How to Shock a Hot Tub (and How Often)

Shocking a hot tub means adding a larger dose of oxidizer to burn off the body oils, lotions, sweat and other gunk that build up between soaks. Your everyday sanitizer keeps the water safe, but it can't keep up with that buildup on its own. A weekly shock keeps the water clear, cuts down on odor and helps your sanitizer work.

How often should you shock?

For most home hot tubs, once a week is the rule of thumb. Shock again after a party or heavy use, after a refill, or any time the water looks dull or smells strongly of chlorine.

Chlorine shock or non-chlorine shock?

  • Non-chlorine shock (potassium monopersulfate, often called MPS), such as Leisure Time Renew, oxidizes the gunk without raising chlorine levels much, so you can usually get back in sooner. It works with chlorine or bromine tubs, and in bromine tubs it helps turn used bromide back into active bromine.
  • Chlorine shock, such as a larger dose of Spa 56 chlorine granules, oxidizes and sanitizes at the same time. It's a good choice when the water is cloudy, smells off or after heavy use. You'll need to wait longer before soaking.

Many owners use non-chlorine shock for the weekly routine and a chlorine shock now and then when the water needs a reset. Browse all hot tub shock and oxidizers.

How to shock a hot tub, step by step

  1. Test first. Dip a test strip and adjust total alkalinity and pH if they're off. Shock works best when pH is in range (about 7.2 to 7.8).
  2. Uncover the tub and turn on the jets. Leave the cover off while you shock so gases can escape.
  3. Measure the dose from the label, based on your tub's water volume.
  4. Add the shock to the water with the jets running, following the label (some products are pre-dissolved in a bucket of water first).
  5. Let it circulate with the cover off for at least 20 minutes, or as long as the label says.
  6. Re-test before soaking. Wait until sanitizer is back in its normal range.

Common mistakes

  • Closing the cover right away. Trapped gases can damage the cover and pillows.
  • Shocking with pH way off. High pH makes chlorine much less effective, so you burn chemicals for little result. See how to balance pH and alkalinity.
  • Skipping the filter. If the water stays cloudy after shocking, the filter may be clogged. Rinse it and use a filter cleaner regularly. See how to clean a hot tub filter.

Related reading

Safety first: always follow the directions on the product label and your hot tub maker's manual. Add chemicals to the water one at a time, never mix chemicals together, and store them dry, cool and out of reach of kids and pets. Questions? Send us a message.

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