The sacrarium [pronounced \ sə-ˈkrer-ē-əm \] is a special sink found in the sacristy of most Catholic churches. The drain bypasses municipal sewer systems and runs straight down into the earth.
The basin often hides beneath a hinged cover. The sacrarium, or piscina, provides for the proper disposal of sacred substances.
For example, after Mass the vessels which held the Body and Blood of Christ are rinsed and cleansed there. In this way any remaining particles of Communion are washed into the earth.
The sacrarium has also been used for the disposal of other substances: old baptismal water, leftover ashes, and last year’s holy oils.
There was a time in history when the leftover consecrated wine was poured down the sacrarium, but today the Blood of Christ is consumed by the faithful, not discarded.
If the consecrated wine is ever spilled during the Mass, it is to be cleaned up with care. Accidents happen, and the instructions for Mass offer this procedure: The area should be washed, and the water poured down the sacrarium.
Likewise, if the consecrated host is spoiled or soiled that makes consumption impossible, the sacred body can be dissolved in water then poured down the sacrarium.
The presence of the sacrarium shows our reverent care for holy things. When materials designated for a sacred purpose have completed their service, we honor them even in their disposal. By returning our sacred substances to the earth beneath the church building, we honor them, the ground over which we worship, and the God who created them and consecrated them to nourish our faith. (9:36)