A magnesium pool is a swimming pool sanitised with a blend of magnesium chloride and potassium chloride instead of ordinary pool salt. A chlorinator turns those minerals into a small, steady supply of chlorine, so the pool needs roughly half the chlorine of a traditional pool. The result is soft, silky water with little chlorine smell, fewer red eyes and less dry skin.
Switching is simpler than most owners expect. Any pool type can be converted without a new shell, pump or filter, from backyard pools to commercial swimming pool systems at hotels, gyms and aquatic centres, and the upkeep follows the same rhythm as a saltwater pool with one extra monthly check. Understanding how the system works, what it costs and how to care for it makes the switch easy and keeps mineral water clear and safe.
Key Takeaways
- Magnesium pools use magnesium and potassium chloride in place of ordinary salt, cutting chlorine use by about half.
- They still need a small chlorine residual, as minerals alone cannot disinfect the water.
- Most pools run best at 3,000 to 5,000 ppm minerals, and 1 kg per 1,000 litres adds about 1,000 ppm.
- Converting usually costs a few hundred dollars in minerals, plus a compatible chlorinator if yours isn’t rated for them.
- Test chlorine and pH weekly, and minerals and metals monthly, to keep the water soft and stain-free.
What Is a Magnesium Pool?
“Mineral pool” is the category. A magnesium pool is the most common type within it, named after its main mineral.
A typical magnesium pool mineral blend contains:
- Magnesium chloride, the same compound found in seawater and bath flakes, which gives the water its soft feel
- Potassium chloride, which adds conductivity and supports the chlorinator
- Little or no sodium chloride, depending on the product
Quality blends are mostly magnesium and potassium. Cheap products padded out with regular pool salt deliver a weaker result, so always check the label for the mineral breakdown.
Magnesium pools are not chlorine-free. They are reduced-chlorine pools where the minerals improve comfort and water clarity, while chlorine still does the disinfecting.
How Magnesium Pools Work
Understanding the chemistry makes maintenance far easier.
- Minerals dissolve into the water. The blend is added until the water reaches its target mineral level, usually 3,000 to 5,000 ppm (parts per million). For comparison, the ocean sits around 35,000 ppm.
- The chlorinator generates chlorine. As water passes through the chlorinator cell, an electrical current splits the chloride in the minerals and produces chlorine. This is the same process a saltwater pool uses, just with a different mineral source.
- Chlorine sanitises, then reverts. Chlorine kills bacteria, viruses and algae, then breaks back down into chloride. The cycle repeats, which is why minerals are not “used up” by sanitising.
- Magnesium helps clarity. Magnesium forms fine particles that clump with impurities, helping your filter catch them. Many owners pair mineral pools with glass filter media for extra polish.
Because the chlorine is produced in small, constant amounts rather than heavy manual doses, the water never spikes into that harsh, stinging zone.
Magnesium vs Chlorine vs Saltwater Pools
| Feature | Magnesium pool | Saltwater pool | Traditional chlorine pool |
| Sanitiser source | Magnesium and potassium chloride | Sodium chloride (salt) | Liquid, granular or tablet chlorine |
| Chlorine level | About half the standard level | Standard, self-generated | Standard, added manually |
| Water feel | Soft and silky | Mildly salty | Can feel harsh |
| Chlorine smell | Barely noticeable | Low | Often strong |
| Eye and skin irritation | Minimal | Low to moderate | Common |
| Corrosion risk | Lower than salt | Higher on metal fittings | Low |
| Running cost | Slightly higher | Low | Low to moderate |
| Equipment | Chlorinator (mineral compatible) | Salt chlorinator | Dosing or manual |
The key difference between a magnesium pool and a saltwater pool is the mineral, not the machinery. Both generate their own chlorine. Swapping sodium chloride for magnesium and potassium chloride changes how the water feels and lowers the chlorine needed.
Benefits of a Magnesium Pool
The biggest draw is how the water feels, but the advantages go well beyond comfort.
- Softer, gentler water. The water feels like a mineral bath rather than a chemical one.
- Less chlorine exposure. With around half the chlorine, swimmers notice less eye stinging, fewer itchy patches and no tight, dry skin after a swim. Blonde hair is also far less likely to turn green.
- Little to no chlorine smell. The “pool smell” people dislike comes from chloramines, which form when chlorine reacts with sweat and sunscreen. Lower chlorine levels mean fewer chloramines.
- Clearer water. The natural flocculating effect of magnesium helps the filter trap fine particles, giving water a sparkling look.
