decrease cyanuric acid in hot tub

How To Decrease Cyanuric Acid In Hot Tub?

Walking into a warm and bubbly hot tub can be one of life’s great pleasures. But is it possible to keep it that way for a long time? For that, you’ll need to know a bit about water chemistry. 

One compound that hot tub owners might be familiar with is Cyanuric Acid (CYA). Generally, CYA helps protect sanitizers such as chlorine from the damaging effects of sunlight in pools and hot tubs. However, keeping the level right can be a challenge.

Negative Effects of High Cyanuric Acid Levels

Cyanuric acid is known as a conditioner or a stabilizer. The compound is both blessing and a curse for hot tub maintenance. While it protects chlorine from the UV rays of the sun, too much of it can cause problems.

According to Aqua Magazine, high levels of CYA can result in early draining and refilling of your hot tub. When the CYA level exceeds 70 parts per million, the effectiveness of chlorine in your hot tub decreases. 

The CYA forms temporary bonds with free chlorine, negatively affecting chlorine levels. As a result, As a result, chlorine becomes less effective at disinfecting. The amount of time chlorine takes to kill bacteria lengthens as well. 

In addition, during summer, you will find chlorine dissolves in the tub, while cyanuric acid will remain there as waste products.

It is, thus, crucial to manage the levels of cyanuric acid in your hot tub. But how do you do that?  

Stay tuned as we look into the possible methods to control and decrease cyanuric acid levels in hot tubs effectively.

decrease cyanuric acid in hot tub

Water Dilution

Water dilution is one of the most simple and cost-effective solutions for managing the high level of cyanuric acid (CYA) in your hot tub. 

Diluting Hot Tub Water with Fresh Water

The water dilution method involves partially draining the existing water and refilling it with fresh ones. When you replace part of the high CYA water with fresh water, you automatically bring the level down. The method is also effective in lowering other chemicals.  

Calculating the Amount of Water to Replace

Before you replace water, you need to know how much you need to drain and replenish. You should decide the amount based on the current level of CYA in your hot tub. 

If the CYA level is extremely high, you may need more water. As a rule of thumb, if you find your CYA level to be twice what it should be (over 100 ppm), you should replace half the water at least.

Step-by-Step Guide to Partial Draining and Refilling

Turn off the hot tub: 

You must turn off the hot tub before you start the draining and refilling process. It is to avoid electrical hazards. 

Drain a portion of the water: 

Now, drain about one-third to half of the tub water. It will remove a significant amount of cyanuric acid from the water.

Refill with fresh water:

Now, refill the hot tub with fresh water using a hose. Make sure to fill up to the recommended level. 

Balance the hot tub water:

Finally, check the chemical levels. If it is not at the right level, make sure to adjust it properly. This ensures a perfect balance of chemicals in the hot tub water.

After the replenishment, some cyanuric acid will still remain on the tub wall, plumbing and filtration areas. So expect to have a moderate level of cyanuric acid.

Test the CYA level. If it is between 30 and 50 ppm, it is fine.

Precautions and Considerations for Draining and Refilling

  • Before draining your hot tub check the local rules of your locality, as some areas may restrict draining hot tubs. 
  • Since draining the tub may affect the hot tub warranty, make sure to consult your manufacturer or dealer first. 
  • Disconnect the hot tub from any power supply before the draining process. This helps avoid electrical issues.
  • When you are refilling the water, you must use treated water. Untreated water may introduce new contaminants such as metals, bacteria, or others.

Cyanuric Acid Reducers

One of the effective ways to lower the CYA level is using a cyanuric acid reducer. You do not need to worry about draining a lot of water with this product. 

What are the Chemical Products for Lowering Cyanuric Acid?

A lot of suppliers offer products to reduce cyanuric levels. All of them contain common compounds such as enzymes and other additives. They help break down the excess CYA present in water. Plus, the products are affordable and easy to use.

Some benefits of Cyanuric Acid,

  • You do not need to opt for draining the hot tub water
  • It will prevent chlorine lock, which is caused by high CYA

However, you should only use this approach if the first method we discussed is not possible or not working. It is because the CYA reducer may disturb the balance of overall chemicals in the hot tub.

Bio-Active 100-Percent Cyanuric Acid Reducer Powder

Usage and Effectiveness of Cyanuric Acid Reducers

As we mentioned earlier, there are different brands that offer CYA reducers. However, the performance of the product depends on the type and the brand. So you need to be careful when purchasing one. Make sure to read the labels as well as the instructions given.

If you can successfully pick a product, you simply need to sprinkle the right amount and wait for the magic to happen. It will work automatically on the excess CYA by converting them into gases. This then evaporates into the air, reducing the level in the hot tub.

Keep in mind that the product works slowly. So you need to wait for days or even a couple of weeks. Also, when you are using CYA reducers, do not use stabilized chlorine.

Finally, for a healthy and balanced hot tub environment, be sure to monitor and maintain the CYA levels regularly.

Maintenance and Prevention

It is always better to prevent problems than to fix them when it comes to hot tub maintenance. This calls for proactive approaches that help keep cyanuric acid at an optimum level. The following section discusses how to prevent excessive buildup of CYA in your hot tub.

Tips to Prevent Excessive Cyanuric Acid Build-up

  • Monitor the CYA level regularly. Using a test kit, you should carry out tests at least once a month. However, if you are using dichlor or trichlor, run this test once per week.
  • The CYA level must be below 100 ppm. A level of 30-50 ppm is ideal.
  • If you use cyanuric acid in your hot tub, make sure to maintain a residual chlorine level of 2.0 ppm.
  • Cyanuric acid is best suited for outdoor pools. It is advised not to use it in hot tubs, spas and indoor swimming pools.
  • If you are already using dichlor or trichlor, it is not necessary to put additional cyanuric acid into the hot tub.
  • Make sure you monitor and manage the CYA level strongly. Otherwise, expect excessive buildup of the chemical.


It is crucial to maintain the right levels of cyanuric acid level in your hot tub. If not, you will have to deal with the effectiveness of chlorine, slow cleaning, unusual organism buildup, and overall safety of the environment.

It is thus recommended to check the CYA level regularly and keep it at the standard level. You may either replace the hot tub water or use chemicals. Both are effective, but the second one comes with some downsides.


Hi, I'm Shimul, the founder of Pooltub Life. I'm excited about sharing the latest outdoor living trends with you. My goal is to provide you with up-to-date information that will help make your POOL & HOT TUB stylish and enjoyable. Read About Me More । Follow on Facebook

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