The Association of Pool and Spa Professionals recommends free chlorine levels for both swimming pools and hot tubs be kept between 2.0 and 4.0 ppm. However, the Center for Disease Control recommends free chlorine stay above 1 ppm in pools and 3 ppm in hot tubs.
Content specifically related to hot tubs
Cyanuric acid stabilizes free chlorine by preventing it from evaporating from UV sunlight, which increases the lifespan of free chlorine but decreases its ability to sanitize swimming pool water.
The ideal pH level in both swimming pools and hot tubs is 7.4 to 7.6. This is the level where water is most comfortable for swimmers while also maximizing chlorine’s sanitizing ability.
Swimming Pool alkalinity (often called total alkalinity) is a measurement of the concentration of alkaline materials in your pool. Alkaline materials stabilize pH but buffer chlorine sanitation.
To keep your swimming pool or hot tub at its best, it’s important that you accurately calculate your water volume. All of the chemical balancing recommendations you receive from the Pool Calculator are based on it. The Pool Volume Calculator that is built into the Pool Calculator is designed to help you calculate the volume of rectangular, oval, and circular pools quickly. You can get the volume in metric units (liters) or in imperial units (gallons).