Cal Hypo, also known as calcium hypochlorite, and pool shock, also known as chlorinating shock, are two popular chemicals used to sanitize swimming pools. While they are both chlorine-based chemicals, there are some key differences between Cal Hypo and shock that pool owners should understand.
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What is Cal Hypo?
Cal Hypo, or calcium hypochlorite, is a chlorine-based chemical that is commonly used as a sanitizer in swimming pools. It comes in both granular and tablet forms. The active ingredient in Cal Hypo is calcium hypochlorite, which provides a concentrated source of chlorine to kill bacteria and algae in pool water.
Some key facts about Cal Hypo:
- Provides 65% available chlorine
- Raises pH as it dissolves
- Lasts up to one week in pool water
- Must be manually added and dissolved in the pool
- Granular form dissolves quickly, tablets dissolve slowly over time
Cal Hypo is a popular pool sanitizer because it provides a steady source of chlorine to continually sanitize pool water. It lasts longer than liquid chlorine before needing to be replenished. Cal Hypo raises the pH as it dissolves, so pH down chemicals are often needed to maintain proper water balance.
What is Pool Shock?
Pool shock, or chlorinating shock, provides a high dose of chlorine to sanitize swimming pools. It is used to “shock” the pool when chlorine levels get low or when adding large amounts of water. The main active ingredient in pool shock is either calcium hypochlorite or sodium hypochlorite.
Some key facts about pool shock:
- Provides 60-75% available chlorine
- Works quickly dissolving in water
- Lasts 1-2 days before chlorine dissipates
- Used for shocking/superchlorination
- Comes in granular and liquid forms
Pool shock is essentially a concentrated, fast-dissolving form of chlorine designed to raise the chlorine levels quickly when given a “shock” treatment. Liquid pool shock works the fastest since it does not need to dissolve first. Pool shock lasts just 1-2 days before chlorine levels drop again.
Differences Between Cal Hypo and Shock
While Cal Hypo and shock (or chlorinating shock) are both chlorine-based chemicals for pools, there are some important differences between the two:
| Difference | Cal Hypo | Shock |
|---|---|---|
| Form | Granular or tablet | Granular or liquid |
| Chlorine Content | 65% | 60-75% |
| Purpose | Ongoing sanitizer | Shock/raise chlorine quickly |
| Lasts | Up to 1 week | 1-2 days |
| pH Impact | Raises pH | Low pH |
| Form | Weekly maintenance | As needed shocking |
As you can see, Cal Hypo provides a steady, longer-lasting source of chlorine for regular pool sanitizing. Shock is used for quick chlorine boosts when shocking the pool. While both contain chlorine, Cal Hypo and shock have different uses and effects on pool water chemistry.
Can You Use Cal Hypo and Shock Together?
Since Cal Hypo and shock perform different sanitizing roles, they can absolutely be used together in a pool care regimen. Here is how Cal Hypo and shock work together:
- Use Cal Hypo weekly to provide a steady chlorine residual.
- Use shock as needed when chlorine gets low or when adding large amounts of water.
- Test water regularly and shock if chlorine drops below 3 ppm.
- Supplement with liquid chlorine if needed to maintain proper levels.
Maintaining an appropriate chlorine residual prevents algae growth and kills bacteria. Having both Cal Hypo and shock on hand allows you to maintain chlorine through weekly Cal Hypo additions and shock when levels drop low. Using both provides a comprehensive sanitizer plan.
Tips for Using Cal Hypo and Shock Together
Here are some tips for successfully using Cal Hypo and shock together in your pool care routine:
- Test water 1-2 times per week and adjust chemicals accordingly.
- Shock the pool if chlorine drops below 3 ppm.
- Switch between granular and liquid shock for flexibility.
- Broadcast Cal Hypo across the pool for even dissolve time.
- Run the filter and allow time for Cal Hypo to fully dissolve.
- Balance pH after shocking to avoid very low or high pH.
Using both Cal Hypo and shock may take some trial and error to get the routine right for your specific pool. Be sure to test water frequently, add Cal Hypo regularly, and shock whenever chlorine drops too low. With some practice, you’ll get the hang of using both chemicals together!
Frequently Asked Questions
Is it okay to add Cal Hypo and shock on the same day?
Yes, you can add Cal Hypo and shock on the same day if needed. Just make sure to balance your pH after adding both. Test water again in a day or two as well to ensure chlorine is within the ideal range. Add each chemical in different parts of the pool.
Which raises pH more, Cal Hypo or shock?
Cal Hypo will raise pH more than shock. Cal Hypo is calcium hypochlorite, which increases pH as it dissolves in water. Shock made from sodium hypochlorite has a more neutral pH. Test and balance pH after using either chemical.
Is liquid or granular shock better?
Liquid shock works the fastest since it does not have to dissolve first. But granular shock is more budget-friendly. Use granular shock for weekly shocking and liquid for fast chlorine boosts as needed. Having both on hand is useful.
How often should you shock a pool?
How often you should shock depends on several factors like pool size, bather load, and weather. Typically shocking 1-2 times per week is recommended, especially with heavy use. It’s best to test water regularly and shock whenever chlorine drops below 3 ppm.
Conclusion
While Cal Hypo and shock are both chlorine-based pool chemicals, they serve different sanitizing purposes. Understanding the unique benefits of each allows you to use them together for comprehensive pool care. Cal Hypo offers steady, long-lasting chlorine through weekly or biweekly additions. Shock provides occasional boosts of chlorine when levels drop low. Using both chemicals together forms an effective 1-2 punch against algae, bacteria, and swimmer contaminants in pool water.