Quick Answer

For most pools, choose stabilized chlorine tablets (trichlor, also sold as TCCA 90) for daily sanitising, and keep a fast-dissolving shock chlorine (dichlor granules or calcium hypochlorite) for periodic shocking and emergencies. Use liquid chlorine (sodium hypochlorite) if your pool already has high stabilizer (cyanuric acid) or you want a no-residue option. Pick by pool type, sun exposure, and how much time you want to spend on maintenance.

Table of Contents

1. The 5 main types of pool chlorine

2. Pool chlorine types compared (table)

3. Which chlorine is best for your situation?

4. Stabilized vs unstabilized chlorine

5. Tablets vs granules vs liquid

6. Mistakes to avoid when choosing

7. How to dose your chosen chlorine correctly

8. FAQ

9. Conclusion

The 5 Main Types of Pool Chlorine

Almost every chlorine product sold for swimming pools falls into one of five chemical types. They all sanitise water by releasing free chlorine, but they differ in strength, pH, stabilizer content, and how fast they dissolve. Understanding those differences is what tells you which one belongs in your pool.

1. Trichlor (TCCA 90 Chlorine Tablets)

Trichloroisocyanuric acid, sold as TCCA 90 tablets, contains about 90% available chlorine and includes a built-in stabilizer (cyanuric acid) that protects chlorine from sunlight. It dissolves slowly, which makes it the standard choice for floaters, skimmer baskets, and automatic chlorine feeders. It is acidic (pH roughly 2.7–3.3 in solution), so pool pH needs watching. See our TCCA 90 Chlorine Tablets 20 kg.

2. Dichlor (Sodium Dichloroisocyanurate Granules)

Dichlor contains roughly 55–62% available chlorine, dissolves quickly, and is close to pH-neutral, so it barely moves your pH. It also contains stabilizer. It suits fast top-ups, shocking, and starting up a new or freshly filled pool.

3. Calcium Hypochlorite (Cal Hypo)

Cal hypo contains about 65–75% available chlorine, has no stabilizer, and is strongly alkaline. It is a popular shock treatment because it dissolves fast and oxidises hard, but it adds calcium to the water, so it can raise calcium hardness and cause scaling over time.

4. Liquid Chlorine (Sodium Hypochlorite)

Liquid chlorine is a bleach-style solution, usually 10–12.5% strength in pool grade. It has no stabilizer and leaves only salt behind, so it is excellent for pools that already have enough stabilizer. It loses strength in storage and in heat, and it is alkaline, so it raises pH.

5. Chlorine Gas and Salt-Generated Chlorine

Chlorine gas is used only in large commercial and municipal systems with trained operators. Salt chlorine generators make chlorine on-site from dissolved salt. Both are valid but are equipment decisions rather than a product you buy off the shelf for routine dosing.

Pool Chlorine Types Compared

Which Chlorine Is Best for Your Situation?

Outdoor residential pool in strong sun

Choose trichlor tablets as your daily chlorine. The built-in stabilizer slows sunlight loss, so free chlorine holds longer between doses. Add a fast shock product when needed.

Commercial pool, hotel, resort or apartment complex

Choose bulk TCCA 90 tablets with an automatic pool chlorinator. Fewer top-ups, predictable dosing, and lower labour cost. Bulk 20 kg packs also reduce cost per dose. For scale-related questions, contact our team.

Small or above-ground pool, or a spa

Choose dichlor granules or small tablets used in a floater. Because these are small water volumes, avoid full-strength trichlor tablets in the skimmer, which can overdose the water.

Indoor pool

Indoor pools get little sunlight, so stabilizer is not needed for sun protection. Liquid chlorine or cal hypo are often better because they add no extra cyanuric acid.

Pool with high stabilizer (cyanuric acid above about 50–60 ppm)

Switch to liquid chlorine or cal hypo until stabilizer comes down. Continued use of trichlor or dichlor keeps adding cyanuric acid, which can weaken chlorine's effectiveness. This effect is often called chlorine lock.

Green, cloudy or freshly contaminated pool

Use a shock treatment (cal hypo, dichlor, or liquid chlorine), then return to your daily chlorine. See our guide on treating green, black and mustard algae.

