In recent years, hot tub salt water systems have flooded the market claiming to be the “natural” or “chemical-free” alternative to sanitize your hot tub. But are these claims accurate? Are saltwater systems really better? Let’s consider the facts so you can make the best decision when purchasing your next hot tub.
History of Hot Tub Salt Water Systems
Saltwater systems were developed for swimming pools around 1980 in New Zealand. Through a process called “electrolysis,” electricity is used to convert dissolved salt (sodium chloride) into chlorine or sodium bromide (which converts to bromine). In other words, a salt water system—by design—generates the same chemical sanitizers used in non-saltwater systems.
Generating chlorine or bromine from saltwater makes sense in the cool water of a swimming pool, especially if a homeowner struggles with granular chlorine dosing or other chemical additives, such as UV inhibitors. But there are more than a few reasons why saltwater systems are not the best fit for hot tubs.
Salt systems convert salt into chlorine, and chlorine sanitizes the water. So, it’s more accurate to call salt systems what they are: chlorine generators. Once you understand that it makes a lot more sense.
Differences between Hot Tubs and Pools
Here are some differences to consider when comparing the average hot tub with the typical backyard pool:
- At only 400 gallons, the average hot tub is much smaller than a pool.
- Hot tub water is much warmer, up to 104⁰F (40⁰C), causing bathers to sweat more and excrete more organics.
- Less water, more organics, and higher heat consume sanitizer more quickly.
- Slow regeneration of sanitizer causes problems more quickly in a hot tub.
- Open pools allow sanitizers to vent (or, “off-gas”) whereas hot tubs are covered when not in use. Excessive chlorine traps excessive chlorine gas, which may cause damage.
- Unlike most pools, hot tubs have internal metal components such as water heaters, heater elements, and jet face escutcheons (the metal rings around the jets).
- Pools are typically made of fiberglass or concrete, whereas hot tubs have an acrylic shell.
- Water in an open pool is exposed to more natural UV light than in a hot tub.
Why the Differences Matter
Two people in a 10,000-gallon pool (37,855 litres) is obviously much different than two people in a 400-gallon hot tub (1,515 litres). Less water volume means a higher concentration of dissolved organic compounds (such as sweat, skin oil and bacteria) which uses up sanitizer more quickly. So to remain effective, a saltwater system in a hot tub would need to generate—and maintain—a higher sanitizer concentration, not a lower one. Is this what really happens?
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. In fact, some salt system manufacturers admit you may have to add additional sanitizer to properly maintain safe water!
If the generator continues to run without bathers (meaning there is not enough dissolved organics to use up the extra sanitizer), it may actually overproduce chlorine for a while. “Over-chlorination” may lead to excess chlorine gas trapped underneath the cover. Not only can this degrade foam pillows and the underside of the spa cover to the point of bleaching, but it may also corrode exposed metal accents (including stainless steel), and/or dull the color of hot tub acrylic surfaces.
Hot Tub Salt Water Systems and Hot Tub Heaters
When salt is added to spa water, it is not immediately converted into sanitizer (through the process of electrolysis). Many salt system manufacturers claim the amount of salt is at a “minimal level” in the water. However, salt systems require about 1,750 to 3,000 parts per million to work, or about triple the amount of salt found in tap water. You can estimate about 10 or more cups of salt for a 400-gallon hot tub, or about 2-1/3 cups of salt per 100 gallons. Why does this matter?
Ask anyone living near the ocean or where icy roadways are salted, and they will tell you about their issues with metal corrosion. 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 sodium doses corrosion may occur. This can shorten the lifespan of internal metal components, resulting in poor performance and costly repair bills.
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 decline warranty coverage if an aftermarket hot tub salt water systems unit was installed instead of the manufacturer-installed unit. Plus, corroded heaters or 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” which is not typically 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) have a longer warranty period—usually between two to five years.
Do Salt Systems Require 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 because of the time it takes to convert the salt into chlorine or bromine. In fact, 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.
