How To Lower Cyanuric Acid in a Pool

You bring down your cyanuric acid level by partially draining and refilling your pool. While there are other options like cyanuric acid reducers, they’re not very effective. But before you tackle a high CYA problem, you’ll need to stop making it worse.

Want the full routine for keeping your CYA in range? It’s all in The Pool Care Handbook.

• If your CYA is under 100 ppm: stop using stabilized chlorine and let rain and splash-out bring it down
• If your CYA is over 100 ppm: partial drain and refill
• If you have a vinyl liner pool: drain in rounds so the liner doesn’t shift or shrink
• If you have a fiberglass pool: avoid draining too low, especially with a high water table
• If you have a saltwater pool: you probably don’t have high CYA since your salt water generator (SWG) turns salt into unstabilized chlorine. That said, you will need to add a chlorine stabilizer manually and keep it higher (60 to 80 ppm)
• If you can’t drain: a mobile reverse osmosis service or a CYA reducer

Cyanuric acid (CYA), sometimes referred to as a pool conditioner or pool stabilizer, is crucial for maintaining your water’s chemical balance. But while CYA helps protect your chlorine from the sun’s ultraviolet rays, too much cyanuric acid isn’t good for your water chemistry.

Ideally, your cyanuric acid levels should be between 30 and 50 parts per million (PPM) and a bit higher if you have a saltwater pool. But if your levels are a lot higher, it may be time to lower the cyanuric acid in your pool.

How to Lower Cyanuric Acid (3 Ways)

Reducing cyanuric acid levels in your swimming pool isn’t an easy fix. But most importantly, stop adding more stabilized chlorine to your pool as soon as possible. This contains cyanuric acid, and continuing to add it to your water will make the problem worse.

1. Dilute Pool Water by Partially Draining and Refilling

Diluting your water is the easiest way to lower cyanuric acid in your pool. This means draining some of your pool water and replacing it with fresh water. Rainwater can also dilute your water and CYA levels, but the acidic nature of rain can upset your pool water’s balance.

Before diluting your water, test your water with test strips or a liquid test kit to determine your current CYA level.

First, completely turn off your filter system so it doesn’t kick back on with a timer. Begin partially draining your pool using a submersible pump. And as you drain your pool, just make sure your water levels never reach below the skimmer. This will protect your pump from running dry.

Once you’ve drained out some water, refill your pool with fresh water. Then, retest your pool chemistry.

Continue draining and refilling your water until you reduce cyanuric acid levels to the normal range between 30 and 50 ppm.

2. Try a Chemical Cyanuric Acid Reducer

Even though you can buy cyanuric acid reducers, they tend to be very expensive and don’t work for every pool owner. Remember, the most effective way to lower CYA is by draining and refilling with fresh water. But if you find that your CYA level is incredibly high and you can’t dilute your water, trying a CYA reducer may help.

Keep in mind that cyanuric acid reducers will not work if you’ve added clarifiers, algaecides, or phosphate treatments to the pool in the past week. You’ll also need your pool water to be at least 65°F. And your other pool chemicals, like pH and total alkalinity, should be in range before using.

3. Use a Reverse Osmosis Filter

If you can’t dilute your water and you have chronically high cyanuric acid levels, you may want to find a mobile reverse osmosis water service. Pool water passes through an incredibly fine semi-permeable membrane. Then the water moves through a tank and gets filtered by activated charcoal before going back into the pool.

However, reverse osmosis wastes a lot of water. You’ll usually create 1 gallon of wastewater for every 1 gallon that passes through your filter.

But many pool owners find reverse osmosis filters helpful because not only will they reduce CYA, but they will also lower calcium hardness and total dissolved solids.

What Causes High Cyanuric Acid?

The most common contributor to high CYA levels is stabilized chlorine. Stabilized chlorine comes with small amounts of CYA, which helps protect your sanitizer from being destroyed by the sun.

Most chlorine tablets or chlorine granules are made with stabilized dichlor and trichlor. So if you add one pound of trichlor chlorine to a 10,000-gallon pool, it can raise the CYA level by 6 ppm. On the other hand, calcium hypochlorite (cal-hypo), lithium hypochlorite, and liquid bleach are unstabilized. These won’t increase your CYA levels.

As you add stabilized chlorine to your water, the levels of cyanuric acid can build up over time, even as the chlorine levels fluctuate up and down. That’s because as water evaporates from the swimming pool, cyanuric acid remains in the water. So while you’re trying to bring down your cyanuric acid levels, stop adding stabilized chlorine.

Not everyone needs to worry about high CYA levels, though. If you’re a pool owner who drains and refills your pool each year or you have an indoor pool, you likely won’t need to worry about a build-up of cyanuric acid. But if you have an outdoor pool you keep open all year and you don’t get a lot of rain, you’ll need to monitor your CYA levels.

Keep Your CYA From Creeping Back Up

High CYA always comes from adding unstabilized chlorine without keeping an eye on your levels. The fix is knowing which chlorine to use, how often to test, and what your levels should look like week to week.

That’s exactly what The Pool Care Handbook gives you. A simple weekly routine, the right range for every chemical, and step-by-step fixes when something goes wrong. It works for chlorine and saltwater pools, and you’ll never have to guess what your pool needs again.

And our if you enter your test results into our Pool Care App every week, it’ll warn you when you have CYA creep. That way, you can avoid ever dealing with high CYA again.

Frequently Asked Questions

Need more help lowering the CYA levels in your pool? Here are some common questions and answers.

How do I lower the cyanuric acid in my pool without draining it?

You can try using an expensive CYA reducer or a mobile reverse osmosis service. Or partially draining the water by a few inches and adding fresh water to your pool afterward.

Is it safe to swim in a pool with high cyanuric acid?

While technically it is safe to swim in a pool with high levels of CYA, it can affect your other chemicals. Too much cyanuric acid can reduce your chlorine effectiveness, making the water unsanitary.

What if my cyanuric acid is too high?

High cyanuric acid levels reduce your chlorine’s ability to sanitize. And you may experience cloudy water and algae issues. When CYA increases, the amount of available chlorine that can sanitize the water decreases. Your free chlorine levels should be 7.5% of your cyanuric acid levels. So if your pool has a CYA level at 40 ppm, you’ll need to keep your free chlorine levels at 3 ppm to effectively sanitize your water.