Stabilized vs Unstabilized Chlorine

Stabilized chlorine (trichlor and dichlor) contains cyanuric acid, which acts like sunscreen for chlorine. Unstabilized chlorine (cal hypo and liquid chlorine) has none, so sunlight can destroy a large share of it within hours on an outdoor pool.

A useful rule: outdoors, keep cyanuric acid roughly in the 30–50 ppm range so chlorine is protected without being suppressed. Test it, don't guess. Our guide on how to test your pool's chlorine level shows how to read chlorine, and a full test kit will also measure stabilizer.

Tablets vs Granules vs Liquid

• Tablets: slow, steady, low effort. Best for routine dosing. Never crush them or dump them straight onto the pool floor.

• Granules and powder: faster and more flexible. Good for top-ups and shocking. Dissolve according to the label before adding, to avoid surface damage.

• Liquid: instant, clean, and stabilizer-free, but bulky, short shelf life, and needs careful handling.

For a deeper format comparison, read Tablets, Granules & Powder: A Buyer's Guide.

Mistakes to Avoid When Choosing Pool Chlorine

1. Using only trichlor for months. Stabilizer keeps building up. Test and rotate to liquid or cal hypo if it climbs.

2. Ignoring pH. Trichlor lowers pH and cal hypo raises it. Balance both with pH plus and pH minus.

3. Mixing chlorine types or chemicals. Never mix different chlorine products or add acid to chlorine. Add chemicals separately and store them apart.

4. Choosing by price per kilogram alone. A cheaper, lower-strength product can cost more per unit of usable chlorine. Compare available chlorine percentage.

5. Skipping testing. The right chlorine type still fails if you don't measure. Follow our routine in Pool Water Balancing.

How to Dose Your Chosen Chlorine Correctly

Whichever type you choose, aim for 1–3 ppm free chlorine in a typical pool and test 2–3 times a week. Start low, re-test after circulation, and adjust in small steps. Always follow the manufacturer's label, keep products in original sealed containers in a cool, dry, ventilated place, and never store different chlorine types together.

Check your local health regulations and pool-operator guidance for commercial pools, since required ranges can differ.

FAQs

Which chlorine is best for a swimming pool?

For most outdoor pools, stabilized trichlor (TCCA 90) tablets are the best everyday chlorine, paired with a fast shock chlorine for periodic treatment.

What is the difference between trichlor and dichlor?

Trichlor is about 90% chlorine, dissolves slowly, and lowers pH. Dichlor is about 55–62% chlorine, dissolves quickly, and is close to pH-neutral. Both contain stabilizer.

Is liquid chlorine better than tablets?

Neither is universally better. Liquid chlorine adds no stabilizer and acts instantly, so it suits indoor pools and pools with high stabilizer. Tablets are easier for steady daily dosing outdoors.

Can I use bleach instead of pool chlorine?

Plain household bleach is much weaker and varies in strength, so it is not a reliable substitute. Pool-grade liquid chlorine is a more consistent option.

Can I mix different types of chlorine?

Do not mix chlorine products together or with acids. Add each product separately, and store them apart, because mixing can release dangerous gas.

What is the best chlorine for a commercial pool?

Bulk TCCA 90 tablets used through an automatic chlorinator are a common choice for commercial pools because of steady release and lower labour.

How do I know if my pool has too much stabilizer?

Test cyanuric acid. If it is above roughly 50–60 ppm and chlorine seems weak, switch to unstabilized chlorine and dilute with fresh water.

Conclusion

The best chlorine for your pool isn't one product, it's the one that matches your pool. Use trichlor TCCA 90 tablets for steady outdoor sanitising, dichlor or cal hypo granules for shocking and top-ups, and liquid chlorine when you need stabilizer-free chlorine. Test regularly, keep pH and alkalinity balanced, and rotate chlorine types if stabilizer builds up.

Ready to order? Browse TCCA 90 Chlorine Tablets 20 kg, 10 kg tablets, or chlorine granules, or see the full Pool Chemicals range. For bulk or commercial supply, contact Pearl Water.