What do you think the bottle of water from Tug Fork represents in this story?

I believe the bottle of Tug Water symbolizes a sort of family tradition. When 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 she complained about how Angel was working on Sunday, and how she should not expect better from a "heathern" Mexican.

Lou Ann sees the coke bottle and tries to remember being baptized in Tug Fork. Angel comes home while Lou Ann nurses Dwayne Ray. He asks whether she has seen his belt buckle or Toros cap. Lou Ann can smell beer on his breath. He asks what is in the coke bottle, and when she tells Angel he pours it down the drain.