Head (watercraft)

In modern boats, the heads look similar to seated flush toilets but use a system of valves and pumps that brings seawater or fresh water into the toilet and discharges waste into a holding tank or out through the hull.^[1][2] In small boats the pump is often hand operated. The cleaning mechanism is easily blocked if too much toilet paper or other fibrous material is put down the pan.^[1] Electrically-pumped toilets are also available and more water-efficient, which can enable using fresh water to reduce odors and corrosion.^[2][3]

Discharge of sewage from boats is regulated by international agreements and national laws to reduce marine pollution, including the International Convention for the Prevention of Pollution from Ships and the United States Clean Water Act (see regulation of ship pollution in the United States). Marine sanitation devices treat, process, and store raw sewage.^[4] Modern boats commonly have a holding tank so that sewage can be stored and later discharged at a sanitary pumpout facility on shore or discharged into the sea at a legal distance from shore.^[1][4]

By the late 17th century, sailing ships were typically built with latrines, called "seats of ease" or "seats of easement", in the form of openings in the bow fitted with discharge pipes that led to the sea.^[5] The captain and officers had more private toilets at the stern of the ship in the quarter galleries, although the mechanism was the same.^[5] During the era when all hands aboard a vessel were men, the heads received most of their use for defecation; for routine urination, a pissdale was easier to access and simpler to use.^[6][7] Officers also used chamber pots.^[7][8]

18th century naval ships had similar facilities, although by the 1790s some ships may have had a few flush toilets.^[8] The journal of Aaron Thomas aboard HMS Lapwing in the Caribbean Sea in the 1790s records that a canvas tube was attached, presumably by the ship's sailmaker, to a superstructure beside the bowsprit near the figurehead, ending just above the normal waterline.^{[citation needed]}