Hot tubs have the same chemical needs as a pool, except the amount of chemicals used is lower. Although hot tubs are smaller, the water will still get dirty and need some treatments to sanitize and clarify the water so you can use the hot tub without any health risks.
Sanitizer is used on hot tubs in lesser amounts than what is used in a swimming pool. Bromine tablets are placed in a floating dispenser that floats in the water of the hot tub at all times similar to the swimming pool, which uses a floating chlorinator floating in the water. In place of bromine for sanitizing the hot tub, you can use granular chlorine instead, which is another chemical used for swimming pools. Ideal chlorine readings are one to three parts per million.
Hot tub pH is adjusted using pH increaser or pH reducer. Soda ash is used in swimming pools and hot tubs to raise the pH of the water. Muriatic acid is used to lower the pH in hot tubs and swimming pools. The ideal reading for pH in hot tubs is 7.4 to 7.6 parts per million. Soda ash is also used to raise the total alkalinity of the water and muriatic acid is used to lower the total alkalinity. The ideal reading of total alkalinity in a hot tub or pool is 80 to 100 parts per million.
Hot tub clarifier is not used in swimming pools, but is used in hot tubs to get rid of body oils, scum and reduce scum lines in the hot tub. Although there are many different brands of clarifiers, you should add one that will control scale and stains. Generally, a product with an enzyme base will work the best as a clarifier.
You may need to treat the calcium hardness in the hot tub water. The ideal reading for calcium hardness in a hot tub is 200 to 400 parts per million. Calcium hardness is lowered using calcium chloride for swimming pools and hot tubs. If the calcium hardness is too high, you can simply drain half of the water from the hot tub and add new water.