What about the surrounding deck or patio? Inevitably, some water splashes out of the hot tub while it’s being used. 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. But ask yourself: “Do I really want to hose down my patio, deck or surrounding backyard after I’ve spent a relaxing evening in my hot tub?”
Last but not least, manufacturers tout that “properly-maintained” saltwater can be kept for up to a year, and that salt cartridges only need replacing every 4 months (or 120 days). However, much like standard water care systems, a saltwater hot tub requires a variety of water care products to properly maintain it. These include salt test strips, balancing test strips, balancing chemicals, metal and stain removers, spa cleaners, and pre-filters to reduce calcium. Clearly, the whole “less maintenance” claim doesn’t hold much water.
Expert Advice from a Hot Tub Industry Veteran
Bill Wells, Marquis National Sales Director, has observed the saltwater debate for over 25 years. “Salt systems sound great, but the devil is in the details,” he cautions. “Marquis has explored salt technology repeatedly, looking for benefits that outweigh the problems inherent with salt. But we keep arriving at the same conclusion: salt makes it harder, not easier to own a hot tub.”
“Unfortunately, saltwater hot tubs have been marketed as a mystical, magical thing,” he continues, “giving people the false impression that salt sanitizes the water. But it doesn’t. That’s not how it works. Salt systems convert salt into chlorine, and chlorine sanitizes the water. So, it’s more accurate to call salt systems what they are: chlorine generators. Once you understand that it makes a lot more sense.”
From a technical perspective, he adds: “Salt systems are supposed generate chlorine in the range of 3 to 5 ppm (parts-per-million). But they are slow to react to bathers in the water, so they continue generating chlorine as high as 10ppm. That will shorten the lifespan your foam spa pillows and spa cover, and probably irritate people with sensitive skin. In contrast, the Marquis in-line sanitization system maintains about 0.5 to 1ppm. In other words, you get a lower concentration of chemicals with Marquis. Safe, clear, odorless water, and none of the issues inherent with salt.”
Consequently, he feels very comfortable recommending the Marquis ConstantClean+ system to dealers and consumers alike. “The goal of a hot tub is relaxation and enjoyment, not a headache to maintain. ConstantClean+ is the simplest and easiest system, with the lowest chemical concentration. You look at the test strip, and if it’s good you’re good. If the sanitizer is low, you adjust your cartridge. And if the cartridge is empty, you replace it. Simple.”
Marquis has explored salt technology repeatedly, looking for benefits that outweigh the problems inherent with salt. But we keep arriving at the same conclusion: salt makes it harder, not easier to own a hot tub.
Why Marquis Hot Tub Water Care is Better
At Marquis, we believe that technological advancements are great as long as they work as advertised. Our engineers continually research and test available technologies to determine whether or not they can be recommended. But as we have seen, the claim that salt systems are “natural,” “chemical-free,” or “maintenance free” is simply not accurate. Salt system technology produces the very same ‘natural chemicals’ used in Marquis hot tubs. But given the negative impact of salt on internal hot tub components, the potential warranty issues, and the added maintenance concerns, does a saltwater system really make sense?
Spa water needs to be sanitized to be safe. With over four decades of hot tub manufacturing and proper hot water maintenance experience, Marquis remains convinced by best practices which have stood the test of time. Namely, smaller controlled doses of bromine or chlorine, an ozone generator, and perhaps spa minerals (or conditioners) to soften the water. These methods not only ensure safe water, but serve to protect your hot tub components over time to deliver The Ultimate Hot Tub Experience!®
Marquis Crown Collection, Signature Series, Vector21 and Marquis Elite series hot tubs offer a high-end, self-dispensing water treatment system specifically designed to slow dose a hot tub to the right level. Marquis has partnered with Frog®, one of the leading manufacturers of sanitizers and natural minerals, to sanitize and soften the water. Pairing Marquis® chemicals and spa care products with your hot tub ensures clean, safe, and easy water care. You can sit back, relax, and soak away the troubles of the day, confident in the pristine water surrounding you. For the best water care available, visit our ConstantClean+ section to learn more about the best water management system on the market.