Just what is a so-called "saltwater pool"? There is confusion over this term because there are pools in the world that use water from the ocean. These are known as seawater pools, which are filled directly from the ocean and contain 30,000 to 40,000 ppm of salt. This is different from a saltwater pool. Saltwater pools are filled with fresh water and then 3,000 to 4,000 ppm of pool-grade salt is added, forming the basis for liquid sodium hypochlorite pool sanitation. The difference between pool salt and bulk salt is that it is especially formulated without caking agents and other additives. The name "saltwater pool" is a great misnomer, and hundreds of pool owners were sold on this misconception, believing they had a "chemical-free" pool that was nothing but salt — even though chlorine is still used to disinfect water and kill bacteria. A more correct term for saltwater pools is a pool with a salt chlorine generator. Saltwater pools have units installed in the plumbing system that are designed to take the salinity within the fresh water and convert it into a pure form of liquid chlorine, which is a form of water treatment and water disinfection for pool water. So, a saltwater pool is a system designed to produce chlorine chemically in the same way that large-scale chlorine producers manufacture it.
In the early 1800s, William Cruickshank experimented with a homemade battery and sodium chloride NaCl. The result was the electrolysis of the NaCl split the molecule into pure chlorine gas and sodium hydroxide. This was a very primitive method that led to the development of the chlor-alkali industrial method for making chlorine. Primarily, this method is used to create liquid sodium hypochlorite. Inside a saltwater generator, electricity is sent through metal plates to trigger a process called electrolysis, producing liquid chlorine for pools. This is the functional opposite of a battery: here, the positive plate (anode) generates pure chlorine gas, while the negative plate (cathode) produces sodium hydroxide, effectively sanitizing the pool water on the spot.
These combine in the flow stream and create sodium hypochlorite or liquid chlorine. So, yes that “salt” in the water is there to create a highly effective chemical for disinfection of the pool. That chemical is chlorine and it is one of the most effective products used to keep pool water safe for people.
For the most part, saltwater chlorine generators are sufficient day in and day out to keep pool water chlorinated and clean. There are times, due to an excess of swimmers or environmental contamination such as wind or rainstorms, higher levels of chlorine are needed. This is known as chlorine demand. In many pools, the demand outweighs the amount of chlorine coming from the saltwater generator. Most saltwater generators are designed to put out a fixed amount of chlorine. This fixed amount of chlorine may not be enough to handle a sudden large organic load. The recovery time from the unit may be too great. If it takes a unit six hours to recover from a contamination influx on a scorching summer day, that could lead to unsafe conditions developing from the presence of bacteria or algae growth. In these cases, additional chlorine can be added separately to supplement the unit, sometimes requiring breakpoint chlorination and other shock practices. Some other reasons that additional chlorine may be needed could be if the unit breaks down or is under repair for some time.
There are several types of chlorine which may be used as an additional shock in saltwater chlorine generator pools. Before selecting a chlorine shock product for saltwater pools, it is important to know what the by-product from that product is and how it will affect the generator. Calcium hypochlorite is a commonly used shock product, but compared with liquid pool sanitization treatments it can introduce more challenging byproducts. However, the use of calcium hypochlorite to shock a saltwater pool can lead to an increased amount of calcium which can cause scale formation on the cells of the generator. Scale formation on saltwater generator cells will reduce the output of the generator and can cause premature failure. Even if calcium-based shocks are not used, there is still a certain level of natural calcium in the water that at higher levels can still lead to scaling of the cells. Many salt chlorine generators incorporate a reverse polarity setting to knock the scale off of the cells. However, the knocked-off scale can enter the pool and settle on the floor as white flakes. The best way to prevent scale formation in salt chlorine pools is to incorporate the use of sequestering anti-scale product such as Orenda SC-1000. The SC 1000 is preferred because it is a phosphate free approach and has long staying power.
Trichlor and dichlor types of shock are chlorine that contains significant amounts of cyanuric acid stabilizer CYA. The byproduct of these types of shock is the accumulation of the CYA. Higher levels of CYA can reduce the effectiveness of free chlorine in the pool water. High CYA can also interfere with the unit’s ability to produce sufficient chlorine to keep up with demand.
Liquid pool chlorine, which is sodium hypochlorite, is an effective shock for saltwater pools and remains one of the most reliable pool sanitizers.
First, because it is in liquid form, it acts immediately to attack bacteria and algae with a powerful sanitizing agent, which is why many service professionals rely on liquid chlorine for pool maintenance.
Next, it acts as an oxidizer to help reduce organic contamination and swimmer waste, providing both disinfection and oxidation during shock treatment.
And finally, the by-product from liquid pool chlorine is simply sodium chloride or salt, underscoring that liquid chlorine is simply sodium hypochlorite used safely in water treatment.
Liquid chlorine will not contribute to calcium increase, so the cells will not scale up, making it especially suitable for shock chlorination in saltwater pools. Also, liquid chlorine contains no CYA, so it will not cause any reduction in the effectiveness of the chlorine sanitizer, unlike many stabilized chlorine tablets.
In the case of heavy rains where the salt may have been diluted, a shock of liquid sodium hypochlorite can help raise levels immediately until more pool salt is available to add.
Also, sodium chloride as a byproduct and part of total dissolved solids TDS will not lead to scale formation, cloudy hazy water, or poor disinfection. Simply put, the byproduct of liquid chlorine compared to other solid types is the most harmless.
Liquid pool chlorine is one of the best choices for shocking a saltwater pool due to its power and purity to keep saltwater pools safe, clean, and clear, and many pool owners ultimately switch to liquid Sani-Clor® chlorination or use Sani-Clor® liquid chlorine for both sanitizing and shock.
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Author: Terry Arko
Terry Arko brings more than 40 years of experience in the recreational water industry and currently serves as Technical Content and Product Training Consultant for HASA Pool, makers of HASA Sani-Clor. His career spans service and repair, retail sales, chemical manufacturing, technical service, commercial sales, and product development—giving him a uniquely comprehensive perspective on water chemistry from both the field and the lab.
A respected educator and thought leader, Terry has written over 200 published articles on water chemistry and has been teaching chemistry-focused courses for more than 30 years. His ability to translate complex science into practical, real-world understanding has made him a trusted resource for pool professionals seeking safer, smarter, and more consistent water care.
Terry is a Certified Pool Operator (CPO) Instructor with the Pool & Hot Tub Alliance (PHTA) and serves on the Recreational Water Air Quality Committee (RWAQC). In 2025 he was presented the Pool Nation Lifetime Achievement Award. Terry is driven by a lifelong commitment to education, innovation, and advancing industry standards through knowledge.