As a pool owner, you know the struggle of buying and adding chemicals to your pool. Sometimes you might think your pool is a black hole, devouring everything you put in and leaving no trace. In reality, the sun is the culprit, eating up your chlorine almost as fast as you add it.

The good news is there is a solution — at least for your chlorine. If you’re sick and tired of fighting against the onslaught of UV rays from the sun and its constant destruction of your sanitizer, you’ve come to the right place. Today we’re going to introduce you to your new best friend: pool stabilizer. 

What is Pool Stabilizer?

Pool stabilizer goes by several names: pool conditioner, chlorine stabilizer, or cyanuric acid. You can get it in granule or liquid form to add to your pool water. 

When cyanuric acid is mixed with chlorine it is known as stabilized chlorine. You might see it called trichlor when it’s mixed with chlorine tablets or sticks and dichlor when it’s mixed with pool shock.

The main purpose of pool stabilizer is to keep the chlorine in your pool water from degenerating due to UV exposure. Sunlight triggers a chemical reaction with chlorine, causing it to breakdown more quickly than it normally would. This is bad news for your wallet: the faster your chlorine breaks down, the more chlorine you need to buy to keep your pool water chemistry balanced.

How Pool Stabilizer Works

From the moment you add chlorine to your pool, the sun’s powerful radiation goes to work, burning off your chlorine — sometimes as fast as you put it in. No, I’m not being melodramatic here:  the sun can actually eat up to 1 ppm (part per million) of chlorine every hour if it’s not protected.

When you bolster the chlorine in your pool with a silent helper like pool stabilizer, what it’s actually doing on a molecular level is quickly binding to the chlorite ions in chlorine. These guys are stronger together than apart: without this chemical bond, the UV radiation would break apart the chlorine, causing it to lose all sanitizing power.

The Upside of Pool Stabilizer

Pool stabilizer has one job and it does it well. Its job is to keep the chlorine in your pool longer than it would be without help. In fact, in the presence of pool stabilizer, chlorine can last 3 to 5 times longer than without it.

It should be no surprise that increasing the lifespan of chlorine is a major benefit. That stuff is not cheap and your pool needs it all the time. If you don’t use stabilizer or let your levels drop too low, you’re opening up a Pandora’s box of possible bacteria and algae growth that can take over your pool and destroy your water chemistry in a matter of hours.

By adding stabilizer to your pool, you’re effectively giving the chlorine a fighting chance against the sun. Think of it as a suit of armor; it still has to go into battle and will certainly get banged up, but it will last a lot longer than it would without it.

The Downside of Pool Stabilizer

This all sounds great, right? So, of course, there has to be a catch. Although pool stabilizer can provide some amazing benefits in protecting your chlorine and extending its lifespan, the downside is that the effectiveness (or cleaning power) of the chlorine is decreased.

When pool stabilizer bonds with chlorine, the chlorine’s ability to kill bacteria (and therefore sanitize) is somewhat limited. The term for chlorine’s sanitizing power is known as the Oxidation Reduction Potential. This potential is reduced when chlorine and pool stabilizer bond together. To put it simply, stabilized chlorine lives longer but is less powerful than it would be in its original state.

You also need to keep an eye on the stabilizer levels in your pool, just as you do with the other chemicals floating around in there. If the amount of stabilizer in your pool water gets too high, there’s the possibility of getting chlorine lock when the chlorine is actually overwhelmed by the stabilizer. 

Chlorine lock is bad news because it completely throws off your water testing, giving a negative result for chlorine levels, even if it’s present in the pool. 

How Much Pool Stabilizer Do You Need?

According to the Pool & Hot Tub Alliance, the ideal range for pool (or chlorine) stabilizer should be between 30 and 50 ppm (parts per million) when used in the average backyard pool. The concentration should never exceed 100 ppm, which is the absolute upper limit prescribed by the World Health Organization

Maintaining levels around 50 ppm will safeguard your chlorine, allowing it to do its job without getting destroyed by sunlight. Remember, more pool stabilizer doesn’t mean more protection, it will actually just decrease your chlorine’s efficacy. This is a Goldilocks situation — 50 ppm is “just right” and stabilizer is really only helpful at these specific levels.

Pro Tip for Indoor Pools: Pool stabilizer is not recommended for indoor pools that do not receive direct sunlight. Since indoor pools don’t have to deal with the destructive effects of UV radiation (i.e. they don’t need to be ‘stabilized’ from anything), the pool stabilizer would actually counteract your chlorine’s effectiveness, rather than doing any good.

