Diaconicon

The diaconicon contains the thalassidion (piscina), a sink that drains into an honorable place where liquids such as the water used to wash holy things may be poured, and where the clergy may wash their hands before serving the Divine Liturgy.

The diaconicon will usually have cabinets or drawers where the vestments and church hangings (antependia) may be safely stored.

Here will also be kept the reserved charcoal, and a place for heating the zeon (boiling water that is poured into the chalice before Holy Communion).

Because the diaconicon is located behind the iconostasis it is considered to be a holy place, and only those who have a specific liturgical duty to perform should go in, and any regulations pertaining to entry into the sanctuary may apply here as well.

[citation needed] During the reign of Justin II (565–574), owing to a change in the liturgy, the diaconicon and prothesis came to be located in separate apses at the east end of the sanctuary.