The main component of vinegar is acetic acid, which is a weak acid. When acetic acid dissolves in water, it releases hydrogen ions, thereby lowering the pH value of the water. Theoretically, adding vinegar to the swim spa tub water could indeed change the pH level.

Studies show that: • Sitting still in 40°C hot water for 30 minutes can burn an additional 25–40 calories; • If the body's thermoregulation response is stronger (e.g., more sweating), it can reach 50–60 calories. In other words: A 30-minute hot tub bath can burn approximately 60–100 calories.

Many people believe that weight loss after a spa hot tub bath is due to "burning fat." In reality, the temporary weight loss is due to the body losing water, not fat. Therefore, while a spa hot tub can slightly accelerate calorie burning, it cannot replace exercise.

If you experience the following symptoms after using a hot tub, you should suspect bacteria in the water: • Skin rash, itching, burning sensation; • Folliculitis or pimple-like red spots; • Localized skin infection or pustules. These are often signs of a hot tub rash caused by bacterial contamination.

For people with heart disease, using a spa hot tub carries potential risks. • Patients with coronary heart disease; • Those with a history of arrhythmia or heart failure; • Those who have had a myocardial infarction; • People with pacemakers (must have their device's safety range confirmed by a doctor).

In unclean spa hot tubs, it often causes a skin condition known as "Hot Tub Folliculitis." This infection manifests as folliculitis, rashes, itching, and even pustules, usually appearing within 24 to 48 hours of exposure.