Stains in the spa shell? 4 common reasons why and how to fix

Have you noticed stains on your spa pool or swim spa’s shell? In this article, we’ll help you figure out what causes stains in your spa shell, how to remove them, and how to prevent them from happening again.

Why is my spa stained?

Generally speaking, four principal offenders cause stains in the spa shell. They are:

  • Minerals. Minerals such as calcium and magnesium, typically found in hard water can deposit as white or off-white scales on your spa shell.
  • Rust. While spa shells are typically made with acrylic, there are plenty of metal parts in spa pools and swim spas. These parts can develop rust over time when not protected.
  • Scum. Scum typically develops around the waterline and is caused by the build-up of oils, grease, sunblock, and other chemicals in your spa.
  • Metals. High levels of certain metals such as iron, manganese or copper can also cause discolouration in your spa shell.

How do I prevent stains in the spa shell?

The best way to prevent stains from coming back is by taking care of your spa shell. Much like any other component, your spa shell will require regular cleaning and maintenance throughout its lifetime.

Here are a few steps you can take to keep your spa shell in excellent condition.

  • Start by wiping down the inside of your spa every 2 to 3 weeks. You can do this without draining your spa water.
  • Change your water every 4 to 6 months for spas and every 12 months for swim spas.
  • Clean the spa shell while the water is drained following the recommendations above.
  • Keep your spa water sanitised and balanced.
  • Avoid using sunblock, lotion, or other skincare products when soaking in your spa. We also suggest you rinse off before you enter the spa.
  • Use a spa water clarifier product that can help remove oils and fats which cause scum. A water clarifier can also help counteract metal content in your water (such as copper) which can cause stains.
  • Test and adjust your calcium hardness levels. Add a calcium raiser product and a spa water softener if your calcium levels are too low.

How do you remove stains from spa shells?

Stains on spa shells may be caused by a variety of things, but removing them generally involves a similar process. In many cases, you can even use similar products to deal with them.

With that said, we do caution you to use any chemical or cleaning product only as directed by the manufacturer.

Once you determine the cause of the stains in your spa shell, follow these steps to remove them.

Test the water

Use test strips to check the pH and alkalinity levels of your spa. If you get your hands on Poppit® 4 Way Test Strips or BioGuard Test Strips 6 in 1, you can also use them to check the calcium hardness of your spa water. If you’re having trouble reading test strips, a good alternative is to use a Spa Water Test Meter / Digital pH tester.

Use spa shock

This will break down waste and organic contaminants which cause odour and cloudy water. Once treated with spa shock, water quality and clarity are usually completely restored. The article below can guide you on how to use spa shock properly.

Add a water clarifier

This can help reduce metal and mineral content in your spa water which can contribute to staining.

Clean pipes

Using a pipe degreaser or a line flush product, you’ll next want to clean out the plumbing of your spa. The guide below can help you clean your spa pipes and plumbing system effectively.

Turn off the spa and breaker

Once done cleaning the pipes, the next step is to turn off the spa as well as the breaker. This will ensure that the spa will not be receiving any electricity to keep you safe when you start scrubbing the stains in your spa shell. Please refer to your spa’s owner’s manual for instructions.

Drain the spa water

Next, you want to drain the spa water completely. Check out the article below for a step-by-step guide on how to drain your spa pool or swim spa.

Clean your spa

Once your spa is completely drained, you can start scrubbing the stains thoroughly. Use the correct cleaning product for the type of stain you’re trying to clean and be sure to only use scrubs or wipes that will not scratch the surface of your spa shell.

For the best techniques, recommended products, and an in-depth guide on how to clean your spa shell, check out the article below.

Use a polish & protection product

Clean the filter

If your spa is stained, chances are your filter may need cleaning or replacement. Refer to the article below for a more detailed guide on how to clean a spa filter.

Rinse the shell

Once you’re sure that any stain, dirt, or grime is taken care of, it’s time to rinse out the shell. You’ll want to be really thorough at this step because cleaner residue can cause a foaming problem which may make you have to start over. Keep an eye out for any remaining stains to make sure you got them all.

Dry the spa

Wipe down the fixtures and areas around the spa that will not be filled with water such as the cabinet.

Refill the spa

Start filling the spa and make sure to use a hose filter if your source water has high levels of minerals or metals. Doing this will help avoid future stains caused by hard water.

Balance the water and sanitise

Once the spa is full, start your usual water maintenance routine using your preferred spa chemical products. If you’re not sure which products are needed, you can refer to the article below.

Test your calcium hardness levels

If you have been getting white scale staining around the water line in your spa shell, this could indicate your calcium levels are incorrect. Read the detailed guide on this


You are now ready to start soaking again.

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What can you use to clean the spa shell?

Wondering what products to use to clean your spa shell? Here’s a list of items you need:

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In Summary

Stains in the spa shell are typically caused by the build-up of minerals, metal, rust, or scum. The best way to deal with it is to conduct a thorough cleaning with the spa water drained.

To prevent this, make sure to keep a regular cleaning and maintenance schedule for your spa. You also want to keep your spa water sanitised and balanced to avoid the build-up of mould, mildew, or white scales.

We hope this article has helped you learn more about stains in your spa shell. Got more spa-related questions? Feel free to get in touch and one of our experienced spa experts will help you find what you need.

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DISCLAIMER: The following registered trademarks are owned by companies not affiliated in any way with Spa World or Vortex Leisure Pty Ltd – the parent company of Spa World:

Poppit® trademark is owned by Waterco. BioGuard BioGuard is a trademark of BioLab Australia Pty Ltd.

Affiliations: Vortex® Spas, Fisher™ Spas, and Spa World™ are trademarks owned by Vortex Leisure Pty Ltd.

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