What do you think is the symbolic significance of the Tug Fork water? What does Angel's pouring it down the drain symbolize?

Granny Logan has a coke bottle filled with Tug Fork water for baptizing the baby. She reminisces about how Lou Ann was baptized in Tug Fork, then complains about how Angel is working on Sunday and how she should not expect better from a "heathern" Mexican. Angel pouring it down the drain cements Granny's notion of Angel.