Q. 1. How does one dispose of the Precious Blood that is not consumed during the Holy Mass? Should it be poured down the sink or the sacrarium?
A. 1. Any remaining Precious Blood must be consumed by the priest or the attending Extraordinary Eucharistic Ministers.
52. When more of the Precious Blood remains than was necessary for Communion, and if not consumed by the bishop or priest celebrant, "the deacon immediately and reverently consumes at the altar all of the Blood of Christ which remains; he may be assisted, if needs dictate, by other deacons and priests." (54) When there are extraordinary ministers of Holy Communion, they may consume what remains of the Precious Blood from their chalice of distribution with permission of the diocesan bishop.
54. The Precious Blood may not be reserved, except for giving Communion to someone who is sick. Only sick people who are unable to receive Communion under the form of bread may receive it under the form of wine alone at the discretion of the priest. If not consecrated at a Mass in the presence of the sick person, the Blood of the Lord is kept in a properly covered vessel and is placed in the tabernacle after Communion. The Precious Blood should be carried to the sick in a vessel that is closed in such a way as to eliminate all danger of spilling. If some of the Precious Blood remains after the sick person has received Communion, it should be consumed by the minister, who should also see to it that the vessel is properly purified.
55. The reverence due to the Precious Blood of the Lord demands that it be fully consumed after Communion is completed and never be poured into the ground or the sacrarium.
[Source: Norms for the Distribution and Reception of Holy Communion Under Both Kinds in the Dioceses of the United States of America; Approved by the United States Conference of Catholic Bishops on June 14, 2001; Congregation for Divine Worship and the Discipline of the Sacraments.]