The fundamental reason for black substances flowing from the spa jacuzzi tub nozzles is that: The internal circulation system of the spa jacuzzi tub is constantly in a humid, warm environment rich in organic residues, a natural breeding ground for biofilm, mold, and impurities.

Immersing your head in a spa jacuzzi bathtub poses several risks, including microbial infection, chemical irritation, physical injury, and suffocation. Even if the spa jacuzzi bathtub is sterilized, direct head contact with water can still cause health problems.

Soap residue is rich in organic matter, providing an ideal environment for microbial growth. Especially when the spa jacuzzi bathtub is not thoroughly cleaned for a long time, these substances will form a "biofilm" in the pipes, causing odor and bacterial accumulation problems.

Too low a temperature will weaken the relaxing and soothing effects; too high a temperature may cause an increased heart rate, dehydration, or dizziness. 36°C to 40°C is the ideal temperature range for most people using a spa jacuzzi.

Under normal circumstances, spa jacuzzi bathtub water should be clear, soft, odorless, and have a natural feel. If a "slippery" feeling occurs, it usually means that the chemical balance in the water has been disrupted or organic matter has accumulated.

In high-end spa jacuzzi bathtubs, the two are often used in combination to create a dual hydrotherapy experience: first, bubbles soothe the nerves, then water flow deeply relaxes the muscles, achieving balanced relaxation throughout the body.