High CYA in hot tub? Here’s how to fix it

clean hot tub

Alkalinity, pH, phosphates, chlorine, oxidizer. When you are a new hot tub owner, becoming familiar with hot tub chemistry can feel a bit like cramming for a high school exam. But for some, there’s one acronym that doesn’t seem to come up in your prep materials: CYA.

So what is CYA?

CYA stands for cyanuric acid. A stabilizer or conditioner, CYA is a chemical that protects chlorine from breaking down in sunlight and combines with chlorine to significantly lower the active chlorine concentration. 

For pool owners, CYA and how it works in water is important. The sun’s rays can destroy chlorine in less than 20 minutes. With CYA, chlorine lasts much longer and can effectively keep water clean and clear. For owners, that means that they do not have to add chlorine every day. Instead, they add it a couple times a week. 

But for hot tub owners, high levels of CYA can be problematic.

high cya hot tub
Chlorine is critical for keeping your hot tub water clear and clean. But many products are stabilized with CYA.

How CYA works

One of the most important things you have to do as a hot tub owner is keep your chemicals balanced. You should regularly check your water using test strips or a chemical kit and add product, as necessary, to balance your levels.

But when it comes to CYA, you might not know you are adding it to your spa. And it’s not a product that you will likely see on the shelf at your local spa retailer.

Cyanuric acid comes in either a liquid form or as a granule. However, it’s likely added to a pool or spa sanitizer. Pool owners use trichlor tablets while hot tub owners should use dichlor granules.

Note: You should follow the recommendations of your manufacturer and use the sanitizer that works best for your filtration system.

Cyanuric acid works by attaching to the free chlorine in your water. When chlorine and CYA bond, the chlorine is protected from the sun’s UV rays. However, chlorine is still able to do its job — killing bacteria and other contaminants in the water. 

CYA, though, will cause chlorine to work more slowly, especially in a hot tub. The water is not only kept at a higher temperature but spas are more likely to be kept covered.

high cya hot tub
Too much CYA in your hot tub water can render your chlorine ineffective.

The problem with high CYA in hot tubs

Most backyard hot tubs use chlorine. And it’s not just that you add it to the water a couple times a week. When the chlorine is working, there is a chemical reaction. The byproduct of that reaction is chloramines. The chlorine you added is no longer available to kill other organics.

Most chlorine, whether it’s for a pool or hot tub, is stabilized with cyanuric acid. However, the CYA can build up. The more CYA, the less effective your chlorine will become. And, as you know, you need chlorine to kill bacteria, algae, and other things you don’t want in your water.

Hot tub owners might not notice a build-up of cyanuric acid and some chemical kits might not even test for it. However, you might notice that your water is cloudy or has an odor. Keep in mind that well-maintained water will either have a fresh aroma or none at all.

In addition, research shows that high levels of CYA can do more than affect the quality of your water. It can damage the components of your spa and cause skin irritation.

Problems can begin when your cyanuric acid levels are above 50 parts per million. And if your water is over 90 degrees, which most hot tubs are, the readings might not be accurate. In fact, it might test 15 ppm lower than what it is.

More than that, if your CYA levels are high, you can get inaccurate results for alkalinity and pH levels.

clear hot tub water
Using an oxidizer in your spa can help lower your CYA levels.

Preventing high CYA in hot tubs

Just add chlorine. When frustrated hot tub owners are struggling with water issues, many are told to just add more chlorine. However, if you are struggling with high levels of cya, adding more chlorine will not help.

In fact, it might make it worse.

Since most hot tub sanitizers are stabilized with cyanuric acid, you are adding even more CYA to your water when you add chlorine. The only shock will be that your water is worse.

But what are you supposed to do if you need to add chlorine but need to avoid cyanuric acid? 

Using an oxidizing shock product can help. Oxidizers break down chloramines and organic matter, allowing your chlorine to work more effectively. Many manufacturers recommend that you use hot tub shock once a week as part of your water care routine. 

Another way to prevent high CYA in your hot tub is to use a sanitizer that does not use it as a stabilizer. The Frog @ease system is a floating system that slowly releases chlorine into your hot tub water. The product does not contain cyanuric acid, which means you don’t have to worry about build-up.

hot tub chemical rules
Regularly ch

Still struggling with CYA?

Many hot tub levels can be balanced with the right product. If your pH is low, you can add a pH increaser. You can add a booster if your calcium hardness levels are low.

But when you are struggling with CYA levels? There’s not a hot tub chemical that you can add.

The best solution if an oxidizer has not helped is to partially drain your hot tub and add fresh water. To carry out a partial drain, turn off your hot tub at the breaker. Some hot tubs might have internal drains but you can use a garden hose to lower the water levels. 

While the hot tub is turned off, rinse and clean your filters thoroughly. Your filters have a significant impact on the quality of your water. Not only will it remove any dirt and debris but any total dissolved solids as well.

Hot tub help when you need it

Whether you need help managing water care or want backyard ideas, our forum and its members offer tips and tricks.