Category Archives: Hot Tub Spas

How to Convert to a Saltwater Hot Tub

Hypothetically speaking, too much chlorine in a hot tub can ruin your life. It isn’t likely, mind you, but it is possible! Maybe you are visiting the parents of your fiance one winter day.

saltwater hot tub

Perhaps you go to a spa in preparation for the night. Perhaps you get a bit of hot tub water in your face and spend the night teary and red-eyed. Perhaps you get accused of being a closeted drug freak.

Perhaps the engagement gets canceled. Fret not, dear listener, as you can avoid all of this by converting to a saltwater hot tub!

Saltwater hot tubs have much less chlorine to tingle the skin and burn the eyes. Combine that with less maintenance and an overall better experience. Read on to learn everything you need to know. 

Saltwater Hot Tub Conversion Basics

Switching up your cleaning and sanitizing regiment isn’t without some effort and start-up costs. The fortunate thing is that these start-up costs lead to lower maintenance costs. 

The biggest benefit of converting a hot tub to saltwater is water quality. Softer water with fewer harsh chemical concentrations is always a laudable goal.

In fact, keeping water visually clear of debris and free of bacterial contamination has been an ages-long pursuit.

A Word on Water Quality

In the past, ancient bathing-happy civilizations did a lot of work to achieve some semblance of clean. 

The first ideas included frequent water draining and finding materials which prevented infiltrations. Marble tubs and pools look great but also serve a function in the form of non-porous stone. 

Sloped pools, which could circulate running water from higher pools into lower ones, became common. In areas of high volcanic activity, natural sulfurous springs stayed naturally bacteria free. Though sometimes this was at a cost of lingering odors.

It wasn’t until 1911 that chemical solutions were discovered that could eliminate algae and bacteria. Since then, balancing out the level of the chemicals to keep the water in top shape has vied with bather comfort.

The popularity of saltwater hot tubs comes from the relatively simple process that creates it. That, and the overall comfort level of the water.

We’ll go over the two methods of conversion: drop over and in-line.

The Drop Over Method

This method uses a device that gets put into the water and salt to interact with the device. It is a little more complicated than just plopping in a chlorinator unit, but not by much. 

We’ll go over the gear you need first. Then we’ll explain the process of installation for the final conversion.


Saltwater, coupled with a chlorinator cell, are the core components. Depending on the tub, you will need to opt for a more powerful chlorinator cell.

You will also need to run the tub for different time cycles, depending on volume, the frequency of use, and circulation cycle. 

All of these options need a dedicated GFCI outlet to attach the power supply which then connects to the internal tub unit. 

A cell attached to the inside of the tub provides service for the largest tubs. For a smaller tub, you can use a hanging or floating unit. 

The chlorinator generates chlorine. This might sound like it does the same job as the chlorine you would mix and add or disperse through a controlled delivery. Chemically there are some differences which we’ll explain later on.


Once you have the chlorinator chosen and ready to install, you still need to address your initial water conditions. For a painless saltwater hot tub conversion, you want to start with balanced and sterile water. 

You may find it best to convert your spa to saltwater during a routine drain and refill. This allows you to set salt levels with ease. 

Recommendations from manufacturers include a balanced water level and a lack of initial algae. Removing all particles, such as accumulated sand or dirt, from the system will give the best performance. 

Starting with less than pristine conditions won’t likely lead to failure. It can cause enough performance hinderance to be an issue. If you feel your hot tub condition is questionable, it is better to do more upfront work on cleaning before a conversion than a premature drain and fill.

You want to have your sanitizer levels down to 1 to 3 ppm (parts per million).

Then you add salt. The amount recommended will be listed in the materials for the chlorinator cell. Typically, you will be looking at 3-4,000 ppm.

Too much salt will clog the chlorinator and prevent it from doing its job. Too little and it won’t produce enough chlorine to clean properly. 

The salt you will need doesn’t have to be a specific brand but it does need to be purer than table salt. Iodine in table salt will create problems with the catalytic processes of the chlorinator. 

In-Line Conversion

The gear and conversion information stay the same from the drop over to the in-line methods. The difference for an in-line unit is that it is installed inside other plumbing.

This gives you a seamless experience for the saltwater hot tub. The installation, however, is more work-intensive. As you would expect, this requires draining of the hot tub to make modifications within the plumbing. 

In-line units require you to have 3/4-inch tubing and a constant circulation system.

In-line units that suffer some type of defect will also require the same effort to fix and replace. For this reason, in-line units are more reliable and less prone to calcium build-ups than their drop over cousins.

The one-time effort to install an in-line unit translates into even less time performing maintenance. This is cumulative over their drop over counterparts.

A Note on the Science

You might be questioning how much salt is in saltwater. After all, the ocean is saltwater and soaking in that dries out skin rapidly. 

The concentration of salt in large saltwater bodies differs. The ocean contains 35 ppt (parts per thousand). Converted to the ppm you’re used to that is 35000 ppm and your spa is 3-4,000 ppm. 

That is roughly the same ratio of difference between an ocean and the Dead Sea. The Dead Sea, as the world’s most saline body of water, is 342 ppt. 

