Cyanuric Acid: A Hot Topic in Hot Tub Care

cyanuric acid hot tub

If you’re a hot tub enthusiast, you’ve likely come across the term “cyanuric acid.” This chemical, often abbreviated as CYA, is a common additive in hot tub water, but it’s not without its controversies. While CYA can help to protect chlorine from the sun’s ultraviolet (UV) rays, it can also build up over time, making it more difficult for chlorine to effectively sanitize the water.

In this blog post, I’ll delve into the world of cyanuric acid and hot tubs, exploring its benefits, drawbacks, and ideal levels. We’ll also provide tips on how to properly manage CYA levels in your hot tub to ensure safe and enjoyable soaking experiences.

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What is Cyanuric Acid?

Cyanuric acid, also known as CYA, is a chemical compound commonly used to stabilize chlorine in swimming pools and hot tubs. It acts as a sunscreen for chlorine, protecting it from degradation caused by ultraviolet (UV) rays from the sun. By shielding chlorine from UV rays, cyanuric acid helps to maintain its effectiveness in sanitizing the water, preventing the growth of bacteria and algae.

Cyanuric acid is typically added to pool or hot tub water in the form of a stabilizer product. The recommended level of cyanuric acid in a hot tub is between 30 and 50 ppm (parts per million). If the CYA level is too low, chlorine will degrade quickly, requiring more frequent additions to maintain proper sanitation. Conversely, if the CYA level is too high, chlorine will become less effective at sanitizing the water, potentially leading to the growth of microorganisms and health risks.

While cyanuric acid can be beneficial in stabilizing chlorine, it’s important to note that it doesn’t actually sanitize the water itself. It simply helps to prolong the effectiveness of chlorine, which is the primary sanitizer in most pools and hot tubs. Additionally, cyanuric acid can accumulate over time, making it more difficult to maintain proper chlorine levels.

Here’s a summary of the pros and cons of using cyanuric acid in hot tubs:


  • Stabilizes chlorine, protecting it from UV degradation
  • Helps to maintain chlorine effectiveness over time
  • Reduces the frequency of chlorine additions


  • Doesn’t sanitize the water itself
  • Can accumulate over time, making chlorine less effective
  • Can make it more difficult to maintain proper chlorine levels

Overall, cyanuric acid can be a useful tool for hot tub owners, but it’s important to use it judiciously and monitor its levels regularly.

How is Cyanuric Acid Produced in a hot tub?

yanuric acid, also known as CYA, is not naturally produced in hot tubs. Instead, it is typically added externally by the hot tub owner or a professional. The most common way to add CYA to a hot tub is through the use of a stabilizer product, such as dichlor or trichlor chlorine. These chlorine types already contain a certain amount of CYA, which is released into the water when the chlorine is dissolved.

In rare cases, CYA may enter a hot tub through other means, such as:

  • Water sources: If your hot tub’s water supply contains CYA, it could be introduced to the tub when you refill it. This is more common in areas with municipally treated water that uses CYA as a disinfectant.

  • Corrosion products: If your hot tub has metal components that are corroding, they could release CYA into the water. This is usually a sign of a more serious problem with the tub’s plumbing or metal parts.

However, the primary source of CYA in hot tubs is the intentional addition of stabilizer products. It’s important to monitor CYA levels regularly and adjust as needed to maintain the recommended range of 30-50 ppm. Excessive CYA can interfere with chlorine’s ability to saniti

Is Cynanuric Acid in my hot tub Dangerous?

yanuric acid (CYA) is not inherently dangerous when present at recommended levels in a hot tub. In fact, it serves a valuable purpose by stabilizing chlorine and protecting it from degradation by ultraviolet (UV) rays. This helps to ensure that chlorine remains effective in sanitizing the water and preventing the growth of bacteria and algae.

However, problems can arise when CYA levels become too high. Elevated CYA levels can make it more difficult for chlorine to do its job effectively, increasing the risk of contamination and potential health hazards. Additionally, high CYA levels can contribute to scaling and corrosion of hot tub components.

The Centers for Disease Control and Prevention (CDC) recommends not using CYA in hot tubs due to the potential for these issues. They suggest using alternative sanitizing methods, such as non-chlorine sanitizers or a combination of non-chlorine and low levels of chlorine, to avoid the complications associated with high CYA levels.

If you choose to use CYA in your hot tub, it’s crucial to maintain its concentration within the recommended range of 30-50 ppm. Regularly test your hot tub water to monitor CYA levels and adjust them accordingly. If CYA levels become too high, consider partially draining the hot tub and refilling it with fresh water to lower the CYA concentration.

Remember, proper hot tub maintenance is essential for ensuring safe and enjoyable soaking experiences. Regularly monitor your hot tub’s chemical levels, including CYA, to maintain proper sanitation and prevent potential health risks.

How do I get rid of Cynauric Acid in my Hot Tub?

The only effective way to remove cyanuric acid (CYA) from your hot tub is to partially drain and refill it with fresh water. CYA is a stabilizer that binds to chlorine and prevents it from being broken down by sunlight, but it also accumulates in the water over time. This can make it difficult for chlorine to effectively sanitize the water, and it can also lead to other problems such as scaling and corrosion.

Here are the steps on how to get rid of CYA in your hot tub:

  1. Test your CYA level. You can use a pool or spa test kit to measure the CYA level in your hot tub water. The recommended range for CYA is 30-50 ppm.

  2. Determine how much water to drain. The amount of water you need to drain will depend on your current CYA level and your desired CYA level. You can use a pool calculator to help you figure out how much water to drain.

  3. Drain the water. Slowly drain the water from your hot tub until you have reached the desired level.

  4. Refill the hot tub with fresh water. Use fresh water from a hose or a bucket.

  5. Rebalance the chemicals. Once the hot tub is refilled, you will need to rebalance the chemicals. This includes adding chlorine, pH stabilizer, and alkalinity increaser or decreaser.

  6. Test the water. Test the water again to make sure that the chemical levels are balanced.

Here are some additional tips for removing CYA from your hot tub:

  • Drain the water slowly. This will help to prevent damage to your hot tub.

  • Use a pool vacuum to remove any sediment from the bottom of the hot tub. This will help to ensure that the fresh water is able to circulate properly.

  • Run the hot tub jets for several hours after refilling it. This will help to circulate the fresh water and chemicals.

  • Monitor the chemical levels closely. It may take several days for the chemicals to balance properly.

Removing CYA from your hot tub is a relatively simple process, but it is important to follow the steps carefully to avoid any problems. If you are not comfortable doing it yourself, you can always hire a pool and spa professional to help you.

Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

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