How to Apply Chlorine Shock to Your Hot Tub

A woman sitting in a hot tub with the blowers on.
  • 1 hours
  • Beginner
  • 15-25
What You'll Need
Chlorine bleach
Large sponge
Water filter (optional)
pH test strips
pH chemical
Water clarifier
Stain control solution
Alkalinity test kit
Alkalinity chemical
Hot tub chlorine shock
Non-chlorine shock
Scale remover
Cartridge cleaner solution

High temperatures can be a breeding ground for bacteria in water, so sanitizing your hot tub regularly is an important part of your regular home maintenance. Chlorine is actually one of the two chemicals that can be used to decontaminate your spa, bromine is the other one.

Bromine tends to be the more expensive option of the two, but chlorine requires more upkeep because it becomes ineffective for sanitizing much more quickly at hot temperatures. Never mix these chemicals; instead, choose one method and stick to it unless you drain and thoroughly clean your tub before switching. For advice on how to properly use a chlorine shock treatment, follow the steps below.

Warning: Chlorine shock is also used for pools, so be sure that the treatment you buy is specified for hot tub use.

Step 1 - Empty the Spa Water and Clean Out the Hot Tub

Drain the hot tub water and clean the tub shell with a diluted solution made from half a cup of household chlorine bleach and three gallons of warm water. Wipe down the shell with this cleanser and a large sponge. Rinse it thoroughly with cold water after cleaning, and dry it off with big absorbent towels. Now is the perfect time to also clean or change the filter as needed. Rinse the scum filter bags outside the hot tub and replace them in their holder.

Step 2 - Fill the Hot Tub Again

Refill the spa with clean, fresh water, up to the halfway level of the upper skimmer. Prime the pumps and filter unit by bleeding off some air. Then, turn on the water heater to warm the water to 80 degrees Fahrenheit (27 degrees Celsius), and run the filter for three hours of the next 12, using a timer.

Step 3 - Add Hot Tub Chemicals to Adjust the pH and Alkalinity

Test the water's pH and then adjust it up or down with a suitable pH chemical until it reaches a tested level between 7.6 and 8.2. Add water clarifier and stain control products according to the manufacturer’s directions. Test the alkalinity of the water next and modify it as needed to a tested level of between 100 and 150 parts per million (ppm) by adding the appropriate product to raise or lower the alkaline level.

Step 4 - Disinfect the Hot Tub with the Chlorine

These hot tub chemicals are formulated to work together to keep hot tub water safe and sanitized. Add a spa-specific chlorine every two days or more to meet testing requirements. After the chlorine has dissolved, add two ounces of Activate Spa Shock, the non-chlorine formula. Test the water to ensure the chlorine content is at three ppm.

Step 5 - Maintain the Hot Tub Water Weekly

Perform the tests for pH, alkalinity, and chlorine content every week. Continue to add granular chlorine weekly, and rinse out the filter and scum filter bags.

Step 6 - Monthly Maintenance

You will need to clean around the skimmers once a month with a scale remover. Lower the water level in the hot tub by six inches, and wipe around the skimmers to clean off the built-up scale from hard water.

Also, clean the filter thoroughly every month with a cartridge cleaner solution recommended by your pool dealer, or more often if many bathers use the hot tub. Replace the filter when it can no longer keep the water clear and sparkling.

These procedures, done regularly and according to the directions provided with the hot tub chemicals, will keep your hot tub sanitized, bubbly, and relaxing for you and all the other bathers who enjoy it with you.