Total Dissolved Solids in a spa- What is it? How to reduce TDS

Finding it hard to keep your water clear? TDS could be a problem in your spa. In this article, you'll learn what total dissolved solids in a spa is and more.

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Spa or hot tub owners often take their water maintenance for granted and don't give much thought to the Total Dissolved Solids (TDS) level. The higher the TDS level, the more difficult it is for the spa or hot tub to operate at peak performance.

Not only will it reduce the spa's or hot tub's lifespan, a high TDS level can also cause problems with water clarity, contribute to skin irritation, and make it harder to keep your water crystal clear.

In this article, you'll learn:

What are TDS (total dissolved solids) in a spa pool?

Ever wondered about total dissolved solids (TDS) in a spa or hot tub? TDS play a significant role in the quality of your spa water and can affect the experience bathers in your spa will have.

TDS refers to any dissolved matter that can buildup over time in spa water. TDS can include organic matter, salts, minerals, metals, residue from chemical products. Residues from chemical products can include calcium, magnesium, bicarbonate, sodium, potassium and others.

Note that oils from beauty products, suntan lotion and human bodies are not considered TDS as they are not dissolved in the water, even though these can also cause issues with water quality.

Some dust and debris particles can appear to be dissolved in the water, but can actually be filtered out by an effective filtration system that is well maintained.

What should the TDS (total dissolved solids) level be in a spa or hot tub?

The level of total dissolved solids should be less than 1500ppm in your spa, swim spa or hot tub. If it is at 1500ppm or higher, you will need to take one of the steps below.

Note that if you are using a salt-based system (sodium chloride), the salt component in your water may contribute to the TDS reading.

symptoms of high TDS in spa or hot tub

What are the symptoms of high TDS in my spa?

If you are experiencing any of the following issues in your spa or hot tub, it may be due to high total dissolved solids (TDS).

  • Eye and skin irritation
  • Difficulty keeping your water balanced
  • Using more chlorine or bromine sanitiser to keep your water clear
  • Excessive foam
  • Smell
  • Filters need cleaning more often
  • Cloudy water
  • A greenish or brown tint in your water (a sign of algae growth)
  • Water that tastes salty
  • The presence of high mineral content in your spa water can cause components in your spa and plumbing system to corrode faster.

How to reduce TDS (total dissolved solids) in my spa?

Reducing the TDS in your spa or hot tub is not just a matter of cleaning it more often. Your spa water chemistry revolves around pH, total alkalinity and calcium hardness levels. But TDS should not be overlooked when it comes to water quality.

If you're looking to manage the TDS level in your spa or hot tub, here are a few steps you can take;

  1. Ensure you are sanitising your water regularly with chlorine sanitizer
  2. Make sure your water is balanced correctly. Use test strips to test the pH and alkalinity of your spa or hot tub before and after every use to make sure that it is at the correct level.
  3. Use a water clarifier to neutralise any impurities in your spa water, enabling them to be caught by your filter and removed when you clean your filters.
  4. Use a scum buddy to absorb excess oils in your spa water. Remove and rinse regularly.
  5. Add a water softener product if your water is hard or high in calcium content
  6. Soak your spa filters regularly with an approved filter cleaning solution to trap particles and bacteria.
  7. Partially drain and refill your spa with fresh water (this will dilute the TDS level)
  8. Completely empty and refill your spa*
  • Remember that when refilling with fresh water, the fill water may also contain some minerals and pollutants. Tap water for example will often contain mineral content and traces of chlorine and flouride that has been used by your local council or city to treat the water. You should test your water again after.

Click the button below to learn a step-by-step guide on how to fill your spa pool or swim spa with water.

Do high TDS in my spa make my chemicals work harder?

High TDS levels in your water can make your sanitising chemicals work harder to keep your water clear.

The reason for this is that the TDS levels make it harder for the sanitising product to generate the chemical reaction that oxidises (burns up) organic matter in your spa. This means you'll need a higher amount of chemicals to maintain your water clarity leading to increased environmental impact and cost.

How do I test TDS levels in my spa?

To test your spa water for TDS levels, you will need a TDS test kit, or you can take a water sample to your local pool store and get them to test it for you.

Testing the TDS levels in a spa can be helpful in determining the level of water hardness and the potential need for water treatment. There are a variety of ways to test the TDS levels, including using a digital or point-of-use (POU) meter. There are also some test strips available that will give you a reading - but they are not particularly accurate and mostly just measure salt levels in your water.

If the TDS levels are above 500 parts per million (ppm), then the spa may require treatment. If your TDS level is over 1500 ppm, then you will need to partially or fully drain the spa and refill it with fresh water. Then test the water again.

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How long between water changes in my spa?

This can depend on a lot of factors, such as the type of spa, the size of the spa (spa volume), and the bather load. Bather load refers to how often you use the spa and how many people are in the spa.

Typically you should change your spa water every 4-6 months for a portable spa 700 - 4000L (175 - 1000 gallons) and every 12-18 months for a swim spa - 4000L or larger. (1000 gallons +)

If you notice your water quality is deteriorating it may be time to change your spa water.

Draining your spa is relatively straightforward. View our detailed guide on how to empty and refill your spa.

What should I do if my spa has hard water?

If your spa has hard water, it is important to take steps to remedy the situation.

Hard water can cause poor pH balance, mineral buildup, and increased chlorine usage. By correcting the pH balance, you will help to restore the water's natural clarifying and disinfecting properties. You can do this by using a water softener or by adding a natural acidifier.

Finally, it is important to keep the spa clean and free of debris to ensure that the water is properly disinfected.

To learn more about hard spa water, please click the button below.

Can I use borax in a hot tub or spa?

While it is possible to use Borax in a hot tub or spa pool, it is not recommended as it is not a good idea to expose the hot tub to salt. If you do choose to use Borax in your spa or hot tub, you do so at your own risk.

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Got more questions?

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