Salt Water vs Magnesium vs Chlorine Pools: An Honest Comparison

Every pool needs sanitising — the question is what does the work and how the water feels while it happens. The three mainstream options are traditional chlorine, salt water chlorination, and magnesium (mineral) systems. They all keep water safe; they differ in feel, maintenance, and cost. Here's the honest comparison we give customers.

The short version

The key thing most people miss: salt and magnesium pools are still chlorine pools. The chlorinator generates chlorine from the dissolved salts — what changes is what else is in the water and how it feels on your skin.

How a salt water pool actually works

A salt chlorinator is a small electrolysis unit plumbed in after your filter. As water passes over the metal plates in its cell, a low electrical current splits dissolved sodium chloride into chlorine gas, which instantly dissolves and sanitises the water. After the chlorine has done its job it recombines back into salt, and the cycle repeats — which is why you only top up salt to replace what's lost to splash-out, backwashing and rain, not because the pool "uses it up".

Because chlorine is produced continuously while the pump runs, sanitiser levels stay far steadier than hand-dosing ever manages. That steadiness is most of why salt pools feel milder: the harsh "chlorine smell" people associate with pools is actually chloramines — the by-product of chlorine that's been overwhelmed, not chlorine itself.

Salt water pools

Salt chlorination has been the Australian default for two decades for good reason: low effort, low ongoing cost, and softer water than a manually dosed pool. The salt sits at roughly 4,000–6,000 ppm — about a tenth the salinity of seawater. You can taste it faintly, but it's closer to a teardrop than the ocean.

Salt water pool maintenance

"Mostly automatic" doesn't mean zero effort. A realistic salt pool routine looks like this:

• Weekly: test free chlorine and pH with strips or a test kit, and empty the skimmer basket. Salt cells push pH upward over time, so small acid additions are the most common correction.
• Monthly: check the salt level (most chlorinators display it) and top up if it's drifted below the maker's range — usually a bag or two after heavy rain. Check stabiliser (cyanuric acid) too; without it, Queensland sun destroys chlorine almost as fast as the cell makes it.
• Every 3–6 months: inspect the chlorinator cell for white calcium scale and clean it if needed. Many modern units are self-cleaning (they reverse polarity to shed scale), which stretches this out considerably.

The cell is the one genuine consumable: expect roughly 5–8 years of life before output drops and it needs replacing, typically a few hundred to around a thousand dollars depending on the model. Running the salt level too low is the fastest way to kill a cell early, so don't ignore the low-salt warning light.

The other trade-off is minor but worth knowing: constant salt splash can be tough on some soft coping stones, timber decks and salt-sensitive plants right at the water's edge.

Magnesium (mineral) pools

A magnesium pool runs the same chlorinator hardware with a mineral blend — predominantly magnesium chloride, usually with potassium chloride — instead of plain salt. The result is the silky, almost bath-like water people rave about, less chlorine smell, and water that many swimmers with sensitive skin or eczema find noticeably gentler. Owners also report less eye redness and softer hair and skin after swimming.

We install mineral-ready chlorinators as standard, and it's become our most requested water type. For the full picture — chemistry, costs, and what the science does and doesn't support — read our complete magnesium pool guide and magnesium pool benefits deep-dives.

How much magnesium do you add? Initial dosing for a typical 30,000L pool takes 8–12 bags of mineral blend (roughly $300–$450), then top-ups after backwashing, splash-out and rain — most owners spend $150–$300 a year. That's the honest premium over plain salt: about $100–$200 annually for meaningfully nicer water.

Any downsides to a mineral pool?

Two honest ones. First, the running-cost premium above — mineral blends cost more per bag than pool salt, and only pool shops stock them (you won't find every blend at the hardware store). Second, magnesium can throw a temporary cloudy haze if you dose a large amount at once or let pH drift high; dosing gradually through the skimmer with the pump running avoids it. Maintenance is otherwise identical to a salt pool — same testing, same cell care.

Traditional chlorine pools

Manually dosed chlorine still works and has the lowest hardware cost — there's just no automation. You're testing and adding chemicals weekly, the sanitiser level swings more between doses (that's the "chlorine smell" — chloramines from under-sanitised water), and holidays require a plan. We generally only recommend it where budget rules everything.

Converting between systems

Good news: nothing about the pool's plumbing changes between these three options, so you're never locked in.

