GFCI receptacles are required by code within roughly 6 feet of a water source (shampoo bowl, manicure soak, pedicure basin) in salons. The PRIMARY reason is:

Explanation

Water and the wet human body are both conductors. If an energized appliance falls into a shampoo bowl or pedicure tub, or if a person touches an energized component while standing in water, a current path opens through the person to ground. A GFCI continuously compares the current on the hot wire to the current returning on the neutral wire; an imbalance of just a few milliamps (4 to 6 mA) signals leakage to ground (a person) and trips the receptacle in milliseconds, well before the current is sufficient to stop a heart. This is why the National Electrical Code and California salon practice require GFCI protection within roughly 6 feet of water sources, consistent with CCR Title 16 §979.2 safe-equipment-use duties.