Cyanuric acid—also called CYA, pool stabilizer, or pool conditioner—is a weak acid that protects your chlorine from the sun’s ultraviolet rays, allowing it to work for much longer periods without constant top-ups.
The ideal range for cyanuric acid in your pool is between 30 and 50 ppm (parts per million). Anything lower and you will likely see some undesirable side effects when it comes to your water chemistry.
Let’s talk about why this happens, why it matters, and how to raise cyanuric acid (CYA) in your swimming pool.
Why You Have Low Cyanuric Acid
The most likely reason is that you’ve only ever used unstabilized chlorine in your pool.
Heads up: Unstabilized chlorine, such as sodium hypochlorite (liquid chlorine), lithium hypochlorite, and calcium hypochlorite, is pure chlorine. Stabilized chlorine, such as sodium dichlor or trichlor, has added CYA to protect the chlorine.
When using unstabilized chlorine as your pool sanitizer, you need to add CYA to the water as well.
Unintended dilution of the pool water may also cause a drop in the pool’s CYA level. This can be due to water evaporation or a large splashout that requires refilling the pool, or even if it rains. Additionally, draining and refilling your pool will also result in low CYA levels.
Why Low Cyanuric Acid Is Bad News
Yes, cyanuric really is that important. Here’s what low CYA in the water will do to your pool water:
- Increased chlorine consumption. Chlorine is naturally destroyed by sunlight, and an entire pool’s worth can be decimated in a matter of hours. Low CYA levels won’t adequately protect it, which means you’ll be constantly feeding the pool more chlorine to keep it sanitized.
- Decreased chlorine effectiveness. With chlorine becoming less present in the pool due to sunlight consuming it, sanitation suffers. This allows pollutants, viruses, and bacterias in the water to take up space and even replicate.
- Green pool problems. A green pool is caused by a lack of clean water, which leads to algae growth. Depending on your situation, you can also develop pink slime or black algae, both of which leave your pool a nasty shade of ugh!
- Water chemistry imbalance. With low CYA not protecting chlorine, the chlorine level drops. This drop makes it inadequate for keeping the water clean, causing a chain reaction that affects other areas of the water chemistry such as the pool’s pH level and total alkalinity.
- Nasty pool smell. When free chlorine binds to ammonia pollutants such as sunblock, sweat, and urine in the water, it becomes combined chlorine (chloramines). Not only is this form of chlorine a much less effective sanitizer, it also kicks up a pungent “chlorine smell”.
How To Raise Cyanuric Acid In A Pool
Raising your CYA levels can only be done two ways.
Before dosing your pool, however, it’s imperative that you test the water, and balance both the pH level and total alkalinity level beforehand.
You can use test strips, a liquid test kit, or a digital test kit to find out where your pool’s chemical levels stand. CYA isn’t always a common testing parameter, so ensure the testing device you’re using will account for it.
Method #1: Use Stabilized Chlorine
Stabilized chlorine (sodium dichlor, trichlor) is available in either powdered granules, liquid, or puck/tablets. All are easy to add to the pool and can be done a few different ways.
Granules are mixed with water and poured into the pool, liquid chlorine (sodium hypochlorite) is also poured, and pucks can go either in your skimmer basket or a chlorine dispenser that floats in the pool.
There are also pool chlorinators which automatically feed the pool a set amount of chlorine, and you can use any kind of stabilized chlorine with them.
Here’s how to do it:
- Start by balancing and testing your pool water.
- Figure out how much chlorine you need to add to the pool so that it reaches between 1 ppm and 3 ppm.
- Safety is priority so always use chemically resistant rubber gloves and protective eyewear when handling chlorine. Long sleeves and pants are a good idea too.
- If using granules, add the measured amount of granules to a 5 gallon bucket of water and mix with a stir stick. Fully dissolve it so that no granules attach to the pool walls and damage the pool finish. Walk around the perimeter of the pool and pour the solution in.
- If using liquid chlorine, you can pour the measured amount straight into the pool or skimmer. Be careful it doesn’t splash on the walls. You may want to dilute it by adding it to a bucket of water first.
- If using pucks, add them to a chlorine dispenser or the skimmer basket. Be aware that some baskets can be damaged by the chlorine sitting in them for long periods of time.
- Retest the water after it has fully cycled (takes about 6 hours) to get an accurate reading of the chlorine and CYA in the pool. Adjust/add more if necessary.
Method #2: Use Pure Cyanuric Acid
Adding pure cyanuric acid is another option.
This method allows you to add it separately from chlorine, and will only need to be done once or twice a year at most.
Keep in mind that it is an acid, and can damage your pool if improperly added. Vinyl liner pools are especially susceptible and may need to be repaired, so follow the steps below for safe use.
Here’s how to do it:
- Test and balance your pool water so you will know where your CYA level stands and how much you need to raise it.
- Suit up in the proper protective equipment: eyewear, chemical-resistant gloves, and long sleeves with pants.
- Fill up a 5 gallon bucket with warm water.
- Measure the correct dosage of CYA for your pool by consulting the instructions on the product. In general, 13 ounces of CYA will raise a 10,000 gallon pool by 10 ppm.
- Add the CYA to the bucket of water (never the other way around!).
- Pour the solution directly into the pool’s skimmer.
- Allow time for the pool to fully cycle the water, distributing the CYA. Retest and repeat this process if more is needed.
How To Bring Cyanuric Acid Back Down
In cases where your CYA level is way above 50 ppm, you’ll need to take some steps to lower it so you don’t end up with a whole new set of pool problems.
There are 3 ways you can do this:
- Water dilution. This method requires you to drain the pool and refill it, and doing it slowly through multiple partial drains is recommended. While this will make the process take longer, it will protect your pool from potentially popping out of the ground – which will be very costly to resolve!
- CYA reducer. Products like Bio-Active are inexpensive, easy to add to the pool, and it’s safe to swim right after its application. The only drawback is you have to wait at least 1 week if you need multiple applications.
- Reverse osmosis system. RO is basically a specialized filter that purifies and recycles the pool water, so you’re not wasting it. An added benefit is that RO also reduces calcium hardness and total dissolved solids in the water. The downside is it’s a very expensive treatment option at $500 a pop.
Raising CYA: Simplified!
The problem of how to raise cyanuric acid in the pool is a very minor one. The addition of either stabilized chlorine, or pure cyanuric acid will both raise the CYA levels to where they need to be.
This will keep your chlorine well protected, eliminating problems with increased chlorine demand as well as decreased chlorine effectiveness.
