⚡ Quick Reference
- Purpose: Oxidize contaminants and restore chlorine effectiveness
- Target Level: 10+ ppm free chlorine (10x combined chlorine minimum)
- Frequency: Weekly or as needed for problems
- Best Time: Evening/night to prevent UV degradation
Shocking (also called super-chlorination or oxidation) is the process of adding a large dose of sanitizer to your pool to eliminate contaminants, break down chloramines, and restore crystal-clear water. It's one of the most important regular maintenance tasks for any pool.
🛁 Spa/Hot Tub Note
Spa shocking requires completely different protocols than pool shocking. For detailed spa-specific guidance including dosages, frequency, and product recommendations, see our comprehensive Spa Shock Guide.
Why Shock | When to Shock | Shock Types | How to Shock | Dosage Guide | Troubleshooting | Pro Tips
Why Your Pool Needs Shocking
Even with regular chlorination, your pool accumulates contaminants that regular sanitizer levels can't handle:
- Combined chlorines (chloramines): Created when chlorine binds with swimmer waste, causing that "chlorine smell" and eye irritation
- Organic waste: Leaves, pollen, body oils, sunscreen, and other debris
- Algae spores: Microscopic algae that haven't bloomed yet but are present
- Bacteria and viruses: Pathogens that require higher chlorine levels to eliminate
🚫 Myth Buster
"That chlorine smell means too much chlorine"
Actually, the opposite is true! A strong chlorine odor indicates chloramines (combined chlorine) - a sign you need to shock. Properly balanced pools with adequate free chlorine have little to no smell.
When to Shock Your Pool
Regular Maintenance Schedule
- Weekly: Most pools benefit from weekly shocking as preventive maintenance
- After heavy use: Pool parties, lots of swimmers, or extended use periods
- After rain: Storms introduce contaminants and can dilute sanitizer levels
Problem Indicators
Shock immediately when you notice:
| Problem | What It Means | Shock Response |
|---|---|---|
| Strong chlorine smell | High chloramines | Double shock dose |
| Cloudy water | Organic contamination | Standard shock + filtration |
| Algae growth | Sanitizer overwhelmed | Triple shock dose |
| Eye/skin irritation | Chloramine buildup | Heavy shock treatment |
Types of Pool Shock
Calcium Hypochlorite (Cal Hypo)
Pros: Most powerful, cost-effective, long shelf life, adds available chlorine
Cons: Raises pH and calcium hardness, requires pre-dissolving
Best for: Regular maintenance, severe contamination, outdoor pools
Sodium Dichlor
Pros: pH neutral, dissolves easily, won't cloud water, contains stabilizer
Cons: More expensive, adds CYA over time, lower available chlorine
Best for: Saltwater pools, routine shocking, indoor pools
Potassium Monopersulfate (Non-Chlorine Shock)
Pros: No chlorine added, won't affect pH/hardness, can swim immediately
Cons: Doesn't kill algae/bacteria, more expensive, requires existing chlorine
Best for: Spas, routine oxidation, breaking down organic waste
Browse our complete selection of pool shock treatments including calcium hypochlorite, dichlor, and non-chlorine options for every pool type and situation.
How to Shock Your Pool Properly
📋 Step-by-Step Shocking Process
- Test water chemistry - Check FC, CC, pH, and TA first
- Balance pH if needed - Ideal range 7.2-7.6 for maximum shock effectiveness
- Calculate shock dose - See dosage guide below
- Pre-dissolve granular shock - Use plastic bucket, never metal
- Add shock in evening - UV rays destroy chlorine during daylight
- Pour around pool perimeter - Never dump in one spot
- Run pump continuously - 8-24 hours for full circulation
- Test and repeat if needed - Target 10+ ppm free chlorine
⚠️ Safety First
- Never mix different shock products
- Always add shock to water, never water to shock
- Use plastic containers and utensils only
- Store shock products in cool, dry place away from other chemicals
- Don't swim until chlorine drops below 3 ppm
Shock Dosage Guide
Standard Maintenance Shocking
| Pool Size | Cal Hypo (65%) | Dichlor (56%) |
|---|---|---|
| 10,000 gal | 1.5 lbs | 1.75 lbs |
| 20,000 gal | 3 lbs | 3.5 lbs |
| 30,000 gal | 4.5 lbs | 5.25 lbs |
Problem Treatment Dosing
- Chloramines (breakpoint chlorination): 10x the combined chlorine reading
- Algae treatment: 2-3x normal shock dose depending on severity
- After contamination events: Double normal dose
Common Shocking Problems
"I shocked but the water is still cloudy/green"
- Insufficient dose: Use 2-3x more shock for severe problems
- Poor circulation: Run pump 24/7 until clear
- Filter issues: Clean/backwash filter, may need DE or new cartridges
- pH too high: Shock is less effective above 7.6
"The chlorine reading won't stay up"
- Chlorine demand: Pool needs multiple shock treatments
- Stabilizer too low: UV destroying chlorine too quickly
- Major contamination: May need to drain and refill
"Shock made my water cloudy"
- Calcium precipitation: High calcium + cal hypo shock
- Dead algae: Filter out debris, may take 24-48 hours
- Over-shocking: Too much too fast can cloud water temporarily
Pro Shocking Tips
🎯 Expert Shocking Strategies
- Timing is everything: Shock at dusk/night when UV is minimal
- Pre-dissolve properly: Hot water dissolves shock faster and more completely
- Test combined chlorine: If CC > 0.2 ppm, you need breakpoint chlorination
- Don't over-stabilize: Frequent dichlor shocking raises CYA quickly
- Brush first: Loosen debris before shocking for better results
- Double-shock algae: Green pools need aggressive treatment
- Monitor pH afterward: Cal hypo will raise pH significantly
- Keep records: Track shock frequency and effectiveness
🌡️ Seasonal Shocking
Summer: Shock more frequently due to heat, UV, and heavy use. Consider shocking twice weekly during peak season.
Winter: Reduce frequency but don't skip entirely. Monthly shocking prevents problems during pool closing/opening.
Spring Opening: Triple shock dose to eliminate winter buildup and algae spores.