I've got (at least) one more provocative thought from Pryor. He maintains that when Jesus "gave up his spirit" (Jn 19:30), he was releasing the Holy Spirit. In other words, the Holy Spirit became available to the New Covenant community at the point of Christ's death.
...there can be no doubt that John sees a real link between the death of Jesus and the gift of the Spirit as v. 34 demonstrates. We have already noted the association between 7:37-39 and 19:34. For John, the crucifixion scene is a 'visible picture presentation' of Jesus' exaltation and glorification. It is in fact part of that stage of Jesus' work where he functions as glorified Lord. When we remember that water has frequently been the symbol of the revelation and the Spirit which result in eternal life and which are the gifts of Jesus...then we can make sense of the blood and water which flow from the side of Jesus. The blood symbolises the reality of his death, and the water the Spirit which flows out to the believing community. The gift of the Spirit is indeed the fulfillment of the promises of the Scriptures, the inauguration of the age and that 'giving over' (v.30) of the Spirit, that outpouring of the Spirit (v. 34), comes from the crucified/exalted Jesus.
John Pryor, John: Evangelist of the Covenant People, 82.
Perhaps John spent a good deal of time meditating on Ezekiel 47:1-12, where water flows from the temple, bringing fresh creation and healing. Jesus is the true temple (Jn 2:21), and his destruction/restoration causes the water of the Spirit to flow in the hearts of people (Jn 7:37-39).