Salt systems for hot tubs are nothing new or revolutionary to the industry as some would like to have you believe. Manufacturers have been installing them for over 25 years along with the clout and interesting marketing claims ranging from softer skin to less maintenance to chemical free. However, with an initial price tag starting at around $700 and up to thousands of dollars, you should know some facts before you take the plunge into buying into the hype.
It’s just salt, like sea water, right? No. While standard sodium chloride or table salt (sometime sodium bromide) is an ingredient in the mix and the water is salty, the main sanitizer is good old chlorine. Using electrolysis, the sodium chloride molecule is broken apart into free chlorine ions and sodium carbonate. Chlorine is still doing most of the work.
Wait, chlorine is still in my spa? Yes. It is even recommended that salt system owners regularly add granulated chlorine to their hot tubs to maintain proper levels. One reason for this is that the “salt cell” should be kept on minimal settings in order to maximize the life of the cell (more on this later).
So, I just add a little chlorine here and there? No. The water chemistry nerd out there are probably already doing the math in their head after reading that other byproduct of the chlorine electrolysis is sodium bicarbonate. And what does sodium bicarbonate do? It raises the total alkalinity and the pH. In other words, hot tubs with salt systems have to have pH decreaser constantly added to them, no keep the pH from creeping too high. Further, all of the calcium in the water has to be taken out fo the water. This is to ensure that the electrolysis does not get gunked up with calcium deposits, which it eventually will.
How about maintenance? Because it is impossible to get all of the calcium out of the water, the residual in the water will build up on the chlorine producing cell, this means that it is obligatory to clean in every few months to prevent damage and to maintain output. This calcium build up is actually the main killer of the salt systems.
Other than all that, it does save money on chemicals in the long run? Not really. Pretty much all salt systems only have a warranty of one year, and after that you are responsible for paying the tech to come out and repair and install and salt cell in your spa, with is a fairly expensive service. After selling a variety of salt systems over the years we have only seen systems, that were properly maintained mind you, last for a maximum of a couple years. Most of the customers who had originally purchased salt systems, opted out of the repair and converted over to more standard sanitation recipes
All in all, salt systems can add a neat element of cleanliness and usually do a great job when they are running, but overall the purchase is fraught with downtime and expensive repairs. Not to mention the extra pH and calcium balancing. Many new sanitation systems are already on a lower chlorine regiment and also use a mixture of salt and minerals to keep the spa without using electrolysis. Just some food for thought.