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How Much Chlorine to Add to Your Pool
Quick answer: To raise free chlorine by 1 ppm, add roughly 80 mL of liquid chlorine (12.5% strength) or 15 g of granular calcium hypochlorite (65% strength) per 10,000 litres of pool water. Most home pools need to sit between 1–3 ppm free chlorine day to day, or up to 5 ppm if you're running a higher stabiliser (CYA) level.
That's the number people usually come here for. The rest of this guide covers how to work it out for your own pool size, why the "right" target isn't always 1–3 ppm, and the mistakes that quietly waste chlorine.
Work Out the Dose for Your Pool
The maths is the same regardless of pool size — you're just scaling a base rate.
Per 10,000 litres, to raise free chlorine by 1 ppm:
| Product | Strength | Dose |
|---|---|---|
| Liquid chlorine (sodium hypochlorite) | 12.5% available chlorine | ~80 mL |
| Granular chlorine (calcium hypochlorite) | 65% available chlorine | ~15 g |
| Stabilised granules (dichlor) | 56% available chlorine | ~18 g |
For a 50,000-litre pool — a common Australian in-ground size — that's roughly 400 mL of liquid chlorine or 75 g of granular chlorine to move free chlorine up by 1 ppm. If your test shows you're sitting at 0.5 ppm and you want to get to 2 ppm, you're dosing for a 1.5 ppm lift, so multiply accordingly.
Concentration varies by brand and batch, so treat these as planning numbers, not a substitute for testing after you dose.
What Target Should You Actually Aim For?
Most Australian health guidelines for private pools sit in the 1–3 ppm free chlorine range, with 1 ppm as a practical minimum and 3 ppm as a comfortable ceiling for everyday use. Two things push that number around:
Stabiliser (cyanuric acid) level. CYA protects chlorine from UV breakdown, but higher CYA also reduces how effective a given chlorine reading actually is. Once CYA climbs above roughly 50 ppm, the effective sanitising power of a 2 ppm reading drops noticeably — which is why pools with high stabiliser are often run at the top of the range, or higher, to compensate. If you can't remember the last time you tested CYA, that's usually the first thing to check before you assume a dosing chart is wrong.
Bather load and heat. Chlorine burns off faster in hot weather, under UV, and after a pool party. A spike in swimmers or a run of 35°C days will drop your reading faster than the "normal" rate, so test more often through summer rather than sticking to a fixed weekly top-up.
Free Chlorine vs Total Chlorine — Why the Gap Matters
Free chlorine is the active sanitiser available to kill bacteria and algae. Total chlorine includes free chlorine plus combined chlorine — chlorine that's already reacted with contaminants (sweat, sunscreen, urine) and is no longer doing useful work.
Subtract free from total and you get combined chlorine, sometimes called chloramines. If that gap is above about 0.5 ppm, that's usually the source of the "chlorine smell" people associate with too much chlorine — it's actually a sign you need more, in the form of a shock dose, not less.
Shock Dosing
Shock dosing means temporarily pushing free chlorine well above normal range — typically to 10 ppm or more — to burn off combined chlorine and knock down algae or bacteria that a maintenance dose won't touch. Use it after heavy bather loads, visible algae, cloudy water that won't clear, or if combined chlorine keeps creeping up despite normal dosing.
To shock a 50,000-litre pool to roughly 10 ppm from a baseline of 2 ppm, you're dosing for an 8 ppm lift — around 3.2 L of liquid chlorine or 600 g of granular chlorine, using the per-10,000-litre rates above. Run the filter continuously until the reading drops back into normal range before swimming again.
Common Dosing Mistakes
Adding chlorine to concentrated chemicals, not water. Always add product to water, never water to product — for both safety and how evenly it disperses. Granular chlorine should be pre-dissolved in a bucket of water before it goes into the pool, especially with a vinyl liner or fibreglass surface, to avoid bleaching or pitting.
Dosing off a total chlorine reading instead of free chlorine. If your test kit only gives you total chlorine, you're flying blind on combined chlorine and may be over- or under-dosing without knowing it. A kit that separates free and combined readings — a reagent-based test or a photometer rather than basic strips — makes the difference obvious.
Guessing pool volume. Dosing math is only as good as your litres figure. Length × width × average depth × 1,000 (in metres) gives a reasonable estimate for a rectangular pool; irregular shapes need a rough average across the deep and shallow ends.
Never mixing chlorine types together. Don't combine liquid chlorine, granular chlorine, and stabilised (dichlor/trichlor) products in the same dose or the same storage space — some combinations are a genuine safety hazard, not just a wasted dose.
Salt Chlorinator Pools
If your pool runs a salt chlorinator rather than manual dosing, the same free chlorine and CYA targets still apply — the chlorinator is just generating chlorine from salt in the water instead of you adding it by hand. The dosing rates above are for manual top-ups or pools without a working chlorinator; if your salt system is struggling to hold a reading, check the cell output and salt level before manually dosing on top of it.
Mineral and Low-Chemical Pool Systems
Some pools use mineral-based or low-chemical systems that significantly reduce or replace traditional chlorine sanitisation using a combination of mineral salts, UV, ozone, or other technologies.
If your pool runs one of these systems, the dosing rates in this guide may not apply directly. Key differences to be aware of:
- Many mineral systems still use a small residual chlorine level (often 0.5–1 ppm) as a backup sanitiser — check your system's specific target range, as it's typically lower than a standard pool.
- Stabiliser (CYA) is generally not used in these systems, so the CYA adjustment notes above don't apply.
- Standard DPD test kits can still measure residual chlorine in mineral pools, but won't measure ozone or other sanitiser levels.
- Always follow your system supplier's dosing guidelines rather than standard chlorine charts — over-dosing chlorine into a mineral system can disrupt the balance the system is designed to maintain.
For a full breakdown of how these systems differ, see our guide: Mineral Pools vs Low-Chlorine Pools: What's the Difference?
Frequently Asked Questions
How much chlorine per litre for a pool?
Roughly 1 mg (1 ppm) of available chlorine per litre is the working target for most home pools. To raise free chlorine by 1 ppm, add approximately 0.008 mL of liquid chlorine (12.5%) or 0.0015 g of granular chlorine (65%) per litre of pool water. For a 50,000-litre pool, that's ~400 mL of liquid chlorine or ~75 g of granular chlorine per 1 ppm rise.
Can you add too much chlorine to a pool?
Yes — chlorine above about 5 ppm can bleach vinyl liners, irritate skin and eyes, and isn't necessary for normal maintenance. If a test comes back high, let it dissipate naturally (sunlight breaks down free chlorine) before swimming rather than trying to dilute it further.
How often should I add chlorine to my pool?
Test two to three times a week in summer and weekly in cooler months, dosing whenever the reading drops below 1 ppm rather than on a fixed schedule. Hot weather, heavy rain, and high bather loads all accelerate chlorine loss, so test more frequently during those periods.
Why does my pool smell like chlorine if the reading is low?
That smell is combined chlorine (chloramines), not an excess of free chlorine. It means chlorine has already reacted with contaminants and is no longer active. The fix is a shock dose to burn off the chloramines — not less chlorine.
How much chlorine do I need to shock a pool?
Shock dosing typically means raising free chlorine to 10 ppm or more. For a 50,000-litre pool starting at 2 ppm, you need to dose for an 8 ppm lift — approximately 3.2 litres of liquid chlorine (12.5%) or 600 g of granular chlorine (65%). Run the filter continuously until the level drops back to 1–3 ppm before swimming.