Are Salt Water Pools Safe?
Are salt water pools safe? In short, a salt water pool is every bit as safe as a traditionally maintained swimming pool that is sanitized with chlorine. The reason is simple...salt water pools are chlorine pools. The most important thing to understand is that chlorine kills almost all bacteria and pathogens in pool water in less than 60 seconds at a concentration of just one part per million of free chlorine. This is why chlorine is used versus many other sanitizing or oxidizing chemicals. In fact chlorine has four specific properties that make it the ideal choice as a sanitizer in swimming pools:
1) Chlorine is a sanitizer
2) Chlorine is an oxidizer
3) Chlorine is an algicide
4) Chlorine can hold a residual value in the water
Collectively these four properties allow for the safest possible swimming environment when used and maintained properly. So how does this relate to salt water? Quite simply a salt water pool is a chlorine pool. They are not different things - chlorine and salt water pools are both the exact same in that they rely on free chlorine in the water to kill bacteria, viruses and organic debris. The only difference is how you get the chlorine into the water. With a traditional chlorine pool you would simply add chlorine directly to the water. You would do this with liquid chlorine, granular chlorine, or chlorine pucks. Regardless of how you add the chlorine to the water the end result is that you develop a free chlorine residual in the water.
When it comes to salt water pools the most important thing to understand is that the pool is still a chlorine pool. Instead of buying pre-made chlorine in the form of liquid or granular or chlorine pucks, you are essentially buying a chlorine generation system. Chlorine is made from salt - sodium chloride. If you add enough salt to the water in your pool you can generate your own chlorine as needed instead of buying it and adding it manually. This process is completed via electrolysis by the chlorine generation cell that comes as part of a salt water system.
Salt Water & Chlorine Are The Same Thing
In order to consider yourself an informed consumer the first thing that you need to know about salt water versus chlorine is that there is no difference at all other than how you are physically adding chlorine to the water. With a traditional chlorine pool you are adding chlorine directly to the water. With a salt water pool you are adding salt, and then generating chlorine as needed via the electrolysis cell. In the end result both pools are protected by chlorine so a salt water pool is every bit as safe as a traditional chlorine pool.
There certainly are some differences between salt water and traditional chlorine pools, such as the method in which the chlorine is added. With a traditional pool when you need chlorine you simply add chlorine manually and raise the free chlorine value. Since it is not entirely convenient to add chlorine every day, the typical dosing schedule would have you add more chlorine than is needed, and this value would slowly come down over the following days. This is one of the ways that a salt water chlorine pool may be better (and safer) than a traditional chlorine pool. Instead of adding more chlorine than needed, and then letting that value drop near to zero, a salt system can be calibrated to create just the right amount of chlorine needed for a specific pool. While this may take a little time to fine tune, the end result is that the peaks and valleys of adding chlorine manually can be replaced with a steady stream of chlorine and more stable free chlorine levels. This can be very useful for pool owners who are sensitive to chlorine and who like to avoid unnecessarily high levels of chlorine exposure.
Remember that only one part per million of chlorine will kill almost any bacteria or pathogens in the water within 60 seconds so there is not much value in having levels higher than this. The only reason why you would typically maintain levels higher than this is to develop a chlorine reserve. Since you never want your chlorine level to fall all the way to zero, you want your levels to be high enough to withstand a busy day of swimming, or a heavy downpour of rain, without falling to zero. If it were not for this, then only one part per million would be enough in all pools. With traditional chlorine treatment it would be common for a pool to fluctuate between one PPM and five PPM. With a salt chlorine generator you can get much closer to maintaining one (or two) PPM of chlorine at all times. Since you are being exposed to less peaks and valleys of chlorine value, and the chlorine level (in theory) should never drop to zero, it is reasonable to say that salt water pools might even be safer than traditional chlorine pools. The same can also be said for how salt pools require you to handle only salt, and even this is only done once or twice per season. Traditional chlorine pools require that you buy, transport, and store large quantities of chlorine which is certainly more of a hazard than occasionally buying a bag of salt to add to the water.
