How salt chlorinator size is worked out

Electrolytic Chlorine Generation

A salt chlorinator cell contains titanium electrodes coated with mixed metal oxides (typically ruthenium and iridium oxides). When DC current passes through saltwater flowing over these electrodes, the chloride ions (Cl⁻) are oxidised at the anode: 2Cl⁻ → Cl₂ + 2e⁻ The dissolved chlorine forms hypochlorous acid (HOCl), the main active sanitiser in pool water. Cell output is rated in grams of chlorine equivalent per hour, and our model matches this production rate to your pool's total chlorine demand.

Chlorine Demand Modelling

A pool's chlorine demand is the sum of all processes that consume free available chlorine: • UV photolysis: Solar radiation breaks down HOCl at a rate proportional to UV intensity and inversely proportional to CYA (stabiliser) concentration • Oxidation demand: Organic matter from bathers, vegetation, and airborne debris consumes chlorine through oxidation reactions • Combined chlorine formation: Nitrogen compounds (sweat, urine, cosmetics) react with chlorine to form chloramines • Dilution losses: Splash-out, backwashing, and rainfall dilute residual chlorine

• UV degradation rate modelled using Melbourne's latitude-specific solar irradiance
• Bather load contribution scaled by swimmer-hours per week
• Organic loading from surrounding vegetation and wind-blown debris
• Stabiliser (CYA) protection factor for UV-induced chlorine loss

Cell Sizing Algorithm

The sizing algorithm determines the minimum cell capacity (g/h Cl₂ output) that can maintain target free chlorine residual (typically 1 to 3 ppm) under peak demand conditions while operating within recommended duty cycle limits. Allowing spare cell capacity can reduce how hard the chlorinator needs to run, but the right size still depends on pool volume, demand, brand limits and run time. This longevity factor is built into our recommendations.

Salt Concentration & Conductivity

Electrolysis efficiency depends on the salt concentration in the pool water. Most cells have a required salt range, often around 3,000 to 6,000 ppm NaCl depending on the model. Below minimum threshold, current flow is insufficient for adequate chlorine production; above maximum, accelerated electrode corrosion occurs. Our model calculates initial salt dosing requirements based on pool volume and current salt level, and estimates ongoing salt replenishment needs from dilution events (rain, splash-out, backwashing).

Temperature & Seasonal Factors

Chlorine demand varies dramatically with water temperature. Warmer water can increase bacterial growth, swimming hours and chemical reaction rates, which raises chlorine demand. Conversely, cell output also increases with temperature due to improved electrolyte conductivity. Our model balances these opposing effects to recommend appropriate seasonal output settings.