The reredorter was a communal toilet found in mediaeval monasteries in Western Europe and later also in some New World monasteries. It was normally attached to the south end or the east side of the monks' dormitory on the east of the main cloister with seats arranged on the first floor of the building allowing direct access from the dormitory with waste was usually carried away by a stream, river or conduit. Sophisticated water engineering was used at Cîteaux Abbey, Roche Abbey and the Carmelite Desierto de Los Leones in Mexico to both that these rooms remained fresh and that the effluent did not pollute water needed for cooking and washing. The word is composed from dorter and the Middle English prefix rere-, coming from Anglo-French rere: backward, behind, from Latin retro.
In some monasteries there were two reredorters, one for the monks and one for the lay brothers. The lay brothers’ reredorter was most often to the west of the cloister, attached to their dormitory in a similar way to that of the monks.
