In recent years, saltwater 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 Saltwater 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 saltwater 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.
Differences between Hot Tubs and Pools
Here are some differences to consider when comparing the average hot tub with the typical backyard pool:
The average hot tub, at only 400 gallons, 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 and more organics means that sanitizer is consumed more quickly.
Open pools allow sanitizers to vent (or, “off-gas”) whereas hot tubs are covered when not in use.
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 or co-bonded polymer shell.
Water in an open pool is exposed to more natural UV light than in a hot tub.
Why the Differences Matter
Four people in a 20,000 gallon pool is obviously much different than four people in a 400 gallon hot tub. Four people in a 400 gallon hot tub is equivalent to 200 people in a 20,000 gallon pool! 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 period of time. “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, it may corrode exposed metal accents (including stainless steel), and/or dull the color of hot tub acrylic surfaces.
Salt 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 salt sanitizer 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.
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.
The Seattle Hot Tub Company Approach to Water Care
At Seattle Hot Tub, we believe that technological advancements are great as long as they work as advertised. Marquis' 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’ considered to be safe by the pool and spa industry. 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?
The fact of the matter is that spa water needs to be sanitized in order to be safe. With nearly 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 Signature, 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.