- Kinder to equipment and surfaces. Mineral water is less corrosive than high-salt water, so it is easier on ladders, pumps and heaters.
- A more relaxing swim. Magnesium plays a role in hundreds of processes in the body, including muscle and nerve function, which is why it has long been used in therapeutic baths. Many owners find it more comfortable, although a pool is not a medical treatment.
- Compatible with automated chlorination. Waterlink’s Envirogen system can support magnesium pool operation with programmable timers, automatic pH control and chlorine monitoring, depending on the configuration, helping operators manage changing bather loads.
For families, people with sensitive skin and anyone who swims often, these benefits add up to a pool that feels better every time.
Drawbacks to Consider
No pool system is perfect, so it helps to know the trade-offs upfront.
- You still need some chlorine. Minerals alone cannot disinfect fast enough, so a small chlorine or bromine residual is always required.
- Slightly higher running costs. Mineral blends cost more per bag than standard pool salt. Tight chemistry closes most of that gap.
- Possible staining from metals. Despite “stain-free” marketing, high copper or iron in fill water can cause green or brown stains. Testing for metals and using a sequestrant prevents this.
- More frequent testing. Mineral levels should be checked monthly, compared with every few months for many saltwater pools.
- Bather load affects maintenance. Pools with more swimmers need closer monitoring of sanitiser levels and water balance, as sweat, sunscreen and other contaminants increase treatment demand.
For most owners, the softer water is well worth these small trade-offs.
How Much Does a Magnesium Pool Cost?
New pools: Choosing magnesium sanitisation at installation usually adds little or nothing to the build price, as the same shell, pump and filter are used.
Conversions: Mineral blends typically cost $30 to $60 per bag, depending on size and brand. A standard family pool generally needs several bags to establish, so most DIY conversions land in the range of a few hundred dollars. If your current chlorinator is not mineral compatible, budget for a replacement cell or unit.
Ongoing costs: Expect running costs a few dollars a week above a traditional chlorine pool. Minerals are only lost through splash-out, backwashing and rain overflow, not evaporation, so top-ups are needed a few times a year.
Pool size drives cost more than anything else. A small plunge pool of around 6,000 litres needs a fraction of the minerals of a 50,000-litre family pool, making magnesium an especially affordable upgrade for plunge pools and spas that run year-round.
How to Convert Your Pool to Magnesium
Concrete, fibreglass and vinyl pools can all be converted. Fibreglass is particularly well suited because its non-porous gelcoat does not react with minerals.
Step 1: Check your equipment
Confirm your chlorinator is rated for magnesium minerals. Many modern units are. If you use a sand filter, consider switching to glass media at the same time for better clarity.
Step 2: Lower existing salt and sanitiser levels
If converting from saltwater, partially drain and refill to dilute the sodium. Then let free chlorine drop to about 0.5 ppm or lower (bromine to about 1 ppm) before adding minerals.
Step 3: Test fill water for hardness and metals
Take a sample to a pool shop or use a quality test kit. High copper causes green staining, so add a metal sequestrant if needed. Using a hose pre-filter when topping up helps keep metals out.
Step 4: Balance the water
Adjust in this order, as each step affects the next:
| Parameter | Target range |
| Total alkalinity | 80 to 120 ppm |
| pH | 7.2 to 7.6 (ideal 7.4 to 7.6) |
| Calcium hardness (fibreglass, vinyl) | 175 to 225 ppm |
| Calcium hardness (concrete) | 200 to 275 ppm |
| Stabiliser (cyanuric acid, outdoor pools) | 30 to 50 ppm |
Step 5: Add the minerals
With the pump running, broadcast minerals around the pool perimeter and brush to help them dissolve. Keep the pump running for 24 hours and avoid switching on the chlorinator until the minerals have fully dissolved. Undissolved minerals that settle on the floor should be brushed, not vacuumed to waste.
Step 6: Restart the chlorinator and set sanitiser levels
Turn the chlorinator back on and set output so free chlorine sits around 1 to 2 ppm in daily use. Test after 48 hours and adjust gradually.
Step 7: Backwash after two weeks
A backwash after the first fortnight clears any remaining fine mineral residue from the filter.
Other ways to add minerals
Without a chlorinator, minerals can be delivered through an in-skimmer basket, floating dispenser or in-line cartridge, paired with a low chlorine or bromine source.
How Much Magnesium Mineral Do You Need?