Pros & Cons Of Salt Water Pools
As described above there are some specific advantages of salt water chlorine pools versus traditional chlorine pools. They tend to have less peaks and valleys in terms of how much chlorine is in the water, and you do not need to buy and store chlorine anymore. Salt water also feels softer on the skin and less drying than traditional chlorine pools. In these ways salt water pools are easier than chlorine pools however it is critically important to understand that they are still a chlorine pool, and they are absolutely not maintenance free as some sale people might suggest to you.
Salt water pools require every bit as much care and maintenance as a regular chlorine pool, with the sole exception that the chlorine delivery is automated. This does not mean that you set it and forget it - this means that you adjust the amount of chlorine you want in the water by setting the output from your chlorination cell. All other typical pool care and maintenance remains the same, from brushing, skimming, and vacuuming, to the pH and total alkalinity balancing. If you buy a salt water system for your pool because you want a hands free approach to maintaining your pool then you will likely be very disappointed with the results.
In particular it is worth noting that chlorine comes in many different pH levels. Some has a very low pH while others, like salt water systems, have a very high pH. The further the pH is from neutral (7.5) the more adjusting you will need to do to keep your pH levels in the correct range. This is one of the disadvantages of salt water systems in that the chlorine made from salt water has an extremely high pH and this results in the pH of the pool chronically being too high. This has a number of adverse reactions on the pool:
Lowered Chlorine Effectiveness - The ideal operating pH for chlorine is much lower than what you would ever want your pool to be. A pH of around 4 to 5 would be the best for allowing chlorine to work effectively however you would certainly not want to swim in water with a pH level like this. At 7.2 to 7.8, the range for pool water pH, chlorine is less effective than ideal pH levels, but still effective enough to keep the water clean and safe. At high pH levels, like above 8.0, chlorine is vastly reduced in its ability to kill bacteria. Even with an established chlorine reserve of a few parts per million, the chlorine is not able to kill bacteria effectively. Above a pH of 8.2 the chlorine is over 90% inactive in the water. This is a very real concern for salt water pools as salt water pools tend to have chronically high pH levels. Learning how to manage the pH in a salt water pool is critical for the safety of the swimmers and well being of the pool and equipment.
Increased Scaling & Potential For Damage - There is a calculation that can be done which determines what "state" water is in, whether it be an acidic state, neutral state, or a scaling state. This is a formula called a saturation index and for the most part it is not something that residential pools need to deal with where as commercial pools and industrial water systems would need to deal with the saturation index of the water much more frequently. In short, there are factors which can increase the likelihood for water to enter a scaling state where scale will form on pipes and plumbing equipment. Some of these factors are calcium hardness levels of the water as well as the temperature of the water. The pH is also one of the main factors used to calculate saturation index, and it is very likely that a salt water pool with a high pH level will be in a scaling state. This means that scale will readily form on plumbing lines and inside of your pool equipment where it can very quickly cause permanent damage.
Increased Water Conductivity - In order to make a primary battery you would immerse dissimilar metals into a salt water solution. The resulting chemical reaction will allow you to measure a potential difference (voltage) across these metals. Pure water does not conduct electricity. It is the impurities in the water that allow electricity to conduct through the water. Increasing the salt content in the water by tenfold allows for a tenfold increase in the amount of current that leaks through the water between these dissimilar metals that make up your pool system. These are tiny values that pose no risk to swimmers, but as part of an electromechanical process called galvanic corrosion, this constant trickle of current causes one of the metals to deteriorate (corrode) at an advanced rate. If not controlled this destructive process can cause significant and expensive damage to your pool.
So yes, salt water pools are safe...at least as safe as chlorine pools since they are essentially the same thing. They are not, however, maintenance free and there is in fact some concerns for damage to your pool which can happen with salt water pools. For most pool owners salt water is still a good choice, but before you make the conversion you need to become more informed about the risks. Now that you know a salt water pool is safe, you can read some of these articles which discuss the concerns with salt water pools:
Is Salt Water Bad For Pools?
Tips For How To Maintain A Salt Water Pool
Pool & Spa Water Chemistry Crash Course
Salt Water System Reviews
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