Can You Put Chlorine In A Salt Pool?
If you have a swimming pool with an electronic chlorine generator (most pool owners just call it a salt water pool) then it is entirely possible, likely even, that you will need to add some chlorine at some point. This is completely fine for a "salt water pool" since this technology generates chlorine from salt so adding some chlorine manually is essentially the same thing as pressing a turbo button on your salt system. If this is at all confusing to you then you might still be in the group of pool owners that does not understand that salt water pools are chlorine pools - salt is not an alternative to chlorine in any way. Salt pools are chlorine pools. For more reading about this very important fact you can read this article about salt water damage to pools.
The next thing to know is that you do not have a salt water pool. Orcas swim in salt water pools...you swim in a pool equipped with an electronic chlorine generator. So what is the difference? About 32,000 parts per million of salt. Most people do not care to say "electronic chlorine generator" so perhaps the best short descriptor would be simply to call it a pool with a "salt system". When you say salt water pools you are actually describing something that does exists, but that is not what you have when you put 3000 ppm of salt in your pool and generate your own chlorine from this.
In understanding the terminology the answer to your question about whether you can add chlorine to a pool with a salt system should become clear...yes you can. It does not matter to the pool water how the chlorine is introduced - just that it is introduced. So in this sense you can add liquid chlorine, granular chlorine or even chlorine pucks to your pool if you have a salt system and this is no problem at all. There are a few considerations about which chlorine you add, and how you add it, but in short yes it is completely safe to add chlorine to a "salt pool".
Do salt water pools need chlorine? - Yes. Salt systems (electronic chlorine generators) make a very small amount of chlorine which requires them to operate for many hours in order to build up the correct amount of chlorine for your pool. For most pools you will be able to dial in on an appropriate power setting to generate the right amount of chlorine for the needs of your specific pool. So what happens when there is a sudden need for chlorine, like there was a big party with 10 times as many swimmers as the pool normally sees? Or what if there has been torrential rains for days on end? In these cases you should not attempt to wait for your electronic chlorine generator to slowly build back up the chlorine levels in your pool. Adding chlorine manually is the best option to get your free chlorine levels back up quickly before any algae, or something worse, has the opportunity to grow.
If you regularly add external chlorine to your pool to help maintain your free chlorine levels then you need to be aware of your stabilizer levels (CYA, cyanuric acid). The CYA level in your pool, when maintained at 30 to 50 parts per million serves to provide protection for your chlorine from UV degradation. Without enough CYA the sun will burn off the chlorine in your pool as fast as your salt system can make it. But if your CYA level climbs up to 80 or 100 parts per million you will find that your chlorine is no longer effective at killing bacteria and algae (known as chlorine lock) and the only way to resolve this will be to partially drain and refill your water. So adding chlorine to your salt pool is not a problem but you might want to give some consideration to which type of chlorine you choose and use one that does not have CYA.
The way that a salt water system works in a pool is that is generates chlorine slowly over a long period of time. If you wait for the salt system to generate your chlorine you may find that the bacteria and algae in the water grow as fast as your system can generate chlorine. This is especially true if you have high phosphate levels. Many salt system manufacturers list phosphates as over 500 parts per billion as a cause for reduced system efficiency, and phosphates over 2000 parts per billion to be too high for the salt system to operate at all. If your chlorine is used up as fast as you are able to make it with your salt system then your pool will surely turn green, and the best way to deal with this is to shock with chlorine.
It is also important to add chlorine to your salt pool to occasionally burn off the chloramines in the water, as well as to kill cryptosporidium which is one of the hardest things in your pool for chlorine to sanitize. This is why sustained periods of free chlorine above 10 parts per million are required. Using a UV, ozone or AOP system is another way to help eliminate the risk from crypto in your pool without needing to raise your chlorine levels so high...and these also work to eliminate chloramines form the water. Just a few of the reasons that these systems are so popular for supplemental use in addition to chlorine or salt systems.
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UV system reviews
Ozone system reviews
Ionizer system reviews
Do pools really need chlorine?
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