Keeping your pool water clean, clear, and bacteria-free is impossible without the right chlorine. But with so many options—Dichlor, Trichlor, Cal Hypo, and Sodium Hypo—how do you know which one to use?
Each type of chlorine has different strengths, uses, and effects on your pool water. Choosing the wrong one can lead to cloudy water, excessive pH swings, or even damage to your pool surfaces.
In this guide, we’ll compare Dichlor vs. Trichlor vs. Cal Hypo vs. Sodium Hypo so you can pick the best chlorine for your pool.
Chlorine Basics: How It Works in Your Pool
Chlorine works by sanitizing the water, killing bacteria, algae, and other contaminants. When chlorine is added to a pool, it forms hypochlorous acid (HOCl), which destroys microorganisms.
The right type of chlorine depends on factors like:
✔ Pool type (inground, above-ground, saltwater)
✔ pH balance & water hardness
✔ How often you maintain your pool
✔ Your budget and convenience
Now, let’s compare the four main types of chlorine.
Dichlor (Sodium Dichloro-S-Triazinetrione)
✅ Best for: Small pools, hot tubs, and quick boosts of chlorine
Dichlor is a stabilized chlorine, meaning it contains cyanuric acid (CYA) to protect chlorine from being destroyed by sunlight. It dissolves fast, making it great for quick water chlorination.
🔹 Available Forms: Granules, Powder
🔹 Chlorine Strength: ~55-62%
🔹 pH Level: Near neutral (6.5)
🔹 Cyanuric Acid (CYA): Yes (adds stabilizer)
Pros of Dichlor:
✔ Dissolves quickly – No residue left behind
✔ Doesn’t raise pH too much – Less impact on water balance
✔ Good for shocking small pools & spas
Cons of Dichlor:
❌ Adds CYA every time you use it – Too much CYA reduces chlorine effectiveness
❌ More expensive than Cal Hypo or Sodium Hypo
💡 Best Use: Great for hot tubs and smaller pools, but for long-term use, be careful with CYA buildup.
Trichlor (Trichloro-S-Triazinetrione)
✅ Best for: Routine maintenance in outdoor pools
Trichlor is a slow-dissolving stabilized chlorine that also contains CYA. It’s often used in chlorine tablets or sticks in floating dispensers or automatic feeders.
🔹 Available Forms: Tablets, Sticks, Granules
🔹 Chlorine Strength: ~90%
🔹 pH Level: Very low (2.8-3.5)
🔹 Cyanuric Acid (CYA): Yes (adds stabilizer)
Pros of Trichlor:
✔ Long-lasting – Ideal for weekly chlorination
✔ Most cost-effective for maintenance
✔ Works well in automatic feeders
Cons of Trichlor:
❌ Highly acidic – Lowers pH, which means you’ll need to add pH increaser (soda ash) regularly
❌ Adds CYA over time – Too much stabilizer reduces chlorine effectiveness
💡 Best Use: Great for routine chlorination, but monitor CYA levels to avoid over-stabilization.
Cal Hypo (Calcium Hypochlorite)
✅ Best for: Pool shocking & high chlorine demand
Calcium Hypochlorite (Cal Hypo) is a powerful unstabilized chlorine that works best for shocking pools. It does not contain CYA, so it won’t add stabilizer to the water.
🔹 Available Forms: Granules, Powder, Tablets
🔹 Chlorine Strength: 65-75%
🔹 pH Level: Very high (10-12)
🔹 Cyanuric Acid (CYA): None
Pros of Cal Hypo:
✔ Powerful shock treatment – Kills algae & bacteria fast
✔ Does not add CYA – Great if stabilizer levels are already high
✔ More affordable than Dichlor & Trichlor
Cons of Cal Hypo:
❌ Raises pH and calcium levels – Can lead to scale buildup
❌ Slow-dissolving – Can leave white residue/cloudy water if not dissolved properly
💡 Best Use: Use for pool shocking, but monitor pH and calcium hardness to prevent scaling.
Sodium Hypo (Sodium Hypochlorite / Liquid Chlorine)
✅ Best for: Commercial pools & those who prefer liquid chlorine
Sodium Hypochlorite (Sodium Hypo) is liquid chlorine, commonly used in large commercial pools. It is unstabilized and contains no CYA.
🔹 Available Forms: Liquid
🔹 Chlorine Strength: 10-12%
🔹 pH Level: High (11-13)
🔹 Cyanuric Acid (CYA): None
Pros of Sodium Hypo:
✔ Fast-acting and easy to use – No dissolving required
✔ Does not add CYA – No risk of stabilizer buildup
✔ Great for large pools
Cons of Sodium Hypo:
❌ Low chlorine concentration – Requires more product to maintain levels
❌ Breaks down quickly – Must be used fresh for maximum strength
❌ Raises pH – Requires acid (muriatic acid) to balance pH
💡 Best Use: Great for large pools and those who prefer liquid chlorine over granules or tablets.
Dichlor vs. Trichlor vs. Cal Hypo vs. Sodium Hypo: Quick Comparison
| Feature | Dichlor | Trichlor | Cal Hypo | Sodium Hypo |
|---|---|---|---|---|
| Chlorine % | 55-62% | 90% | 65-75% | 10-12% |
| Dissolves Fast? | ✅ Yes | ❌ No (slow) | ❌ No (slow) | ✅ Yes (liquid) |
| pH Effect | Neutral | Lowers pH | Raises pH | Raises pH |
| CYA (Stabilizer)? | ✅ Yes | ✅ Yes | ❌ No | ❌ No |
| Best Use | Quick chlorination, hot tubs | Routine maintenance | Shocking, algae control | Large pools, commercial use |
Which Chlorine Type is Best for You?
🏆 Best for Everyday Use: Trichlor Tablets (Long-lasting, low maintenance)
⚡ Best for Pool Shock: Cal Hypo (Powerful, no CYA)
💧 Best for Large Pools: Sodium Hypo (Liquid Chlorine)
🔥 Best for Quick Boosts: Dichlor (Fast-dissolving, good for spas)
💡 Pro Tip: If you use Trichlor or Dichlor, regularly test your CYA levels. If CYA is too high, switch to Cal Hypo or Liquid Chlorine.
Final Thoughts: Choosing the Right Pool Chlorine
Picking the right chlorine is essential for keeping your pool clean, clear, and safe.
- Use Trichlor for routine maintenance
- Use Cal Hypo for shocking
- Use Sodium Hypo for large pools
- Use Dichlor for quick boosts