The difference between the chlorine being produced by the saltwater and the chlorinator is also different. 

Let’s start with an exploration of the industrial strength chlorine used in the majority of swimming pools and hot tubs. This ‘pool chlorine’ is usually the chemical compound calcium hypochlorite. 

The chlorine produced by the chlorinator from the saltwater reaction is chlorine gas. This then mixes with the water to become hypochlorous acid.

The chlorinator cell plates, titanium with a ruthenium coating, do the heavy work.

These plates, when stimulated with electrons, perform a process of electrolysis. This catalytically converts the sodium chloride of salt into sodium and chlorine gas. In chemistry notation that is NaCl becomes Na and Cl2. 

So we have two chlorines: the industrial grade and the saltwater-derived. The chemical makeup of these two compounds produces different effects.

Hypochlorous acid is an acid, and as such, needs alkaline water to maintain a neutral Ph. That is why you test water for Ph alkalinity or stability to prevent the water from burning, especially soft membranes like the eyes or nose. 

Calcium hypochlorite has a more acidic rating on the Ph scale and needs more alkalinity to balance out.

Now for the thing you most wanted to know about, that chlorine smell. Hypochlorous acid doesn’t lead to that smell for two different reasons.

The first is the even distribution leaves less chemical to further react with organic pollutants, algae, and pee. The second is that bonding with uric acid (the biggest component of note inside pee) creates chloramines.

The nasty byproducts formed by these interactions are nitrogen trichloride and cyanogen chloride. Both of these chemical compounds can cause a lot of damage to humans in relatively low concentrations. 

Nitrogen trichloride can affect breathing. This is the main contributor to asthma problems for frequent child swimmers. Irritation and inflammation in the lungs lead to long-term damage.

Cyanogen chloride is volatile and, at high levels, a carcinogen. It is also what produces that strong ‘chlorine smell’. This heavy smell also irritates breathing channels and mucous membranes. 

Yes, a hefty whiff of chlorine indicates an unbalance of either chemicals, the presence of urine, or both.

Finally, the reason your skin doesn’t dry out as much in a saltwater hot tub is that the salt levels are actually close to the ones inside the body. This means that no osmosis needs to occur. Your skin and water share the environment without pulling form each other.

While your skin won’t dry out in a proper saline mixture, it also doesn’t get pruney as quickly. So you can soak longer worry free.


It is still ideal to carry out a maintenance routine. We’ve laid out the best care for a hot tub here. You will only need to change a few techniques for the saltwater components.

You always want to perform routine maintenance to keep your hot tub in peak condition. The timing of your maintenance and its complexity is reduced by a saltwater conversion. 

Before, you had to check the chlorine level (in the form of calcium hypochlorite) and monitor PH values. Now, you check for calcium buildup on the chlorinator and check the salt level.

The tests for these take mere minutes to perform. Salt test strips have a fair degree of accuracy but drop tests are more accurate. Either is sufficient for keeping within the 3 – 4,000 ppm (or recommended by chlorinator manufacturer). 

Depending on the system, you won’t even need to test for salt levels, as the system for in-line and some drop over chlorinators warn when levels fall too low.

You will need to add salt only occasionally as the systems recirculate the majority of the salt. Ph and other balance tests will still need to be done, but less often. 

Salt won’t cause a problem or any build up inside your pump or heating devices

Don’t worry about the salt eating away at anything, either. The process of oxidation which creates rust happens with the influence of sodium chloride. The salt in your hot tub will be separated as either sodium or hypochlorous acid at any given time.

This leaves only traces of the combined element to accelerate corrosion.

If the chemistry balance gets out of control, usually due to a lack of salt or calcification of the chlorinator, you will need to shock the water. 

Shock treatments use high levels of calcium hypochlorite and take a while to filter back out. Yes, the old-school version of chlorine is more powerful as it can rapidly be adjusted in concentration. Most of the time you need strong enough, and that is what a saltwater conversion provides.


Kicking back and having a relaxing soak makes for the ideal hot tub experience. You know that there is a bit of work to get to that end goal but once your there, it’s heaven.

The experience of a saltwater hot tub is even better. The water is better, as saltwater systems provide many of the same benefits as a water softener to demineralize the water. It also provides some important health benefits

First, the lack of stronger chemicals –and their associated fumes– make saltwater spas better for asthma. You also face fewer allergy complications. 

You can rest easy without that strong chlorination smell building up, thanks to the lack of chloramines.

Saltwater and the chlorine made from the conversion within the chlorinator won’t bleach out clothing or affect hair color.

This lack of bleaching effect also serves to protect the surfaces around your hot tub. Especially if you have a hardwood or decorative deck around a spa.

Little change will occur to tile or marble areas.

Take a Soak

The one-time setup cost and the lower month-to-month cleaning and care costs will add up. You’ll enjoy more soak time for less effort and with overall better health benefits from a saltwater hot tub. 

There is a lot to know about hot tub care, selection, and maintenance. We provide as much information as we can.

Looking get started or in the market for a new tub? Check out our review of the newest tubs of the year.