Non-potable water in our area is used for watering the lawns, it is provided through the city's pressurized irrigation system and one does not need to use house (potable) water for watering the lawn. Generally, in our area, there is a seasonal fee, mine is $75 for the season, March through October. It is not good for filling up swimming pools, above ground or inground. Older subdivisions in our area do not have it available, mostly new ones built out in the last 10 years.
So, the subdivision may have water run-off system that captures the water and then the water can be pumped back to house(s) for watering. Probably similar to a pressurized irrigation system.
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jbt