A pail closet or pail privy or dirt closet was a room used for the disposal of human excreta, under the "pail system" (or Rochdale system) of waste removal. The "closet" (a word which had long meant "toilet" in one usage) was a small outhouse (privy) which contained a seat, underneath which a portable receptacle was placed. This bucket (pail), into which the user would defecate, was removed and emptied by the local authority on a regular basis. The contents, known euphemistically as night soil, would either be incinerated or composted into fertiliser.
Although the more advanced water closet (flush toilet) was popular in wealthy homes, the lack of an adequate water supply and poor sewerage meant that in 19th-century England, in working-class neighbourhoods, towns and cities often chose dry conservancy methods of waste disposal. The pail closet was an evolution of the midden closet (privy midden), an impractical and unsanitary amenity considered a nuisance to public health. The pail system was popular in France and England, particularly in the historic Lancashire town of Rochdale, from which the system commonly took its name. The pail closet was not without its own problems; if the pail was not emptied on a regular basis, it overflowed and became unhygienic. Some manufacturers lined the pail with absorbent materials, and other designs used mixtures of dry earth or ash to disguise the smell.
Improved water supplies and sewerage systems in England led directly to the replacement of the pail closet during the early 20th century. Municipal collection of pail toilets (dunnies) continued in Australia into the second half of the twentieth century. In the western world, the pail closet has now been almost completely replaced by the flush toilet. However, similar systems still exist in less developed countries, and are discussed at sanitation.