Concrete will also degrade the plastic bottle causing failure. Flowing water from a broken water distribution main mixes with fire caused by a broken gas line. Any water that you make up yourself needs to be treated. If left untreated over time, it becomes contaminated with bacteria and algae. Another source of water is the hot water heater.
Every water heater has a drain valve near the bottom.
Use extreme caution. Let the water cool. Some sediment at the bottom of the tank may at first make water flowing out look murky. Continue to drain water until it becomes clear. Melted Ice Cubes are a source of water.