Saltwater chlorine generators: how they actually work, and how to size one
An SWG is just an electrolytic chlorine factory bolted into your plumbing. Choosing the right size, and knowing how to run it, is what makes the difference between 5 years of trouble-free operation and 5 cell replacements.
Last updated: 2 June 2026
A saltwater chlorine generator (SWG) is, mechanically, a simple device: a chamber containing titanium plates coated with precious-metal oxides, with electrical current passing through. As salty pool water flows through the chamber, the current splits sodium chloride into sodium hydroxide and chlorine gas. The chlorine dissolves into the water as hypochlorous acid, the same active sanitiser as in a chlorine pool.
What makes SWGs different from a “salt water pool” marketed product is that you understand the chlorine generation is happening. The salt is fuel. The cell is the engine. The output is chlorine, regulated by how hard you push the cell.
How the chemistry works
The cell receives a low-voltage DC current (typically 20–40A at 6–8V). As pool water flows over the plates, two reactions happen:
- At the cathode (negative plate): water reduces to hydrogen gas + sodium hydroxide.
- At the anode (positive plate): chloride ions oxidise to chlorine gas, which immediately dissolves into the water.
The byproduct of this, sodium hydroxide, is what causes saltwater pool pH to drift upward. It’s also why salt cells naturally compensate against acidity in the water.
Hypochlorous acid (HOCl) and hypochlorite ion (OCl⁻) are the active sanitisers, exactly as in a chlorine pool. There is no chemistry difference between the chlorine that a salt cell generates and the chlorine that comes from a bottle of liquid pool chlorine.
Sizing your SWG
Cells are rated in “pool size capacity” or “chlorine output per day”. Both metrics measure the same thing: how much chlorine the cell can produce in a 24-hour run at 100% output.
| Pool size | Cell output rating | Australian models |
|---|---|---|
| Up to 30,000 L | 0.5–0.7 kg Cl/day | Hayward T-Cell-3, Pentair IC15 |
| 30,000–50,000 L | 1.0–1.2 kg Cl/day | Hayward T-Cell-9, Pentair IC20, Astralpool VX7 |
| 50,000–80,000 L | 1.5–1.8 kg Cl/day | Hayward T-Cell-15, Pentair IC40, Astralpool VX9 |
| 80,000–120,000 L | 2.0–2.5 kg Cl/day | Pentair IC60, Astralpool VX11, Zodiac eXO iQ |
Rule of thumb: oversize the cell by 30% beyond your pool’s calculated demand. A 50,000 L pool that needs 1.2 kg/day should use a 1.6 kg/day cell. The reasons:
- Cell output drops 30–50% over its life as plates wear.
- Summer peak demand is higher than year-average demand.
- Running a cell at 60% output extends its life vs running at 100% constantly.
Operating settings
Most cells have an output percentage setting (10–100%). The output controls how long the cell actively generates chlorine each run hour vs idling between generation cycles.
| Conditions | Typical output setting |
|---|---|
| Summer peak, heavy bather load | 70–90% |
| Summer normal | 50–70% |
| Spring / autumn | 30–50% |
| Winter (water below 18°C) | 10–30% |
The cell runs only when water flows. So a 60% output setting with the pump running 8 hours per day = 60% of 8 hours = 4.8 hours of active chlorine generation per day. If FC is dropping faster than 4.8 hours of generation replaces, either increase output, increase pump run time, or both.
Cell maintenance basics
Annual acid flushing is essential for cell life. The procedure is covered in detail in our salt cell maintenance guide. Skip it and expect to replace your cell at 3 years instead of 7.
Common SWG operational issues
- “Low Salt” warning despite correct salt, scale on plates causing low electrical conductivity reading. Acid flush.
- Cell producing no chlorine, check salt, check CYA, then check plates for wear.
- Cell makes too much chlorine, reduce output percentage or pump run time.
- Cell runs but no chlorine in water, pump isn’t actually pushing water through cell. Check pump prime and flow rate.
Sources & references
- Trouble Free Pool, ABCs of Pool Water Chemistry
- ANSI/APSP-11, Water Quality Standards in Public Pools
- AS 3633-1989, Private swimming pools (Australian Standard)
Frequently asked questions
How does a saltwater chlorine generator work?
Pool water containing dissolved salt flows through the cell, where electrical current splits the salt (NaCl) into sodium hydroxide and chlorine gas. The chlorine dissolves into the water as the same active sanitiser (hypochlorous acid) found in chlorine pools. Salt isn’t consumed, it’s recycled through the cycle.
What size SWG do I need for my pool?
Size by daily chlorine demand, then oversize by 30%. A 50,000 L pool typically needs a cell rated 1.5–1.8 kg of chlorine per day output. Oversizing accounts for cell wear, summer peak loads, and the option to run at 60% for cell longevity.
How long does a salt chlorinator cell last?
3–7 years depending on water hardness, run hours, salt management, annual maintenance, and cell quality. Soft water + good maintenance = 7 years. Hard water + neglected = 3 years.
Can I leave my SWG running all the time?
No. The cell runs only when the pump runs. Set pump runtime to match your daily chlorine demand (typically 6–10 hours/day in summer for a 50,000 L pool) with cell output percentage adjusting for seasonal demand.
Does the Water Test Calculator app help with SWG operation?
Yes. The app tracks chlorine generation vs demand, recommends cell output settings based on pool conditions, and prompts cell maintenance schedules. Launching on iOS and Android in approximately 10 days.
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