The Exception to the Rule

One huge caveat to the 50 ppm rule when using pool stabilizer is if you find yourself with a cryptosporidium outbreak in your pool. If you’ve never heard of it or had to deal with it — congratulations! You’ve never had fecal matter infected by parasites in your pool.

Crypto is a nasty parasite that can be introduced to pool water through fecal contamination (among other ways) and is nearly impervious to chlorine. The only way to get rid of it is to hyperchlorinate your pool, I mean, like really blast it with the stuff.

However, in order for the massive dose of chlorine to actually work, you’ll need to lower your pool stabilizer levels to 15 ppm. This is the only way to get rid of this dangerous parasite invasion and probably the only time you’ll need to lower your stabilizer levels so drastically. 

Also, remember to replace your pool filter and balance the water once you’ve eradicated the crypto from your pool before letting any swimmers back in.

The Best Time to Use Pool Stabilizer

You will probably only need to add pool stabilizer to your pool water once a year. No, that is not a misprint. 

Once. A. Year. Amazing right? 

Pool stabilizer not only stabilizes the chlorine in your pool but is pretty darn stable itself. It just stays and stays and stays in your water, working hard, doing its job, and not getting used up (like all of those other deadbeat chemicals you use).

It’s because of this chemical longevity that you don’t need to add it very often to your pool, which is good news for your schedule and your wallet. The only caveat to this is if you use a combination product like stabilized chlorine. 

The Caveat & The Creep

Stabilized Chlorine (that we mentioned above) is a product that contains mostly chlorine and a dash of pool stabilizer in the mix. So, instead of adding chlorine regularly and stabilizer once a year, you actually are adding a bit of stabilizer whenever you normally add chlorine.

This method is convenient because you’re only having to add one product — killing two birds with one stone, as it were. (But why would you want to kill birds at all? I don’t understand that one.) With stabilized chlorine, you don’t need to add any extra stabilizer and your levels should stay where they need to be over time.

However, as with everything pool-related, it’s 100% necessary to test regularly, just to be sure your pool water is balanced. With high-quality pool water test strips, you’ll be able to check on your stabilizer levels whenever you normally test your water.

Weekly testing is especially important for pools that don’t get refilled very often. If you’ve tested and found that your stabilizer levels are higher than 50 ppm (parts per million) you may have developed “the creep”. No, not a weird guy with binoculars in the bushes. This term refers to stabilizer levels that have gotten too high, thus rendering itself (and chlorine) useless.

If stabilizer levels are too high, the chemical basically keeps chlorine from doing its job at all. There’s a happy medium here, a balance we need to achieve and 30-50 ppm is the happy place.

If your pool has developed “the creep”, you have two options. First, you can try just topping off your pool with some fresh water from your hose, which may be enough to solve the problem. If that doesn’t do the trick, you can also switch to non-stabilized chlorine and use pool stabilizer separately. 

How to Use Pool Stabilizer

In many aspects of life, it’s a good idea to read the instructions: board games rules, cooking recipes, or IKEA furniture-assembly. Usually, we recommend following the manufacturer’s instructions when it comes to pool maintenance too. Pool stabilizer is one giant exception.

Many pool stabilizer manufacturers will instruct you to add the chemical directly into your pool water — or maybe straight into the filter. Don’t do this. Remember, pool stabilizer is cyanuric acid… which is an acid. Although it’s a mild acid, it can still damage your pool equipment if it comes into direct contact.

The best method is to dissolve the pool stabilizer granules completely in a big bucket of fresh water before dumping the whole thing into your pool. Be patient while it dissolves, the timing will depend on the brand, consistency, and form of the stabilizer. But either way, you’ll be safeguarding your expensive pool equipment and also adding some extra water into your pool. 

When Not To Use Pool Stabilizer

As we mentioned above, using pool stabilizer in indoor pools is a waste of time and money. It can also actually hurt your chlorine’s productivity. Since indoor pools are not exposed to sunlight, the stabilizer is an unnecessary addition to your chemical soup and won’t actually do any good.

The same goes for hot tubs. If you own a hot tub, you probably already know how important it is to use a hot tub cover: to protect the chlorine in your spa, to keep the heat in, and to keep unwanted debris out. Stabilizer is completely unnecessary in hot tubs and should never be used.

A Stable Relationship

Otherwise, it’s fair game. Pool stabilizer, pool conditioner, cyanuric acid — whatever you want to call it, is a useful addition to any outdoor pool that will keep your pool cleaner and better sanitized by extending the life of the chlorine you put in and saving you money in the long run. 

By protecting the chlorine in your pool and giving it a longer life, you’re holding bacteria and algae outbreaks at bay, keeping your beautiful backyard oasis clean and pristine all year long.