The Dragon Gate Eight Directions formula is the practical workhorse of San He water analysis. It produces a single, readable answer to the question: is the water around this property bringing wealth in, or carrying it away? The calculation requires three inputs — the water mouth direction, the property facing direction, and the trigram of the facing — and outputs an auspiciousness rating per direction.
Defining the water mouth
The "water mouth" (水口) is the direction in which water visibly exits the property's vicinity. For urban properties this is often a storm drain, gutter outlet, or the direction in which traffic flows away. For rural properties it is the direction of the nearest stream's flow, or the lowest point of the surrounding land. Multiple water mouths produce a hierarchy: the largest visible flow dominates; smaller ones modify the result. Identifying the water mouth correctly is the single most error-prone step.
Pairing facing direction with the water mouth
The facing direction's trigram (Later Heaven sequence) interacts with the water mouth direction through a fixed lookup table. Each of the 8 trigrams has 4 auspicious water-mouth directions and 4 inauspicious ones. For example, a building with a Kan trigram facing (Water element, north) has auspicious water mouths to the south-east, south-west, east, and west — and inauspicious mouths to the north, north-east, north-west, and south. The pairing logic encodes thousands of years of empirical observation about water and wealth.
Remediating poor configurations
When a property has its water mouth in an inauspicious direction, full structural remediation requires re-routing drainage — usually impractical. Practical remediation: place a heavy rock or earthen feature between the property and the inauspicious water-mouth direction to "block" the energetic exit. Alternatively, install a small water feature (pond, fountain) in the auspicious quadrant to re-route the dominant water-direction reading. Both remediations work because Feng Shui responds to the dominant visible water flow, not just the macro-environment.