A: A sacrarium is “special sink used for the reverent disposal of sacred substances. This sink has a cover, a basin, and a special pipe and drain that empty directly into the earth, rather than into the sewer system” (USCCB, Built of Living Stones, 236).
Precious or sacred items are disposed of, when possible, by returning them to the ground. Sacred books or vessels, for example, are often buried on church grounds or in a Catholic cemetery. Other items, such as altar linens, are first burned and then the ashes are buried. Liquids, rather than pouring them into sewer or septic systems, find their way to the earth by direct pouring or through the sacrarium. The water used to rinse purificators, corporals, or vessels can be poured into the sacrarium. Baptismal water, and even old holy oils, can similarly be poured into the sacrarium. If cloths are used to clean a spill of the Precious Blood, these are rinsed above the sacrarium. The Precious Blood is never poured into the sacrarium, but must be consumed (see Built of Living Stones, 236-7).
J.B. O’Connell summarizes the history and legislation on the sacrarium (also called a piscina, literally, “fish pool”) in his helpful 1955 book, Church Building and Furnishing (University of Notre Dame Press). He writes:
“The sacrarium is mentioned from about the 9th century for the disposal of the water which the celebrant of Mass has used to cleanse the chalice and his hands (Leo IV, about 850, directed that a sacrarium should be built near the altar). It was Innocent III (1216) who first ordered that two piscinae be used, one for the wine and water with which the chalice was cleansed, the other for the water the celebrant used to wash his hands. Later he ruled that the priest should drink the ablutions, but only gradually did this practice obtain, and it was not widespread until the 14th century…. In some of the medieval churches, [the sacrarium] was quite an architectural feature—encased with elaborate moldings, sometimes surmounted by a canopy.”
As for the brief legislation in 1955, O’Connell says that the sacrarium leads into a lead, copper, or earthenware pipe “which will conduct liquids or small solids directly into the earth (not into a drain used for other purposes), where a hole is made, filled with broken fragments of stone or brick, so that the water may soak into the ground. The sacrarium itself (the basin) should have a lockable cover, and be labelled “Sacrarium” or “Piscina” to prevent it being used for profane purposes” (88-89).