Salt Water Hot Tubs: Pros and Cons

In recent years, Saltwater Systems have become a hot topic with their market claims of being a more “natural” or “chemical-free” alternative to sanitize your hot tub. Are Saltwater Systems better, though? Let’s look at the facts so you can make the best decision when purchasing your next hot tub.

The Origin of Saltwater Systems

During the 1980s, Saltwater Systems were first developed in New Zealand for swimming pools. Through a process called “electrolysis,” electricity was used to convert dissolved salt (sodium chloride) into chlorine or sodium bromide (which converts to bromine). In other words, Salt Systems convert salt into chlorine, and chlorine sanitizes the water. So, they are working as chlorine generators.

Generating chlorine or bromine from saltwater makes sense in the cool water of a swimming pool. Saltwater Systems are also a good alternative if a homeowner struggles with granular chlorine dosing or other chemical additives, such as UV inhibitors. While Saltwater Systems can be a good option for pools, there are some key differences tounderstand when considering an integrated Saltwater System for your hot tub.

Key Differences between Hot Tubs and Pools

Let’s start with the most obvious difference between hot tubs and pools, their size. The volume of water in a pool is very different from a portable hot tub; it is significantly less. In addition, hot tub water is typically much warmer than pool water (up to 104⁰F (40⁰C)). Increased temperature causes one to sweat more and release more organics, such as skin oil and bacteria, into the water.

The combination of less volume, more organics, and higher heat consumes sanitizer more quickly. To remain effective, a Saltwater System in a hot tub needs to generate—and maintain—a higher sanitizer concentration than it does in a pool.

Why Those Differences Matter

In the high-temperature environment of a hot tub, it is quite possible that a chlorine or bromine generator may not produce enough sanitizer to keep up with demand, especially when extra bathers are added to the mix. Some Salt System manufacturers even advise adding additional sanitizer to maintain safe water.

On the other hand, if the generator continues to run without bathers (meaning there are not enough dissolved organics to use up the extra sanitizer), it may overproduce chlorine. “Over-chlorination” may lead to excess chlorine gas trapped underneath the cover.

Not only can this degrade components such as foam pillows and the underside of the spa cover to the point of bleaching, but it also corrodes exposed metal accents, including stainless steel. This scenario is less likely because pools can more easily vent or “off-gas” than hot tubs, and have fewer internal components exposed such as jets.

Salt Systems and Hot Tub Components

If you live near the ocean or where icy roadways are salted, you may already know the pains associated with high salt levels. Salt causes corrosion and rust by attacking metal and breaking it down. When metal components inside a hot tub—such as heaters, heater elements, and jet escutcheons—are exposed to high doses of sodium, corrosion may occur. Salt corrosion shortens the lifespan of internal metal components, resulting in poor performance and costly repair bills.

In addition to your hot tub’s components, salt water can damage the surrounding area of your hot tub. Inevitably, some water splashes out of the hot tub while it’s being used, usually onto your deck or patio. Some major Salt System manufacturers say on their websites that if you don’t wash down areas where water has splashed out of a saltwater hot tub, you could experience a stained deck and damage to surrounding plants and shrubs.

Are Salt Systems Covered Under Warranty?

When it comes to aftermarket chlorine generators, and even those installed by the hot tub manufacturer, be sure to verify what is—and is not—covered under the manufacturer’s warranty. Some hot tub manufacturers could decline warranty coverage if an aftermarket salt sanitizer unit were to be installed instead of the manufacturer-installed units. Plus, corroded heaters and heating elements may not be covered under warranty if the damage is attributable to “chemical abuse.”

In other words, if a Salt System over-chlorinates the water and damages internal components, it may be attributed to “chemical abuse” and would not be covered under warranty.

As far as the Saltwater System itself, a one-year warranty is typical. By contrast, in-line sanitation systems (which do not use salt) such as ozone have a longer warranty period—usually between two to five years.

Are Salt Systems Less Maintenance?

Salt Systems are supposed to make sanitizing a hot tub “easy,” and manufacturers claim such hot tubs are “easier to maintain.” But are they really ‘set it and forget it’ systems? In reality a Saltwater System can take longer to start up than a standard water care system due to the time it takes to convert the salt into chlorine or bromine. The electrolysis process may take more than 72 hours to generate enough sanitizer to catch up with a family’s spa usage and may even require adding granular sanitizer or shock oxidizer to recover the water.

In addition, much like standard water care systems, a saltwater hot tub requires a multi-step routine to maintain it. These include salt test strips, balancing test strips and chemicals, metal and stain removers, spa cleaners, and pre-filters to reduce calcium, similar to a hot tub without a Saltwater System.

Water treatment systems are just one thing to consider when one is researching their next hot tub purchase. From starting the hot tub research/selection process to the hot tub install, a trusted Nordic partner would be happy to help you find the perfect hot tub for your lifestyle. To find your local authorized Nordic dealer, click here.

Want to do a little more research on your own before reaching out? Check out our Buyer’s Guide and blog posts for more hot tub insights.