Calcium hypochlorite is a commonly used chlorine-containing disinfectant in swimming pool maintenance , providing both disinfection and shock treatment capabilities. The following are its specific uses, advantages, disadvantages, and precautions:
The role of calcium hypochlorite
-
Powerful disinfection : Releases free chlorine
after dissolving to kill bacteria, viruses and algae. -
Shock treatment :
When used in high concentrations, it can quickly oxidize organic matter (such as sweat and urine) and decompose chloramines (eliminating chlorine odor). -
Supplement calcium hardness :
After dissolution, it will slightly increase the calcium ions in the water (but the effect is limited and it cannot replace calcium chloride ).
When is calcium hypochlorite necessary?
-
Regular disinfection :
As an alternative to daily chlorine disinfection (compared to liquid sodium hypochlorite or chlorine tablets). -
Chlorine shock treatment :
Rapidly increases free chlorine levels when water is turbid, algae is growing, or there are too many chloramines. -
Outdoor swimming pools or high temperature environments :
Calcium hypochlorite has better stability and is suitable for outdoor swimming pools (it is more resistant to UV degradation than liquid chlorine).
Comparison with other chlorine agents
| characteristic | calcium hypochlorite | Sodium hypochlorite (liquid chlorine) | Trichloroisocyanuric acid (chlorine tablets) |
|---|---|---|---|
| Available chlorine content | 65-75% | 10-12% | 90% |
| Dissolution rate | Medium speed (pre-dissolved) | fast | Slow (sustained release) |
| pH Effect | Significantly increases pH (requires additional acid adjustment) | Slightly increase pH | Slightly lower pH |
| Effect of calcium hardness | Slight increase | No impact | No impact |
| Applicable Scenarios | Shock treatment/daily disinfection | Daily disinfection | Long-term sustained-release disinfection |
Usage
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Daily disinfection : Calculate the dosage
based on a target free chlorine value of 1-3 ppm (for example, add approximately 16-48 grams of calcium hypochlorite to 10 tons of water). -
Shock treatment : Calculated
based on 10-30 ppm free chlorine (160-480 grams for 10 tons of water), it is recommended to apply it in the evening to avoid ultraviolet rays. -
Dissolution steps :
- Pre-dissolve in warm water in a plastic bucket (avoid metal containers).
- Sprinkle evenly into the deep water area of the swimming pool and turn on the circulation pump for 6-8 hours.
- Check free chlorine levels and wait until they are <5 ppm before swimming.
Notes
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pH adjustment :
Calcium hypochlorite will significantly increase the pH (approximately 0.8 for every 10 ppm of chlorine). It is necessary to adjust the pH to 7.2-7.6 in advance with hydrochloric acid or a pH reducer . -
Calcium hardness monitoring :
Long-term use may lead to excessive calcium hardness (>400 ppm), causing scale, and requires regular testing. -
Safe operation :
- The powder easily absorbs moisture and clumps, so it needs to be sealed and stored in a cool place.
- When dissolving, it releases heat and chlorine gas. Wear gloves and a mask and keep ventilation.
-
Compatibility :
Do not mix directly with acids or other oxidants (such as potassium persulfate), as this may cause explosion.
Alternatives
- If you are concerned about calcium hardness being too high: use sodium hypochlorite (liquid chlorine) or trichloroisocyanuric acid (chlorine tablets) instead .
- If a non-chlorine shock is required: choose potassium persulfate (MPS) .
Summary and Recommendations
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Recommended usage scenarios :
Calcium hypochlorite is suitable for swimming pools that require strong disinfection + shock treatment and have low calcium hardness (such as in soft water areas). -
Use with caution :
Use with caution when the water quality already has high calcium hardness (>300 ppm) or the pH is prone to being high.