Hot tubs are great additions to the home, but the tubs do need regular maintenance so the water stays clear and clean. Shock is one chemical that is added to the water to keep bacteria from forming. You will need to use nonchlorine and chlorine shock in the water, as well as other chemicals to keep the hot tub's pH in the proper range.
When to Shock
Maintain the chlorine level in the hot tub by adding shock to the tub once a week during the warmer months, or every two weeks during winter if the hot tub doesn't get used as much as it does in the summer. Shock is added to the water during the evening so it has at least 12 hours to work in the water. Sunlight causes shock to dissipate quickly.
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After filling the hot tub with fresh water, or if the tub has heavy usage, you will want to use a chlorine shock. Shock is a sanitizer that kills living organisms, bacteria and other water contaminants. The downside to using chlorine is that you must wait at least eight hours before using the hot tub. If the chlorine application is for regular maintenance, you can use nonchlorine shock.
Nonchlorine shock, which contains potassium peroxymonosulfate, doesn't have the chlorine smell to it the way chlorine shock does, and the hot tub can be used sooner than if you had used chlorine shock. After adding the nonchlorine shock to the tub, you can safely use the spa after 15 minutes. Nonchlorine shock is normally used for regular maintenance of the water after the first initial dose of shock when you fill the hot tub with fresh water.
After shocking a pool with a chlorine-based shock, you need to test and adjust the other chemical levels, which can change after an application of chlorine, but not with a nonchlorine shock. Test the pH levels, which must be between 7.2 and 7.6, and the total alkalinity, which must be between 80 and 120 parts per million (ppm). The calcium hardness of the water must be between 150 and 400 ppm.