What is a Saltwater Hot Tub?

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How They Work and Why You Should (or Shouldn’t) Convert Your Spa

Saltwater Hot Tubs Explained

Saltwater Systems for Hot Tubs

What comes to mind when you think of salt water spas?

Some think of a contained version of the ocean.  But for me, I’ve always envisioned a fountain of youth and vitality and some of the most restorative places on Earth: volcanic hot springs on Greek Islands; natural healing resorts in the desert; the mineral-rich Dead Sea.

So, naturally, we want a backyard version. A blissful, bubbling, salty hot tub that requires no chemicals, little maintenance, and makes us look and feel 10 years younger, right?

Unfortunately, that’s not exactly how a saltwater hot tub works.  While there is salt in spa water, the whole idea behind it is less about minerals and more about chemistry.  Inside each saltwater hot tub (or pool, for that matter) is a salt water converter, a system that changes the salty water into a chemical that keeps your water clean and sanitary.

The good news is that you don’t need to purchase a brand new “salt water spa.” You can convert your existing tub to salt without even hiring a service technician!  Before you run out and purchase a new salt system and switch your spa over to salt, read more about how it all works and salt water hot tubs pros and cons.

How a Saltwater Spa System Works

Salt system in hot tub

The system is made up of a power/control box with a cell that converts salt into sanitizer (aka chlorine).  Salt systems are an advanced way to have natural chemistry to work in your favor to disinfect your hot tub.  We’re going to get technical for a minute to explain the full process a salt water system goes through to sanitize your spa.

Salt is chemically known as sodium chloride (NaCl).  As saltwater enters the cell, a safe, low-voltage current passes between special rare-metal plates, producing pure chlorine (Cl) from the saline solution.  The chlorine instantly converts to hypochlorous acid (HOCl), which disinfects and oxidizes contaminants in the hot tub water.


Through this controlled process in the low-current electrolysis cell, chlorination is produced in just the right amount to sanitize the spa water.

Wait… Chlorine?

That’s right. This ‘fountain of youth’ is a chlorine factory.

Many hot tub users who appear to have an allergy or other aversion to chlorine, found no such problems after switching to a salt-based system.  The additives in packaged chlorine could be to blame.

Also, chlorine isn’t all bad. Right beside bromine, it is the most effective sanitizer. Meaning it does a great job of keeping bacteria, viruses & other harmful microbes out of your spa.

These salt systems have settings to control the conversion of salt into chlorine.  You can easily dial the sanitizer output down just enough to keep your spa clean, but not so much that it is unhealthy or unsafe.  This ability to adjust the chlorine produced is only one of the many benefits of switching to a salt system over a traditional chemical system.

Benefits of Saltwater Systems

So why switch to a salt system if it’s just chlorine? Let’s break it down:

  • Less odor
  • Eco-Friendly
  • Low maintenance
  • Smoother, softer-feeling water
  • Gentle to dyed or blonde hair
  • Reduced eye irritation
  • Soothing to skin
  • No packaged chlorine or bromine to buy and store
  • Extremely low cost to operate
  • Easily adjusted sanitizer level

Salt systems are great for hot tubs! Just because you aren’t installing a volcanic spring in your backyard; it doesn’t mean they aren’t a great way to maintain a clean, healthy spa.

Saltwater Hot Tub = Seawater?

The most common misconception with a salt water hot tub is that it is similar to ocean or sea water.  The levels of salt in these systems are way less than that found in the ocean.

seawater vs salt spa salinity levels

Salinity Levels

Ocean Water:                                 35,000 ppm

Human tears:                                   9,000 ppm

Ability to taste salt:                          5,000 ppm

Modern Salt Pools:                           3,000 ppm

Typical Salt Spa System:                2,500 ppm

At the low saline levels used by salt chlorine generators, most people cannot even taste the salt!  However, the salinity and chlorine levels should be monitored and tested on a regular basis to avoid over-chlorination which can damage equipment over time.

Salt water systems are a natural way to sanitize your hot tub or spa but should not be confused with sea water.

Types of Salt

Your choice of salts is very important.

Don’t Use:

Iodized table salt

Rock salt


These contain anti-caking agents and other additives and impurities that can foul the electrode plates of a chlorinator.

Do Use:

Refined mineral salts

Additive-free food grade salts

We love Bokek Dead Sea Mineral salts, which contain the necessary levels of sodium chloride and other beneficial minerals not found in other salts.

