Is it stated somewhere in writing exactly where the Chalice and other cups should be purified after communion. . At the altar, credance table, or in the sacristy etc…
EWTN provides an answer to your question.
I find the GIRM confusing regarding the correct place. I some places it seems to direct that the credence table be used. But in other places it seems to say that the altar is an option, at least when a priest does the purifications.
From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from romanrite.com/girm.html :
“279. The sacred vessels are purified by the priest, the deacon, or an instituted acolyte after Communion or after Mass, insofar as possible at the credence table.” (This is under the heading “IV. SOME GENERAL NORMS FOR ALL FORMS OF MASS”).
“270. The priest purifies the chalice at the credence table or at the altar. If the chalice is purified at the altar, it may be carried to the credence table by the minister or may again be placed on the altar at the side.” (Under the heading “III. MASS AT WHICH ONLY ONE MINISTER PARTICIPATES”)
“163. … Upon returning to the altar, the priest collects any fragments that may remain. Then, standing at the altar or at the credence table, he purifies the paten or ciborium over the chalice then purifies the chalice, …” (Under the heading “A. MASS WITHOUT A DEACON”.)
“249. … The deacon, however, consumes at the altar all that remains of the Precious Blood, assisted, if necessary, by some of the concelebrants. He carries the chalice to the credence table and there he or a duly instituted acolyte purifies, wipes and arranges it in the usual way.” (Under the heading “II. CONCELEBRATED MASS”).
“192. … When no deacon is present, a duly instituted acolyte carries the sacred vessels to the credence table and there purifies, wipes, and arranges them in the usual way.” (Under the heading “C. THE DUTIES OF THE ACOLYTE”).
“183. When the distribution of Communion is completed, the deacon returns to the altar with the priest and collects the fragments, if any remain, and then carries the chalice and other sacred vessels to the credence table, where he purifies them and arranges them in the usual way while the priest returns to the chair.” (Under the heading “B. MASS WITH A DEACON”)