I think the apostle John likes to use historical detail and physical realities to illustrate, emphasise and point to divine realities and spiritual truth. For example, he notes that the jars used to turn water into wine were for Jewish rites of purification (John 2:6), I think alluding to the true purification that will come through Jesus' blood, when his hour has come. Or when the healing of the blind man leads to discussion of spiritual blindness (John 9). Or the simple statement, "And it was night" (John 13:30), as Judas departs to betray the Christ. We might also think of the raising of Lazarus from the dead (John 11) or other instances.
When we were reading through John 4 on Thursday night, I was struck by how the Samaritan woman, after hearing Jesus speak of "living water" (4:10) he can give, which, if someone drinks of it, that person "will never be thirsty again", and it "will become in him a spring of water welling up to eternal life" (4:14), after hearing these words, she "left her water jar" (4:28) and told others about the Christ, directing them to him, so that they too could hear and meet "the Saviour of the world" (4:42). While John doesn't explicitly tell us that the woman received eternal life, or that she drank of those living waters, I think the note that she "left her water jar", which was to carry the kind of water of which if we drink, we "will be thirsty again", is meant to show us that she has indeed drunk of the living waters that only Christ can give, that she herself now has that spring in her, so that through her, others also may hear the words of Christ and drink as well.
Have we left our water jars, or do we still need to listen to the One who can satisfy our real thirsts?