• Large outdoor whirlpool hot tubs (>2000 liters): Recommended starting dosage of 3–4 chlorine tablets. • Medium-sized home whirlpool hot tubs (1000–1500 liters): Recommended dosage of 1–2 tablets. • Small single-person tubs (<800 liters): 1 tablet is sufficient.

One of the primary purposes of a whirlpool hot tub is to promote relaxation and pain relief. For arthritis patients, pain stems from inflammation, soft tissue tension, and limited mobility. The combination of heat and water flow in a whirlpool hot tub can alleviate pain.

While bathing or showering itself does not directly cause UTIs, if the water is unclean or the method of use is improper, bacteria from the spa hot tub can enter the urinary tract through the urethra or minor skin abrasions, thus increasing the risk of infection.

The real source of the roughness: Calcium carbonate deposits The rough feel of a spa hot tub is usually caused by scale buildup. Scale is mainly composed of calcium carbonate (CaCO₃) or magnesium carbonate (MgCO₃), minerals that come from tap water.

Low-calcium water lacks protection for metals and is prone to slight acidity. Long-term use will corrode nozzles, pipes, and heating elements. Metal corrosion not only shortens equipment lifespan but can also lead to metal dissolution in the water, affecting water quality safety.

The response of bacteria to temperature is not a simple "live or die" situation, but a gradual process. Below 40°C: Bacteria can still exist actively. 37–40°C is precisely the commonly used temperature range for many spa hot tubs, which means that: Normal operating temperatures cannot kill bacteria.