Is Your Cyanuric Acid Low in Pool? | How to Raise it!

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Cyanuric acid aids in the prevention of chlorine dissipation caused by exposure to sunlight. If your cyanuric acid level is low (less than about 40ppm), you will need to use additional chlorine to maintain a proper chlorine level of 1.5 – 2.5ppm.

It will be significantly less expensive for you to increase your Cy level than to continue using more chlorine.

A concentration of CA of at least 30-35ppm is required to have an effect on chlorine.


Depending on how low it is, you can either add the required amount to bring your size pool up to that level per the dosage on the bottle, or if you use stabilized chlorine to maintain the pool and it is only 5-10ppm low, your cyanuric level will naturally rise as the CA in the tabs or granules dissolves.

Because CA can be reduced only by draining, backwashing, or splashing out, and because it always rises in a tab-maintained pool, I always approach from the low side.

A 4# bucket of CA works well in an 18,000 gal. pool. (And never backwash the filter until you are certain that all of the conditioner has dissolved!)

How to Increase Cyanuric Acid in a Swimming Pool

  • Calculate the volume of water in your pool
  • Determine the quantity of cyanuric acid (stabilizer) required.

Generally, you’ll need to add 1 pound of cyanuric acid per 10,000 gallons of water to raise the level by 10ppm.

Nota bene: Because the concentration of some cyanuric acids, also known as pool stabilizer, varies, check the instructions on the package before calculating the amount required.

A word of caution: it is far preferable to gradually increase the amount than to risk adding too much. Once cyanuric acid is in the pool, it can only be removed by draining some water.

  • Add in the Cyanuric Acid

You can pour liquid cyanuric acid directly into the filter box if you are using it.

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Cyanuric acid solution poured into filter box
If you’re using granular cyanuric acid (the most common type) or powdered cyanuric acid, the best way to begin is to place the cya in a skimmer sock.

Then, either suspend it in front of the return jet (using a pool pole) or insert it into the skimmer box.

Alternatively, you can combine cyanuric acid and warm water in a bucket and pour it into the skimmer box.

The disadvantage of pouring it directly into the skimmer box is that granules may end up on the bottom of your pool’s floor (which is unpleasant on your feet AND may damage pool liners).

Additionally, you will be unable to backwash your pool until the stabilizer has completely dissolved (about 2-5 days) – otherwise, you risk backwashing the cyanuric acid as well.

  • Set your pump to “circulate” or “filter.”

You only need to leave the liquid stabilizer on for a few hours to completely mix it.

Leave the pump running for 48 hours when using granular cyanuric acid. Then, for a week, run the pump for a minimum of four hours per day (you should be doing this anyway).

  • Conduct another water test and repeat if necessary.

If you use liquid cyanuric acid to increase the cyanuric acid levels, it will quickly dissolve in the water and raise the levels within a few hours.

It may take several days to a week for the granular form to dissolve completely. Therefore, do not panic and continue adding stabilizers if the levels do not immediately increase.

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Cyanuric Acid Low in Pool

Why is Cyanuric Acid Low?

In contrast to other chemicals in your pool, cyanuric acid does not naturally degrade. Once it’s in your pool, it’s permanently there, and the only way to remove it is to drain a portion of the water.

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So, you may ask, if it does not travel anywhere, why is the stabilizer set so low?

That is an excellent question! Cyanuric deficiency is caused by the process of removing and replenishing water.

The following are the most common reasons for water loss and the need to top off your pool:

  • Rain
  • Evaporation
  • Splashing
  • Leaking pool

It is not when the water is removed that the cyanuric acid levels decrease; it is when more water is added. Refilling the water has a dilution effect, which reduces the amount of cyanuric acid in your pool.

If you’ve encountered a high level of cyanuric acid in your pool, you might be interested in our article on How to Reduce Cyanuric Acid in Pools (Cyanuric Acid Too High)

Is Having Low Cyanuric Acid a Problem?

When the pool stabilizer level is low, chlorine is actually more effective at killing the bad bugs.

The issue with low cyanuric acid levels is that chlorine rapidly degrades in the presence of sunlight. Within a few hours of sun exposure, chlorine is rendered completely ineffective.

If your pool lacked cyanuric acid or the amount was insufficient, you’ll find that you’ll need to add significantly more chlorine to achieve effective sanitization.

Therefore, unless you enjoy spending more than necessary on chlorine and adding chlorine several times daily, I would recommend increasing chlorine stabilizer levels to the proper level.

Is it Safe to Swim in a Pool With Low Cyanuric Acid?

Swimming in a pool with low cyanuric acid levels is perfectly safe as long as the chlorine level is maintained.

How much chlorine should be added to cyanuric acid?

Free chlorine should be approximately 7.5 percent of the CYA level.

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That is, if your cyanuric acid level is 50ppm, you will require 3.75ppm (7.5%) of free chlorine to sanitize effectively.

Is Cyanuric Acid Required in All Pools?

No, not all pools require cyanuric acid. This is why.

As previously stated, sunlight rapidly degrades chlorine. The pool stabilizer (cyanuric acid) prevents this reaction from occurring. Thus, only pools exposed to UV light require cyanuric acid.

However, it is critical to note that this only applies to chlorinated pools. Pools that are sanitized using alternative methods such as ozone and ultraviolet light do not require cyanuric acid. Cyanuric acid exists solely to protect chlorine.

Which Products Contain Cyanuric Acid?

Another way to increase cyanuric acid levels is to use cyanuric acid-containing chlorine products.

These are commercially available as stabilized chlorine. Typically, pool shock products contain cyanuric acid as well.

These cyanuric acid-containing products include the following:

  • Dichlor
  • Trichlor
  • Chlorine Shock
  • Trichloroisocyanurate
  • Sodium Dichloroisocyanurate
  • Potassium Dichloroisocyanurate

These will increase the level of cyanuric acid, but at a slower rate than adding pure cyanuric acid.

These chlorine products are cyanuric acid-free:


In summary, swimming in a pool with low cyanuric acid levels is safe as long as the pool has an adequate supply of free chlorine.

To increase cyanuric acid levels in your pool, you’ll want to test the water and determine how much stabilizer you need to add.

Then determine the quantity of stabilizer to add (read the instructions on the stabilizer package). Stabilizer is best added in a skimmer sock, but it can also be mixed in a warm bucket of water and poured into the skimmer.

Cyanuric acid can take up to five days to dissolve, so be patient before adding more or you risk overdosing and developing cyanuric acid poisoning.

If you follow these steps, your pool’s chemistry will quickly be restored to normal levels.

Have Fun Swimming!

Author: Howard S. Baldwin

My name is Howard S. Baldwin. I am a work-at-home dad to three lovely girls, Jane + Hannah + Beauty. I have been blogging for the last 3 years. I worked for other Home and Lifetsyle blogs, did hundreds of product reviews and buyers’ guides. Prior to that, I was a staff accountant at a big accounting firm. Needless to say, researching and numbers are my passion. My goal is to be an informative source for any topic that relates to DIY life and homemaking.

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