What Is Pool Stabilizer?

Written by Michael Dean
June 12, 2024

bag of pool stabilizer next to a swimming pool

If you chlorinate your pool and don’t add pool stabilizer, it will take approximately 2 hours for most of the chlorine to evaporate out of your swimming pool. Adding new chlorine every two hours is neither practical nor cost-effective, so you’ll definitely want to add pool stabilizer into the mix.

Below, I go into what pool stabilizer is, different types of pool stabilizers, how much you should use in your pool or hot tub, when to use it, and how to safely add it to your swimming pool.

Main Takeaways

  • Pool stabilizer is made from cyanuric acid, which helps protect chlorine from the sun’s UV rays.
  • If you have an outdoor pool or spa, you need pool stabilizer.
  • You can add pool stabilizer in two ways: 1) Add a stabilized chlorine (dichlor or trichlor), or 2) add a liquid or granular cyanuric acid additive.
  • You should keep the CYA levels around 30-50 ppm for chlorine pools, 60-80 ppm for saltwater pools, and 30 ppm for hot tubs.

What Is Pool Stabilizer, and What Does It Do?

Using a pool stabilizer is a necessary part of keeping your pool clean. Pool stabilizer is made from cyanuric acid (CYA). CYA slows down how quickly chlorine evaporates so that chlorine will stay in the water longer.

CYA works by binding to chlorite ions in chlorine and protecting them from UV ray damage. Without a stabilizer, UV rays can easily break apart the chlorite ions in chlorine, which allows them to evaporate into the air.

Pool stabilizer comes in several forms:

  • Granules
  • Liquid
  • Combined stabilized chlorine tablets or sticks (trichlor)
  • Combined stabilized shock (dichlor)

It can be a little confusing when you’re researching what to get because pool stabilizer is also called pool conditioner, chlorine pool stabilizer, and chlorine stabilizer.

Here’s a photo from my recent trip to Leslie’s pool supply store, where they market their stabilizer product as conditioner.

Pool Mate Swimming Pool Stabilizer and Conditioner

Stabilizer is just a fancy name for cyanuric acid. Pool Mate makes a good product that is affordable.

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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Do You Need to Use a Stabilizer in Your Pool?

If you have an outdoor pool or hot tub or an indoor pool or hot tub in a room with windows, it’s essential to use a stabilizer. The only time you would not need a stabilizer in your pool or hot tub is if it’s indoors in a room with no windows like some hotels have.

When CYA forms an ionic bond with chlorine, it takes longer for chlorine to reach its full Oxidation Reduction Potential (ORP) and start sanitizing the water. However, without the ionic bond, the chlorine will evaporate in the sunlight.

If you treat your outdoor pool with chlorine and do not use a stabilizer, you’re throwing your money away. It only takes two hours for the sun’s UV rays to consume 95% of your pool’s unstabilized chlorine in the shallow end and 75% of unstabilized chlorine in areas deeper than four and a half feet.

Of course, how fast you lose chlorine depends on other factors like water temperature and PH level. But the bottom line is that if you do not add a stabilizer to your pool with your chlorine, your chlorine won’t last very long at all.

Types of Pool Stabilizer Explained

There are two ways to add a pool stabilizer to your pool. The first way to add a stabilizer to your pool is with a stabilized tablet, stick, or shock that contains both chlorine and CYA. The second way to add a stabilizer to your pool is as a liquid or granular additive separate from your chlorine additive.

Stabilized Chlorine Tablets or Sticks (Trichlor) or Shock (Dichlor)

The main difference between tablets or sticks (trichlor) and shock (dichlor) is chemical strength and how to use the product.

Tablets and sticks are for everyday pool use while shock products have high chlorine levels that “shock” a pool to remove chloramines, waste, and bacteria after a contamination event or to remove visible algae.

Stabilized chlorine is the easiest way to add chlorine and stabilizer to your pool at the same time without a second step. Both trichlor and dichlor contain over 50% CYA by weight. You’ll likely never have to adjust chlorine levels when you add them as a combination duo.

I suggest first-time pool owners use stabilized chlorine tablets or shock because it’s easier and requires less extra work. However, I still recommend regular testing to make sure the CYA levels stay within the proper range.

Liquid and Granules

If you’re a pool owner that likes to be in complete control over the exact amount of CYA stabilizer in your pool, you might decide to go the route of liquid or granules for adding stabilizer.

Some people choose pool stabilizer liquid over granules because they don’t feel like the granules dissolve well enough. I’ve never had this problem, but I also make sure to use granules as close to 100% cyanuric acid as possible. If the CYA isn’t concentrated enough, your CYA levels won’t rise as much, either.

