Salt water chlorination. Pros and cons.

During the last years, the use of salt water chlorination in swimming pools has got a great increase due to the big advantages of this kind of chlorination. However, you must know very well its characteristics before deciding to install this method of chlorination in your swimming pool, because the idea that "you must add salt to the swimming pool and forget about it", is not exactly.

How does salt chlorination work? 

It consists of adding salt (ClNa) to the swimming pool to obtain a concentration of 3.000 ppm (sea water has a concentration about 38.000 ppm). Once salt is dissolved, water passes through an electrical current between two electrodes to produce the electrolysis of the salty water. In this process, sodium (Na) and gas chlorine (Cl2) are produced.

If pH is between 7.1 and 7.3, this chlorine will combine with water to produce hypochlorous acid that is the bacteria-killing form of chlorine, exactly the same product obtained adding liquid chlorine. So this method consists of the chlorine production "in situ".

Salty water swimming pool maintenance.

Salty water swimming pools need more or less the same maintenance that a traditional chlorine swimming pool, against the “maintenance-free” idea that sellers usually give us. The general maintenance works that we must carry out to have a perfect salty water swimming pool are: 

  • First, it is necessary to test water chemistry in order to keep it balanced (pH, hardness and alkalinity) adding the proper products to adjust it (calcium chloride, bicarb of soda, sodium bisulfate and muriatic acid), in order to obtain the maximum production of the killing part of the chlorine.
  • Also, we must keep on measuring the free chlorine and combined chlorine to control chlorine levels.
  • Regular superchlorinations must be performed as well, which will have to be done by liquid chlorine since salt chlorine generators doesn’t allow a massive chlorine production to have a shock effect in the water.
  • Another effect to control is the chlorine destruction by contact with ultraviolet light (sun). In a very sunny swimming pool, we’ll have two options to mantain chlorine levels:

- 1st option: To increase chlorine generator working time, that is to say, to produce more chlorine to make up for the chlorine destruction by ultraviolet rays. This option will increase electricity consumption and electrolytic cell wearing out. 

- 2nd option: To protect chlorine from this destruction adding chlorine stabilizer (cyanuric acid), which we can find in chlorine in tablets (dichlor or trichlor). This option is correct, but it should be the last one to take because one of the advantages of this kind of sanitizing is the elimination of extra additives that are present in swimming pools products. 

In the other hand, there will be some specific tasks for a salty water swimming pool that are the following ones:

  • Monitoring and adjustment of salt concentration, which must be kept between 3,000 and 4,000 ppm (depending on the manufacturer's recommendations). 
  • Checking and cleaning the salt chlorine cell, because a dirty cell will decrease a lot the chlorine production. Besides, if this cell is not properly mantained it will deteriorate very quickly and it will have to be replaced.
  • Special care in the control and adjustment of the pH. In case of salt chlorination, to adjust pH is much more critical since if it’s too high there will be more calcareous depositions in the electrodes of the electrolytic cell, which will decrease the production of chlorine and will increase the cleaning needs of the electrodes. That is why it’s recommended the installation of an automatic controller of pH and a self-clean salt chlorine generator. 
Things to keep in mind before installing a salt chlorine generator. 

According to all this information, salt chlorination is a good option for a swimming pool, but it’s necessary to study every single case before deciding on that. So, we can draw the following conclusions, according to our experience:

  • Salt chlorination and chlorination by liquid chlorine are equivalent regarding to water chemistry, because there is no addition of other substances as cyanuric acid for the chlorine protection from ultraviolet rays. So, we believe that these chlorination systems present fewer health risks than the addition of chlorine in tablets.
  • The main advantage of salt chlorination compared to liquid chlorination is the elimination of the purchase and transport of liquid chlorine, which might be a hard work.
  • Economically speaking we’ll have to analyze the costs, to know if it’s going to be a good investment. The costs to consider must be:
    • Salt Chlorine generator installation cost, including a pH automatic controller. 
    • Cost of cleaning and replacements of electrolytic cell (usually they last a maximum of three years). 
    • Power consumption of the Salt Chlorine generator depending on the estimation of working hours.
    • Cost of the salt. 
    • If the swimming pool is very sunny, we’ll have to add the cost of the chlorine stabilizer to make up for the chlorine destruction by ultraviolet rays.

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