Salt chlorinators: salt levels and cleaning the cell

Illustration.

How it works

HealthyWA describes salt water chlorination as the most common way home pools in WA are disinfected: an electric current through salty water, via electrodes in the cell, makes chlorine. In heavy use or hot weather a domestic chlorinator may not make enough, and the water can turn milky; then you add chlorine by hand to catch up.

How much salt

Every chlorinator has its own target salt range, printed in its manual and often on the unit. Test the salt, then add the difference: 1 mg/L is 1 gram per 1,000 litres, so lifting a 50,000 L pool by 1,000 mg/L takes 50 kg of pool salt. Calculate yours. Add it in the shallow end with the pump running and brush until it dissolves.

Cleaning the cell

White scale builds up on the electrodes, especially with high calcium, and cuts how much chlorine the cell makes. Many newer units self-clean; others need cleaning by hand as the maker directs, usually by soaking the cell in a weak acid solution made up exactly as the manual says. Wear eye protection and gloves, and always add acid to water.

Maple's tip

Rain dilutes salt. After a big downpour, retest the salt before your chlorinator starts warning you.

Setting the output

A salt chlorinator only makes chlorine while the pump runs. Set the output and the pump hours together so free chlorine stays in range. In summer, with warm water, sun and swimmers, you will usually need a higher output or longer run time; in winter, less. Many units have a boost or superchlorinate button for after heavy use or rain. Test free chlorine regularly and adjust the output rather than relying on the dial alone.

Common faults

• Low salt warning: test the salt; rain and backwashing lower it. Add salt only after testing.
• High salt warning: usually after adding too much; dilute with fresh water.
• Low or no chlorine output: check for scale on the cell, low salt, cold water (many cells produce less below about 15 degrees), or an ageing cell.
• Flow error: check the pump, the baskets and the filter; the cell will not run without flow.
• Cell near end of life: cells wear out after a number of years of use; output falls even when clean.

Cold weather

In cold water, many chlorinators produce less chlorine and some cut out to protect the cell. Chlorine demand is also lower in winter, so a lower output and shorter run time usually suit, but keep testing; a winter pool can still turn green.

Salt and the pool surrounds

Salt water can corrode metal and some stone and grout around a pool over time. Rinse metal fittings and pavers with fresh water now and then, seal suitable stone surfaces, and use pool fittings designed for salt water.

When to replace the cell

A cell that stays clean but cannot hold chlorine at full output, even with correct salt and warm water, is probably near the end of its life. Many units show cell hours or a cell-life warning. Replacement cells must match the chlorinator model.

Types of pool salt

Use salt made for pools: fine, dry and free of additives such as anti-caking agents or iodine, which can stain or cloud the water. Mineral blends for magnesium pools are a different product with their own target levels. Add salt to the pool, not the skimmer, broadcast around the shallow end with the pump running, and brush any that settles until it dissolves. Retest after a day of circulation before adding more.

Salt pools and pH

Salt chlorinators raise pH as they make chlorine, so salt pools usually need regular acid additions. Some chlorinators can be fitted with automatic pH control. Test pH at least weekly in summer: see how to raise or lower pool pH.

Is a salt pool cheaper to run?

A salt pool saves on buying chlorine, but adds the cost of the chlorinator, replacement cells over the years, salt top-ups and the electricity to run the cell. Many owners find it about the same overall but far more convenient.

Our short answer

Keep salt in your chlorinator's target range, clean the cell when it scales, set output and pump hours to hold free chlorine, and test pH often because salt pools drift high.

Testing salt

Test strips, digital salt meters and pool shop tests all measure salt. Many chlorinators also display a salt reading, but it can drift as the cell ages, so check it against a separate test now and then. Test after heavy rain and after topping up the pool, because both dilute the salt.

How much salt to buy

Work out the pool's volume, the difference between the current and target salt levels, and multiply: each 1,000 mg/L increase needs 1 kg of salt for every 1,000 litres. Buy a little extra, add three-quarters of the calculated amount first, and retest after it has dissolved.

Super-chlorinating with a salt pool

After a party, heavy rain or the first signs of algae, use the chlorinator's boost function or add liquid chlorine to raise free chlorine quickly. A chlorinator alone can take a long time to lift chlorine far enough to deal with algae, so liquid chlorine is the faster fix for a green salt pool.

Starting a salt chlorinator

When filling a new pool or converting to salt, add salt to the chlorinator's target, let it dissolve fully with the pump running, set a medium output, and test free chlorine daily for the first week, adjusting output and pump hours until chlorine holds in range. Balance pH and add stabiliser for an outdoor pool at the same time.

Salt chlorinator lifespan

The control box usually outlasts the cell. Cell life depends on hours of use, output setting, water balance and how gently it is cleaned. Keeping pH and calcium in range so scale forms slowly, and avoiding very frequent acid washes, helps a cell last longer.

Common questions