Head

The head (or heads) is a ship's water closet or toilet.

The term derives from sailing ships in which the toilet area for the regular sailors was placed at the head or bow of the ship. In sailing ships this position was sensible for two reasons. First, since most vessels of the era could not sail directly into the wind, ^[1] the winds came mostly across the rear of the ship ^[2] placing the head essentially downwind. Secondly, if placed somewhat above the water line, vents or slots cut near the floor level would allow normal wave action to wash out the facility. Only the captain had his private toilet near his quarters, below the poop deck.^{[citation needed]}

In many modern boats, the heads look similar to a seated, land-type toilet, but have several technical differences. Rather than using a cistern and gravity to flush the waste away through a plumbing trap to a drain, there is a system of valves and pumps that brings sea water into the toilet and pumps the waste out through the hull. In small boats the pump is often hand operated. The cleaning mechanism is often easily blocked if too much toilet paper or other fibrous material is put down the pan.

Submarines

The head on the submarine HMS Alliance (P417)

Submarine heads face the problem that at greater depths higher water pressure makes it harder to pump the waste out through the hull. As a result early systems could be complicated with the head fitted to the US S class being described as almost taking an engineer to operate.^[3] Making a mistake resulted in the waste being expelled back into the body of the submarine.^[3] The toilet on the World War 1 British E class was considered so poor by the captain of HMS E35 that he preferred the crew to wait to relieve themselves until the submarine surfaced at night.^[4] As a result many submarines used the heads as an extra storage space for provisions.^[4]

Notes