How do I use test strips in my spa? (Test strips explained, how to read, how to adjust your water)

In this article, we’ll explain how to use test strips to test your spa water to ensure that it remains clear and clean.

We cover answwer to questions such as:

• Why do I need test strips in my spa?
• What are the best test strips for chlorine spa water?
• How do I use test strips in my spa?
• How do I Balance the Total Alkalinity in my spa water?
• Spa test strips frequently asked questions

Please note that the information in this article is for guidance purposes only. You should always follow the directions on your test strip or chemical containers.

Why do I need test strips in my spa?

Having your spa water pH and alkalinity set within the correct range is important. If the water pH is too high, this means your water is alkaline and can appear cloudy and be harder to sanitise.

If your pH is too low (outside of the ideal range between 7.2 and 7.6) then your water is too acidic - it can be corrosive on skin, eyes and componentry in your spa.

What are test strips for spa pools?

Test strips for spa pool water are small strips of paper or light card about ½ a centimetre wide and about 10cm long.

Test strips for spa pools usually come in small plastic bottles. There are generally 50 strips in a bottle.

Most test strips can help you measure multiple things within your spa water including pH, alkalinity, free chlorine, total hardness and various other metrics.

What are the best test strips for chlorine spa water?

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What are the best test strips for hydrogen peroxide / chlorine free spa water?

We recommend the Poppits 4 way test strips for testing your spa water if you are using a chlorine free / hydrogen peroxide sanitiser.

How do I use test strips in my spa?

Follow these simple steps to test your spa water using test strips and get the most accurate results;

1. Check the expiry date on your test strips

The first thing to check before using test strips is to ensure they haven’t passed their expiry date. Check for the expiry date on the bottle to make sure they are still current.

2. Check for moisture in the test strip container

Make sure that moisture hasn’t got into the test strip container. If water has got into the container, they will not work and you’ll need to get a new pack.

3. Make sure your water has warmed up to temperature

Your spa water will react differently at different temperatures. To get the most accurate results, ensure your spa is warmed up to operating temperature (usually between 32 degrees and 38 degrees celsius).

4. Turn off all jets and water features

It’s easier to test your spa water when it’s not moving around, so temporarily turn off the jets, waterfalls and other water features in your spa

5. Wash and dry your hands!

Wash your hands with clean water and then dry thoroughly. Then with completely dry hands, remove a test strip from the bottle. Washing your hands will help avoid anything from your hands affecting your measurements. Drying your hands carefully will prevent moisture from getting into your test strips bottle.

6. Dip your test strip into your spa water

Now for the fun part, dip your test strip into your spa water. Make sure you get the test strip at least 30cm below the surface of your water to get the most accurate results. Remove the strip sfter 5 seconds.

7. Remove the test strip and allow to dry

Pull the test strip out of the water and hold still for about 15 seconds to allow the colour to change to indicate the results of the test. Match the colours within 30 seconds of pulling the strip out of the water. Do not flick or shake dry as this can cause colours to mix, making it hard to read accurately.

8. Compare the result with the colour chart on the bottle

Once the colours on the test strip have changed, then hold them up against the colour chart on the back of the bottle to take the reading.

Please note, these instructions are guidelines only, you should refer to the test strip bottle for specific recommendations from the manufacturer.

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How do I read the pH level on my spa test strips?

In the image below, you can see a typical pH colour chart from the back of a test strip bottle.

If the pH reading is 6.2 or lower, the pH line on the test strip will turn a dark yellow. A pH around 6.8 will show light orange, pH level at the correct range around 7.2 to 7.6 will indicate a dark orange colour. If your pH is too high it will show red (7.8) or pink (around 8.4)

Read our detailed guide on understanding pH and alkalinity and adjusting your water balance.

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How do I read alkalinity on my spa test strips?

The total alkalinity colour chart below is similar to typical charts on many test strips bottles. The values are in parts per million (PPM). The ideal range for spa pools and swim spas is between 100 and 120ppm

If your total alkalinity is very low (up to 40), it will show an orange colour on your test strip. If it is between 40 and 80 it will display a brass/light green. Between 80 and 120 is close to the ideal range and this will show as an olive green or a light grass green.

If your alkalinity sits above the ideal range, the test strip will show a deep green or forest green.

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How do I adjust my spa water pH?

Once you’ve taken your readings from your spa water, you’ll need to decide if you need to adjust your spa water to balance it correctly.

If your water is not in the ideal range, start with Total alkalinity, then adjust your pH. Remember you should ensure your water is already warmed up so the chemicals will react correctly.

How do I Balance the Total Alkalinity in my spa water?

Total Alkalinity is the water’s ability to resist a change in pH. When your Total Alkalinity is balanced correctly it is more difficult for your water’s pH to go up or down - meaning your water pH will stay more consistent.

When the Total Alkalinity is not balanced, your pH can fluctuate much more readily. Meaning your water quality and clarity will be much more difficult to manage. This means you’ll spend more on maintaining your water with sanitiser and other products trying to get it clear

To adjust your total alkalinity up use an alkalinity increaser. Follow the instruction on the label for the correct amount depending on the volume of water in your spa. Start with adding a small amount, then turn your jets on to circulate your water and wait up to 30-60mins for the water to adjust.

Test your water again and add more increaser if you need to.

If you need to reduce the alkalinity use a pH decreaser and follow the same process. (Decreasing pH has the same effect as reducing alkalinity).

How do I adjust the pH levels in my spa water?

The pH level determines how acidic or basic the water in your spa is. If your pH is too low (under 7.2) then your water is too acidic. This means it is corrosive and it can begin to eat up the components in your spa like heater elements, jets and pillows and deteriorate the acrylic body of your spa. In addition, a low pH can cause skin irritation and inflammation.

You also don't want your pH to be too high - this means the water is too basic, the water can become cloudy, foamy, smelly and just generally unpleasant to look at and be in!

Having your water either too acidic or too basic means your sanitiser will have to work a lot harder to maintain the water quality, kill bacteria and keep your water clear.

Your test strip bottle will show you what the ideal range is, so check your test strip against the details on the back of the bottle. You’ll be able to see if you need to make any adjustments to your water pH from this result.

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Spa test strips frequently asked questions

How long do you leave a test strip in a spa? As a general rule, you should hold test strips underwater for about 5 seconds, then remove.

Are spa pool test strips reusable?

No, spa test strips are not reusable and should be discarded after use.

Why is my spa pH test strip yellow?

If your pH test reads a yellow or bright orange, this indicates your pH is much too low. You will need to add an alkalinity increaser product to get the levels into the ideal range around pH 7.2-7.6. This should show as a dark orange on the test strip.

Are there digital spa water testers available?

If you find the test strips difficult to use or read, you can also consider using a digital test meter to test your spa water. These digital meters are affordable and will pay for themselves quickly in comparison to purchasing bottles of test strips every few months.

We recommend the AQ digital pH tester which is easy to use and gives more accurate reading than test strips.

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Got more questions?

Talk to us on live chat using the chat button in the bottom right of the screen, or email us your spa chemical questions and we'll be happy to help!