HTH Cal Hypo Pool Shock 13.3 oz Pack of 6 — Fast-Acting Chlorine Boost, No CYA, Works for Vinyl & Saltwater

HTH Multi-Use Shock Treatment (Cal Hypo) is a fast-acting, fast-dissolving chlorine boost that sanitizes, clarifies, and helps prevent algae and bacteria without adding stabilizer (CYA).

Keep pool water clear and balanced with this 13.3 oz pack of six single-dose Cal Hypo shock treatments from HTH. Designed to act quickly, the formula raises free chlorine levels to address common water issues within 24 hours, dissolves rapidly for easy application, and works in all pool types including vinyl-lined and saltwater systems. Use alongside routine testing to maintain safe, swim-ready water and reduce cloudy or green pools.

How quickly will this shock clear cloudy or algae-prone water?

HTH Cal Hypo shock is formulated to react quickly and begin sanitizing immediately on contact. Most typical pool water problems show marked improvement within a day, though severity and environmental factors affect timeline.

• Fast-acting Cal Hypo active ingredient for quick chlorine boost
• Designed to resolve roughly 90% of common pool issues in 24 hours
• Better results when pool chemistry is pre-tested and balanced

Is this shock safe for my vinyl-lined or saltwater pool?

Yes—this HTH formula is compatible with vinyl-lined pools and saltwater systems. It sanitizes without adding cyanuric acid, helping avoid overstabilization that can reduce sanitizer effectiveness over time.

• Works with vinyl liners and saltwater chlorinators
• No added CYA (stabilizer), reducing risk of chlorine lock
• Use per label instructions to protect surfaces and equipment

How do I apply the 13.3 oz doses and how often should I shock?

Apply each pre-measured 13.3 oz pack according to the label, typically by dissolving in a bucket or broadcasting carefully around the deep end with the pump running. Weekly shock treatments are recommended as part of routine maintenance, or immediately after heavy use, storms, or algae flare-ups.

• Follow package directions for safe dilution and broadcast application
• Run filter during and after application to distribute sanitizer
• Combine with HTH 6-Way Test Strips to check levels twice weekly

Will using this shock affect my pool chemistry long-term?

A single application raises free chlorine to sanitize; it does not add cyanuric acid, so it won’t cause stabilizer buildup. Regular testing and balancing are still required to maintain ideal pH, alkalinity, and chlorine levels.

• Cal Hypo provides chlorine without adding stabilizer (CYA)
• Short-term chlorine increase dissipates with filtration and sunlight exposure
• Routine testing prevents recurring imbalances and optimizes performance

Who is this for: Pool owners and service professionals seeking a reliable, quick-dissolving chlorine shock for routine maintenance and problem-solving. HTH 13.3 oz Cal Hypo shock is ideal if you want pre-measured doses for easy application, compatibility with vinyl and saltwater pools, and a sanitizer that avoids adding stabilizer. For best results, pair with test strips and follow label safety directions when handling and applying.