Benefits of Mineral Salts

The Dead Sea has many naturally occurring minerals, some found in no other sea, lake or ocean.  They nourish the skin and invigorate the circulatory system, while easing discomforts, everyday aches and pains and muscle soreness.

minerals in Dead Sea Salt

Minerals in Dead Sea Salt

Magnesium: essential for cell metabolism

Sodium ions: promote supple-feeling skin

Potassium: for muscles and the nervous system

When do I Replenish the Salt?

As the hypochlorous acid is used up, the chlorine recycles back into salt.  This economical system allows for the salt to be topped off occasionally (mostly due to water splash out). It should be replenished when the water is changed every 3-4 months.

Converting to a Salt Water Hot Tub

The Saltron Mini can be installed in about 10 minutes, without any power tools or modifications to your spa.  Just attach the main unit to your hot tub cabinet or a nearby wall with a screwdriver, drop the cell in the water and plug it in.

Before converting: We recommend following these steps to perform a proper transition from any other sanitizer.

  1. Remove your filter and use a spa system flush product to clean the interior of your plumbing from any leftover chemicals, gunk and heater scale deposits.
  2. Run pumps and jets for a few minutes after adding flush and drain away the old water.
  3. Add new water and adjust chemistry levels.

Adding Salt System:

  1. Test levels make sure you have sanitizer residual of 1-5 ppm.
  2. Measure current amount of salt in your spa.
  3. Turn on main spa pump and add the required amount and type of salt needed according to your operations manual. Spread over the surface and allow salt to dissolve for at least 20 minutes.
  4. Place the cell in the spa, preferably one foot under the water line.
  5. Plug the power supply into a GFCI protected outlet.

SpaDepot.com offers a Salt System Pro Kit which includes full size containers of mineral salts and essential spa supplies for the start-up and maintenance of your salt-based chlorine generator.

Ozone: The Saltron Mini is completely compatible with ozone, it even enhances the water quality of ozonator-equipped spas.  Maintaining properly balanced water is essential, as with any system.



Salinity/salt: 2,000 – 2,500 ppm

pH: 7.4 – 7.6

Free Chlorine: 3.0 – 4.0 ppm

Calcium Hardness: 150 – 300 ppm

High chlorine levels: acceptable level is between 3-4 ppm.  To lower the output of chlorine, you’ll want to reduce the number of hours the generator operates.  For example, if you’re running it for 10 hours, you’ll want to reduce the time to 5 hours and monitor the change.

Low chlorine levels: acceptable level is between 3-4 ppm. To adjust the output of chlorine you’ll want to increase the number of hours the generator operates.

The salinity and chlorine levels should be monitored on a regular, weekly basis to avoid over-chlorination which can damage equipment over time.




Reasons NOT to Convert

Warranty: If you are thinking of adding a saltwater system to your brand new hot tub, you may want to reconsider.  Most manufacturers state in their warranty guidelines that any damage caused by salt-based systems will not be covered and void the entire warranty.

Some new hot tubs come with installed salt systems, but at a hefty mark-up.  You are better off saving hundreds, if not thousands of dollars installing your own salt system. Before purchase, carefully read the warranty for any exclusions based on salt.

Chlorine: If you are trying to avoid chlorine, salt systems are not a good choice.  As mentioned earlier, salt systems generate chlorine through special rare-metal plates in the cell.  However, many hot tub users who think they have an allergy or other aversion to chlorine, found no such problems after switching to a salt-based system.  The additives in packaged chlorine could be to blame.

To recap…

Salt Water Advantages:

  • Extremely low cost to operate
  • Less odor
  • Eco-friendly
  • Low maintenance
  • Smoother, softer-feeling water
  • No packaged chemicals to buy and store

Salt Water Disadvantages:

  • Do not use ionized table salt, rock salt or ice-melt! These contain anti-caking agents and other additives and impurities that can foul the electrode plates of the chlorinator.
  • Regular testing of salinity and chlorine levels are required to avoid over-chlorination which can damage equipment over time.
  • If salinity levels exceed recommended amount, the only way to remove salt is by draining the water and adding fresh water.
  • Periodic cell inspection should be performed every 3 months. Inspect for scaling (white, sugar like) deposit. If scaling exists, the cell should be cleaned.
  • Do not use a saltwater spa system if you’re trying to avoid chlorine.

Salt water spas for sale are just over-priced hot tubs that dealers try to sell as one-piece units. Don’t be fooled, ANY spa can be converted to a salt water hot tub.

Have you already converted to a salt system? Share some of your tips and tricks!


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