was informed that a malfunction involving the toilet caused a leak in the forward section. The leak flooded the submarine’s batteries (located beneath the toilet) causing them to release chlorine gas, leaving him with no alternative but to surface. Once surfaced, U-1206 was discovered and bombed by British patrols, forcing Schlitt to scuttle the submarine. One man died in the attack, three men drowned in the heavy seas after abandoning the vessel and 46 were captured. Source