A simple rule: 1 kg of mineral in 1,000 litres of water raises mineral levels by about 1,000 ppm.
Amounts below are approximate, starting from 0 ppm. If your pool already has some salt or minerals, subtract the current reading before calculating.
| Pool volume | To reach 3,000 ppm | To reach 4,000 ppm |
| 6,000 L (plunge pool) | 18 kg | 24 kg |
| 10,000 L | 30 kg | 40 kg |
| 30,000 L | 90 kg | 120 kg |
| 50,000 L | 150 kg | 200 kg |
| 70,000 L | 210 kg | 280 kg |
Follow your product label and chlorinator’s recommended range. Add minerals in stages, retest, then top up. Over-dosing can only be fixed by draining.
Example: A 50,000-litre pool reading 2,500 ppm that needs to reach 4,000 ppm requires about 75 kg (1,500 ppm × 50).
Magnesium Pool Maintenance
A consistent routine keeps mineral water soft, clear and safe.
Weekly
- Test free chlorine (1 to 2 ppm) and pH (7.2 to 7.6)
- Empty skimmer and pump baskets
- Brush walls and vacuum debris
- Check the water level, especially after rain or heavy use
Monthly
- Test mineral salinity and top up if it has dropped below your target
- Test total alkalinity and calcium hardness
- Check stabiliser levels on outdoor pools
- Backwash or clean the filter as pressure rises
Every three to six months
- Inspect and clean the chlorinator cell, removing any white scale with a cell cleaner
- Test for metals, particularly after a large refill
After heavy rain or a big top-up
Fresh water dilutes minerals. Retest salinity and pH, then rebalance before the chlorinator output drops.
Common problems and fixes
| Problem | Likely cause | Fix |
| Cloudy water | Low chlorine, high pH or a dirty filter | Rebalance pH, shock if needed, clean filter |
| Green or brown stains | Copper or iron in the water | Add a metal sequestrant, use a hose pre-filter |
| Chlorinator warning light | Low mineral level or scaled cell | Test salinity, clean the cell |
| Algae | Free chlorine too low | Raise chlorine output, brush and shock |
| Scale on tiles | High pH or calcium hardness | Lower pH, partially dilute with fresh water |
Is a Magnesium Pool Right for You?
If water comfort matters to you, a magnesium pool may be worth considering. Magnesium mineral blends can give the water a softer feel, although equipment compatibility and running costs depend on your pool system. Keeping minerals within the recommended range and regularly testing chlorine and pH helps maintain balanced water.
At Waterlink, we can help you explore compatible pool equipment and water treatment options. Contact us to discuss your pool’s requirements and find out whether a magnesium pool is right for you.
Frequently Asked Questions
1. Can You Mix Different Brands of Magnesium Pool Minerals?
Do not assume different mineral blends are interchangeable. Products can contain different proportions of magnesium, potassium and sodium chloride. Before changing brands or mixing products, check that the new blend is approved for your chlorinator and follow its dosing instructions.
2. Can a Standard Pool Test Kit Measure Magnesium Levels?
A standard pool test kit may measure chlorine, pH and other water parameters without measuring magnesium separately. Total hardness readings can also include magnesium, making them different from calcium hardness readings. Use a magnesium-specific test or ask a pool professional familiar with mineral systems to interpret your results.
3. Why Is There White Foam After Adding Pool Minerals?
Some magnesium mineral systems can produce temporary white froth during initial dosing as the minerals dissolve and the water settles. Keep the pump running according to the product instructions. The froth should usually disappear within a few hours or overnight. If it persists, have the water and filtration system checked.
4. Can You Still Use Pool Minerals That Have Clumped in the Bag?
Clumping can happen when magnesium minerals absorb moisture from the air. It does not necessarily mean the product is unusable, although the clumps may dissolve more slowly. Follow the supplier’s instructions, maintain circulation and brush any settled minerals to prevent concentrated deposits on the pool floor
5. Can Magnesium Pool Backwash Water Be Used on the Garden?
It depends on the mineral blend and the manufacturer’s instructions. Some sodium-free systems allow garden reuse after dilution, but this advice should not be applied to every mineral pool. Check the product’s requirements and local wastewater rules before using backwash water on plants.
6. Does a High Total Hardness Reading Mean There Is Enough Calcium?
Not necessarily. Magnesium contributes to total hardness, so a high reading can mask insufficient calcium. Ask for a calcium-specific test or the testing method recommended for your mineral system before adjusting calcium levels. This helps you avoid treating the wrong water balance problem.