Understanding Saltwater Pools
By Debra Maurer
Due to their growing popularity in the past few years, you may have heard of saltwater pools, but unless you own one, you may be wondering how they work and if purchasing a saltwater chlorinator is a water care option you might consider for your swimming pool. Read on to learn how water is effectively sanitized and maintained with a saltwater chlorinator.
First of all, what is a saltwater chlorinator?
Also known as a chlorine generator, a saltwater chlorinator converts salt to chlorine for effective and automatic sanitization. This means that you don’t have to add chlorine; instead, you add several bags of quick-dissolving, specially manufactured salt to your swimming pool at startup, and typically a few times a year, as needed. A saltwater pool is not chlorine-free, but its eco-friendly draw comes from never having to buy, store, or handle chlorine.
If a saltwater pool contains chlorine, how is it different from a traditional chlorine pool?
In a swimming pool with a saltwater chlorinator, the free chlorine is created during the conversion (or electrolytic) process. Because chlorine is produced constantly, strong-smelling chloramines (the byproducts responsible for that “chlorine smell”) are unlikely to form, allowing for a more pleasant environment. After the chlorine is used to sanitize, it reverts back to sodium chloride (salt), so most of the swimming pool water contains saline rather than chlorine.
Won’t the water feel like I’m swimming in an ocean?
The salinity is actually gentle to the skin and eyes because the salt levels are relatively low—about half that of a human tear drop (a concentration of 0.5 percent). At recommended salt levels of 3,000 – 4,000 ppm—compared to an ocean’s 35,000 ppm—the pool water doesn’t taste salty or make your skin feel sticky, though you may want to wear goggles if swimming in the pool for extended periods.
How exactly is the salt converted to chlorine?
Chlorine is produced due to a reaction in the unit’s electrolytic cell. You first add salt that is produced specifically for salt chlorinators. As the salt dissolves and the water circulates, it passes through the cell and becomes free chlorine. “The process of producing free chlorine (hypochlorous acid) and sanitizing the water happens in one place—the cell,” says David Pruchniewski, field applications engineer at Goldline Controls, a Hayward Industries company that manufactures salt chlorinators and other pool equipment. “After that, the chlorine converts back to a mild saline solution (sodium chloride and water) to be reconverted to chlorine again as the process repeats.”
The swimming pool water is sanitized continuously as long as the pump is running, and one bag should keep the salinity at the proper level for at least several months. Levels drop gradually due to splash-out and backwashing only—evaporation will not reduce the salt content.
How do I maintain a saltwater pool?
Most saltwater chlorinators have a digital control panel that provides the most current salt reading. Recommended salt levels are specific to the actual system you purchase, but generally speaking, the ideal salt level is 3,000 – 4,000 ppm. If levels dip below 3,000, use a manual test to make sure the levels are correct before adding more salt. On occasion, a pool can actually be so oversalted that it will not produce an accurate reading. If that’s the case, the last thing you want to do is add a giant bag of salt! If you add too much, and the salt level exceeds 4,000 ppm, the pool must be partially drained, then refilled with hose water. (Note that draining of any kind must be done under the guidance of a professional to prevent serious damage to the pool structure.)
While sanitizer, total alkalinity, and pH levels should still be monitored regularly (at least once a week), “it’s much easier to maintain a chlorine level of 1 – 4 ppm in a saltwater pool because the chlorine is being produced constantly, as long as the pump is on,” says Bob Harper, general manager of Pristiva, which produces the Pristiva™ two-step system for saltwater pool care. “You also want to use purer forms of salt to ensure clear pool water, prevent corrosion, and minimize scale buildup on the generator’s cell.” Impure forms of salt may contain metals, notes Pruchniewski, which can lead to stains on the pool surface. As with all pools, it’s a good idea to take a water sample to your pool supply store about every month to check for proper water balance, total dissolved solids, and the presence of metals, says Harper.
Because the chlorine produced is unstabilized, a stabilizer, such as cyanuric acid, is added to maintain a chlorine residual, unless the pool is indoors. If you have a chlorine generator and you run the pump during off-peak times (usually 9 pm – 9 am), you should run it for about two hours in the daytime during hot, sunny days to avoid algae blooms. (Remember that chlorine is not produced when the pump is off.) If you have a newer variable-speed pump, this should not be an issue as the pump can run 24/7 on the lowest speed.
How do I know if a saltwater chlorinator is right for my pool?
The type of pool you own and its surrounding materials and equipment are important—and experts’ opinions vary. “Other than stainless steel, which is rarely used in today’s pools and equipment, I have no concerns with the ability of other finish materials to withstand salinated water over time,” says Bob Harper, general manager of Pristiva. If using natural stone around the swimming pool, Harper advises speaking with stone suppliers on how to properly prepare it for exposure to saltwater.
However, Thomas Lopez, president of Aquavida Pool Remodeling, Phoenix, Ariz., notes that saltwater chlorinators may pose a risk to stone and other finishes: “If you’re adding a salt system to an existing pool, it should be gunite or vinyl-lined and have either faux rock or concrete around it. Salt can eat away at natural stone and cause etching to grout used around boulders and tile.” If you plan to install a fiberglass swimming pool, it’s important to choose a builder who uses high-quality materials and is aware of which saltwater chlorinators are safe for its surfaces over time.
When installing a saltwater chlorinator, experts recommend using newer swimming pool equipment because current pumps and heaters are designed to withstand exposure to saltwater, now that salt systems are more prevalent. “Older equipment could be susceptible to corrosion so you may want to replace it or contact the manufacturers,” says Lopez.
If you plan to make the switch or integrate a saltwater system into a new swimming pool, make sure your pool builder is knowledgeable on the subject, and ask for any references from customers who have been using a saltwater chlorinator for a few years.