Chlorine to salt water: install a salt chlorinator on the existing pipework (an hour or two for a pool technician), add the initial salt dose — roughly 10–12 bags for a typical 30,000L pool — balance the water, and you're done. All-up, converting typically lands around $1,500–$3,000 depending on the chlorinator you choose, and it pays itself back in chemicals you stop buying.

Salt water to magnesium: even easier. Most modern chlorinators handle mineral blends without modification — check your model's manual, or ask us. From there it's a gradual swap: as your salt level naturally falls through backwashing and splash-out, top up with mineral blend instead of salt. Within a season the water is predominantly magnesium. If you want the full effect immediately, a partial drain-and-refill with fresh dosing gets you there in a weekend for the cost of the bags (roughly $300–$450 on a typical pool).

Magnesium back to salt: the same process in reverse — just top up with plain salt instead. There's no penalty for trying minerals and changing your mind.

What about ozone and UV systems?

You'll occasionally see ozone generators or UV sterilisers marketed as "chlorine-free" alternatives. They're genuinely useful supplementary sanitisers — both destroy contaminants as water passes through the equipment — but neither leaves a residual sanitiser in the pool itself, so Australian conditions still require a chlorine residual in the water. In practice they're an add-on that lets a salt or mineral chlorinator run at a lower output, not a replacement for it. Worth considering; not a fourth category.

Salt, minerals and fibreglass: a perfect match

If you're weighing water types while planning a new pool, the shell material matters more than most people realise. Salt and mineral water are both fully compatible with fibreglass — and fibreglass actually suits chlorinated-salt systems better than concrete does. Concrete interiors are porous and mildly alkaline, which means algae footholds, higher chemical demand and salt slowly attacking the interior finish over the years. A fibreglass gelcoat is non-porous and chemically inert, so you run less chlorine, scrub less, and the surface shrugs off salt. The Aqua Technics shells we install carry a Lifetime Interior Surface Guarantee, and every MFP Easy pool includes a mineral-ready chlorinator, premium filtration and Pool School handover in the all-inclusive installed price — so you can start on salt and switch to minerals whenever you like.

Ongoing care is genuinely light either way — our fibreglass pool maintenance guide covers the full routine.

Which one should you choose?

• Want the nicest water and swim often? Magnesium. The running-cost premium is small against a $50k+ pool.
• Want set-and-forget with lowest running cost? Salt water.
• Building on the tightest possible budget? Manual chlorine works, and you can convert to salt or minerals later — the plumbing doesn't change.

Still unsure? This is exactly the conversation to have at a free site visit — book a chat and we'll match the system to how your family actually swims.

FAQs

Is a magnesium pool still a chlorine pool?

Yes — the chlorinator generates chlorine from the mineral salts, so the water is sanitised exactly as reliably as a salt pool. The magnesium is what changes the feel of the water, not the safety mechanism.

Can I convert my salt water pool to magnesium?

Usually yes, and easily — most modern chlorinators handle mineral blends. It's typically a matter of adjusting the water balance and replacing sodium chloride with a magnesium blend at the next top-up.

Do magnesium pools damage fibreglass?

No — mineral water is fully compatible with fibreglass shells. Fibreglass and magnesium are a popular pairing precisely because the smooth gelcoat plus soft mineral water gives the most comfortable swim available.

What's cheaper to run, salt or magnesium?

Salt, by roughly $100–$200 a year on a typical pool, because sodium chloride is cheaper per bag than mineral blends. Hardware and power costs are essentially identical.

What salt level should a salt water pool have?

Most chlorinators want roughly 4,000–6,000 ppm — check your unit's manual for its exact range. That's about a tenth of seawater, so the water tastes faintly saline rather than like the ocean. Too low and the cell can't make enough chlorine (and wears out faster); too high and you're wasting salt and risking corrosion on fittings.

How long does a salt water chlorinator cell last?

Typically 5–8 years. You'll extend its life by keeping salt in the recommended range, cleaning calcium scale off the plates every few months (or choosing a self-cleaning model), and not running the output higher than the pool needs.

Do I still need to test the water in a salt or mineral pool?

Yes — a quick weekly check of chlorine and pH, plus an occasional salt and stabiliser test. The chlorinator automates production, not water balance; pH in particular drifts upward in salt-chlorinated pools and needs small corrections.