If you can’t decide, head to my full breakdown of liquid vs. granules.

How Much Chlorine Pool Stabilizer Should You Use?

If you don’t add enough pool stabilizer to your pool, your chlorine will start to evaporate, so it’s important to keep levels in check.

Keep in mind that if you decide to add stabilized chlorine tablets or shock, you’re automatically adding a stabilizer every time you’re treating your pool with chlorine. Following the proper chlorine level guidelines for your pool should result in adding the correct amount of CYA. You can use my pool stabilizer calculator to figure out exactly how much CYA to add.

Chlorine Pools

In a chlorine pool, the ideal amount of stabilizer is between 30 ppm and 50 ppm. Below 30 is ineffective, and above 50 interferes with chlorine’s ability to kill bacteria and prevent algae. Too much can also damage your vinyl liner if you have one. You’ll generally want about 7.5% chlorine in the pool as stabilizer.

Saltwater Pools

If you own a saltwater pool, you should keep CYA levels between 60 and 80 ppm. Higher CYA levels are necessary for saltwater pools because sunlight doubles chlorine evaporation in saltwater pools during photolysis.

Hot Tubs

Hot tubs require a higher concentration of chlorine than pools. You should keep CYA levels as low as possible in a hot tub—around 30 ppm.

Most hot tub owners add a separate stabilizer (like dichlor or trichlor) instead of stabilized chlorine to a hot tub. Adding enough pool-specific stabilized chlorine for the amount of chlorine needed in a hot tub also adds in extra CYA. With a high level of CYA, the chlorine will become ineffective for sanitization.

If you prefer using stabilized chlorine, be sure to get a spa-specific type that considers the right balance of chlorine to CYA for a hot tub.

Cryptosporidium Contamination

Cryptosporidium (“crypto”) parasites sometimes infect a pool with fecal contamination. If you need to hyper-chlorinate your pool because of a Cryptosporidium outbreak, lowering CYA levels to 15 ppm before chlorinating is necessary.

When to Use Pool Stabilizer and When Not to Use It

Even if you decide to go with stabilized chlorine, you should check CYA levels regularly to determine if it’s in the correct range and whether or not to add pool stabilizer.

When to Check Stabilizer Levels

Checking pool stabilizer levels is vital if you use a separate stabilizer rather than stabilized chlorine. A quality pool-chemistry testing strip will test for CYA levels.

The first time you will want to check the CYA level in your pool is three to five days after your pool filter has been circulating water for the season. It’s useless to check it sooner than that because it’s denser than water and settles to the bottom of the pool without circulation.

If you keep your pool running year-round, you’ll want to check CYA levels regularly.

When Do You Need to Add Pool Stabilizer?

If you’ve tested the pool water and determined that it has less than the minimum CYA levels for your type of pool or hot tub, you will need to add more pool stabilizer.

Luckily, CYA doesn’t evaporate like other pool additives, so it’s not likely to decrease unless it’s diluted by adding extra water to the pool or from rainfall.

When Should You Not Add Pool Stabilizer?

You already know there’s no reason to add stabilizer to an indoor pool or hot tub with no UV exposure.

Otherwise, if CYA levels are within the correct range for your pool type or hot tub, you do not need to add more stabilizer.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

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How to Safely Add Pool Stabilizer

Safe handling of pool chemicals is essential for your safety. Once you’ve determined that you need more pool stabilizer, these are the steps you should follow:

  1. Calculate how much stabilizer you should add. To achieve 30 ppm, you need one pound CYA per 4000 gallons of water.
  2. Put on gloves and goggles. CYA is a strong acid, and you don’t want any on your skin or in your eyes.
  3. Mix the CYA with warm water. It’s best to mix it in a five-gallon bucket.
  4. Add the mixture to the pool. Follow package directions about putting it into the filter or directly into the pool.

Adding Too Much Stabilizer

If you add pool stabilizer beyond the maximum suggested range, the CYA will prevent the chlorine from doing its job. Having too much stabilizer causes a problem called “creep.” CYA levels will creep up too high over time, and your chlorine will no longer be able to disinfect your pool.

Topping off the pool with more water is an easy way to get CYA levels back under control.

Final Thoughts

If your pool or hot tub is exposed to sunlight, you must think about what type of pool stabilizer you will need. But adding isn’t a big deal since you can buy stabilized chlorine tablets or shock, and it doesn’t often need adding as a stand-alone additive.

Add it, forget it, and enjoy the water. If you need more tips, head to my guides on swimming pool chemistry, the correct order to add pool chemicals, and how to take care of a pool.

Questions? Drop me a line.

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