What's The Problem With Chlorine Pucks?
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What's the problem with chlorine pucks you ask? Or at least I hope you ask. Or maybe you call them chlorine tablets or chlorine tabs instead. In any case I am happy you are asking because most pool owners don't know there is a problem with chlorine pucks until their pool suddenly turns green. Commonly, they might test the water for chlorine knowing that having no chlorine can lead to green water, but are surprised to see they have the normal amount of chlorine in the water that they always have except where the water is normally perfectly clean and clear, now it is green and murky - definitely no good for swimming! So what went wrong here? In a word, stabilizer. In other words that mean the exact same thing: water conditioner or CYA (cyanuric acid). All of these refer to the chemical component in your water which prevents the sun from destroying all of your chlorine every day.
A pool without stabilizer, or a CYA measurement of zero parts per million, would have no ability to resist the damaging effects from the sun and no matter how much chlorine you have in your pool, literally, you would lose about half of it every hour in the direct noon-strength sun. Chlorine is expensive so you combat this problem by adding Cyanuric Acid to the pool. The CYA acts as a sunscreen for your chlorine and when maintained at 30 to 50 parts per million will help you to hold the chlorine residual in the water and resist the damage from the UV from the sun. The problem that happens to many pool owners who use chlorine pucks is that eventually the CYA levels in the water climb over time. Every chlorine puck that you add to the water adds more CYA in addition to the chlorine, and without close monitoring the CYA levels will quickly climb and exceed the recommended range of 30 to 50 ppm.
Stabilized chlorine pucks - Chlorine pucks are stabilized so that they do not violently and rapidly oxidize, making them suitable for use as a slow release product, like in an erosion feeder. Unstabilized chlorine pucks (which do exist) in a similar erosion feeder would explode. It would require a special unstabilized chlorine puck erosion feeder to use unstabilized chlorine pucks. Also, note that mixing different kinds of chlorine in the same container would also cause an explosion. You can not even use a different style of chlorine after the first one is gone. You never, ever should mix chlorine types. This includes erosion feeders, buckets, mixing sticks or measuring scoops - nothing. Keep all kinds of chlorine 100% isolated from other chemicals, acids and types of chlorine. Chlorine pucks and chlorine tabs are commonly available as dichlor chlorine, or trichlor chlorine. Dichlor and trichlor chlorine tabs are almost 50% stabilizer which means you are adding large amounts of stabilizer to the water with each chlorine puck. Over time this CYA level will climb and eventually there will be a problem with water quality.
You can, and some people do, operate your pool with more than 30 to 50ppm of CYA. The most common application of this sees pool owners matching the ratio of free chlorine to CYA in the water, between 5% to 7.5%. So a pool with a CYA measurement of 100ppm would require between 5ppm and 7.5ppm of free chlorine. Less than this amount will likely result in green water. So where normally only 2ppm or so of free chlorine would be enough for a residential pool, you have to increase your free chlorine level as the CYA climbs or your chlorine becomes unable to function properly.
If chlorine pucks are a problem what to use instead? - Chlorine pucks inherently are not a problem, but instead a problem if you do not realize that climbing CYA levels need monitoring and occasional action such as partially draining and refilling the pool to get the CYA back to 30 to 50 ppm. It would definitely be an advantage to switch to unstabilized chlorine once you achieve the CYA of 30 to 50ppm as this will prevent from future corrective action (like draining and refilling) from being needed. Liquid chlorine is one great option. Unstabilized granular chlorine is another. Chlorine derived from a salt chlorine generator is also stabilizer free and another great option. If you are in love with chlorine pucks and want to continue to use them, you can also consider installing a cal-hypo puck feeder, a special erosion feeder for unstabilized cal-hypo chlorine pucks, and this will allow you the functionality and convenience of chlorine pucks without having to worry about constantly increasing CYA levels.
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Swimming Pool Steve is an award winning, second generation swimming pool specialist from Ontario Canada and one of the most trusted voices in the swimming pool industry. With over 20,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the Pleatco Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print. Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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