Can you put magnesium in a spa? (Warnings, top tips and more)

Magnesium is hailed as a mineral that provides many health benefits to the body such as healthy bones and boosting energy levels. Many people choose to add magnesium sulphate, also known as Epsom salts to bath water because of its healing properties.


So, can you add magnesium to a spa pool or swim spa? In this article you will learn why not to add magnesium or Epsom salts to your spa water and what magnesium-containing products are safe to use in spa pools.

Disclaimer - In this article we’ve used brand names not affiliated with Spa World™ or Vortex Leisure Pty Ltd, the parent company of Spa World™. All information including pricing and product details, was accurate at the time of writing and may change without notice.

What is magnesium?

Magnesium is a mineral and the human body relies on it in many ways to function. This includes oxygenating the body, relieving the nervous system and relaxing sore muscles.

According to Dr Kyle Neely, a physical therapist and certified strength and conditioning coach, a large percentage of humans are magnesium deficient. Decreased oxygenation in the body can lead to negative feelings such as tiredness and lower energy.

However, there are ways to increase levels of magnesium in the body such as including foods in your daily diet that contain higher levels of magnesium. You can also take supplements that contain magnesium.

Can you put magnesium in a spa?

In short, no. You should not add magnesium in the form of magnesium sulphate or Epsom salts to your spa pool or swim spa. If salt levels in the water exceed the recommended amount, important parts in a spa may start to corrode.

Spa components such as the heater element or parts of the pump cannot tolerate high levels of salt in the water. In fact, salt levels above 1500 ppm (parts per million) can cause permanent damage to a spa, depending on the pH of the water.

The good news is that there are some very good products such as MagnaSpa that contain magnesium but with a salt content that’s low enough to be harmless to your spa.

Important: If you choose to use MagnaSpa, it is to be used in addition to an approved sanitiser, it does not replace the need for spa sanitiser.

Watch: Can you put magnesium in a spa?

What is MagnaSpa and what are its benefits?

MagnaSpa is a water softener for spas and is designed to make the water feel silkier and more comfortable as you sit back and relax. The product is manufactured by Zodiac that supplies pool equipment and pool products.

MagnaSpa is made up of a blend of 50% magnesium chloride and 50% potassium chlorid. This makes the mix safe for your spa, soothing for sensitive skin types and allows you to soak up the benefits of both magnesium and potassium.

MagnaSpa vs MagnaPool – what’s the difference?

To put it simply MagnaPool is designed for swimming pools and MagnaSpa is designed for spas. According to the product manufacturer Zodiac, the ratio of minerals for pools and spas varies. MagnaPool contains a lower content of magnesium and is designed for cooler water and different sanitsers.

In comparison, MagnaSpa contains 50% potassium chloride and 50% magnesium chloride. This means there is around 60% more magnesium (by volume) in MagnaSpa than what you will find in MagnaPool.

What are the benefits of potassium chloride in spa water?

According to Zodiac, potassium chloride in water works as a strong relaxant and moisturiser for the skin.

Can I put Epsom salts in my spa pool?

epsom salt

No, Epsom salts should never be added to water in a spa pool or swim spa. Epsom salts contain magnesium sulphate which is an alkaline chemical compound. Overall, Epsom salts contain a high level of salt.

To achieve the health benefits from Epsom salts, the recommended level is 20,000 ppm which well exceeds the maximum level of 1500 ppm that spas can withstand.

To learn more about using Epsom salts, read this article - Are Epsom salts ok to use in spas? A warning for spa owners.

Do I still need to sanitise my spa after I add magnesium?

Yes, you will still need to add sanitiser to your spa or swim spa. MagnaSpa is compatible and can be used with all sanitising agents. If you’re wondering why you need to use sanitiser with MagnaSpa but not with MagnaPool, that’s because MagnaPool uses its hydroxinator to create the sanitiser required in a pool.

Can I turn my swim spa into a magnesium salt water spa?

Yes, you can turn a swim spa into a maganesum salt water spa. However, you can not use the Aquasal™ Salt System

The AquaSal™ Salt System (AQ) is an automatic sanitising system that converts salt to natural chlorine. While you can use magnesium to create chlorine, it will likely impact the salt reading in the Aquasal™ system by showing false readings. In turn, the system may read 'low salt' so it doesn't produce any salt. For this reason, you should not use Aquasal™ with magnesium salt.

Please note, AquaSal™ is only designed for use in swim spas.

Can I add magnesium to my chlorine free spa?

Yes, you can add MagnaSpa to a spa that uses chlorine-free hydrogen peroxide sanitiser.

Hydrogen peroxide is one of the most effective chlorine-free spa sanitisers however because it is an oxidiser, it is considered a ‘dangerous good’. Couriers need to handle this chemical compound separately from other goods so it could increase delivery cost and time.

Read this article to learn more about chlorine-free options for your spa pool.

Can magnesium affect components in a spa long term?

Yes, adding magnesium in the form of magnesium sulphate or Epsom salts to spa water can affect spa components if salt levels exceed 1500 ppm. Using a mineral product blend like MagnaSpa that contains magnesium chloride is a safe option because it is specifically designed for spa pools because of its low salt content. A magnesium containing product with a low salt content won’t harm your spa and offers the benefits of softer spa water.

What happens when minerals mix with magnesium?

When other minerals are added to magnesium, several changes can occur. According to Zodiac, hardness levels and salinity levels can increase. The minerals used in MagnaSpa are of food-grade and therefore do not add contaminants to spa water that can lead to staining.

Does magnesium affect the pH of the spa water?

MagnaSpa is pH neutral so it will not affect the water balance in a spa.

How much does MagnaSpa cost?

MagnaSpa is manufactured by Zodiac and packaged in a 3kg bag. One bag is suitable for 1000L so you may need to purchase another bag if you have a larger spa or a swim spa.

You can purchase MagnaSpa through SpaStore and it retails at NZ$52.65 (price accurate at the time of writing).

How long does magnesium last in a spa?

It is recommended that one bag of MagnaSpa per 1000l of spa water is added each time the spa is refilled.

Can magnesium be used with bromine-based spa chlorine at Spa World?

According to Zodiac, yes, spa pools that use bromine-based chlorine are compatible with MagnaSpa. There isn't any chemical reaction that forms unwanted by-products.

In Summary

When it comes to adding magnesium to your spa, using magnesium sulphate in your spa can cause more harm than good.

This article should give you peace of mind that if you use the right magnesium-containing product that is specifically designed for spa pool use, you will be able to soak up the benefits of this mineral, while keeping your spa components safe.

MagnaSpa can be purchased online at SpaStore.

Wondering what the best spa sanitising products are on the market? Learn more in this review article below.

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