Salt Pools: The Truth about Salt Generated Chlorine

July 21, 2016
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Given the popularity of salt chlorine generators in residential and commercial pools, it is appropriate to share some valuable information for saltwater pool owners/operators, or those considering making the switch to salt.

We spoke with two swim school owners who are considering switching from liquid chlorine to salt. Their reasoning is due to the competitive nature of the swim school business—potential customers (parents) ask them if their pool is chlorinated, because they seem to prefer their kids swim in a salt pool. Those same parents genuinely believe that salt water means there is no chlorine in the water; a belief that, while incorrect, is widespread.

Perhaps the myth that salt pools have no chlorine in them comes from the idea that you don't need to add chlorine to a salt pool. But the truth is, yes, salt pools ARE chlorine pools.

Disclosure: Orenda does not produce/sell/distribute salt, chlorine, or any other type of sanitizer. Orenda products work with any type of sanitizer available on the market today, including saltwater. That being said, the health of pool users matters to us, as well as the sanity of pool operators. This article is meant to be informative about the facts, pros and cons of salt water treatment.

Myths about Salt Pools

electrolysis, saltwater generator, salt chlorine generatorMyth: saltwater pools are "chlorine free"

False. Salt systems are actually chlorine generators, using a process called electrolysis. Electrolysis happens by sending electricity through salt water (sodium chloride, or NaCl), which interacts with the chloride ion in the salt. This creates chlorine in the water, and a very high-pH byproduct called sodium Hydroxide. The now-chlorinated water flows into the pool, and voila! You have a chlorine pool that tastes like saltwater.

You can read more on electrolysis here. To be fair, we do not know of any salt cell manufacturers foolish enough to claim their salt systems allow for a chlorine-free pool, because chlorine generation is exactly what salt generators do. This "chlorine free pool" is more of a myth that the public believes for some reason. Perhaps it's the perceptions that salt-generated chlorine is a more natural chlorine? Not sure. But it's pervasive, and false. It's actually a running joke in the pool industry.

Myth: saltwater is healthier for your skin than chlorine.

Well, again, salt pools are chlorine pools, so it depends on how this claim is worded. As we just discussed, there is chlorine in saltwater pools. So is salt water healthy for swimmers? Saltwater certainly tastes better than a traditionally chlorinated pool, and some people may get less irritation or dryness on their skin after swimming. However, this seems to be largely subjective to people’s opinions. Some people like saltwater, others hate it. The same argument could be made for natural vs. synthetic compounds, but without scientific evidence one way or another, we are in no position to make claims. It's just opinions.

We have not found any scientific evidence that salt-chlorinated pools are any healthier for people than traditionally-chlorinated pools. If you have, please send it to us.

Myth: saltwater pools have less chloramine problems.

False. Again, it’s still chlorine, and chloramines will still be created. Just like traditionally-chlorinated pools, chloramines can still be relentless and brutal in saltwater pools—particularly with regard to air quality and corrosion. Corrosion actually is worse for salt pools for at least two reasons. First and foremost, salt itself is corrosive. Go to a beach town and look around if you don't believe us. Look at the underside of vehicles in the north, where the roads get salted in the winter. Look at the rust on everything metal near the ocean. Second, saltwater conducts electricity, so if the pool is not on a common bond, corrosion is rapid.

Saltwater: Pros

After the up-front costs of installing a salt generation system, it can be very cost effective to operate. Since you don’t need to add chlorine every week (just salt), your operating budget can be relieved a bit by using a salt generator. Salt cells do use electricity, but the amount of power consumed is nothing alarming.

Another benefit is consistency. Unlike liquid chlorine or tabs administered manually, salt generators consistently generate the same amount of chlorine. This is a double-edged sword, however, as mentioned in the cons below.

If people believe a salt pool is healthier for them, a benefit can be happier customers. Salt tends to be less irritating to eyes and skin, and has a familiar taste, rather than a chemical one like traditional chlorine. This is not because there is no chlorine, as discussed earlier, but because the taste of salt overpowers the taste of everything else in the water. Perception is everything.

Saltwater: Cons

The up-front costs of installing a salt generator system can be expensive. Remember those swim school owners we mentioned earlier? Their estimate for a new commercial system is close to $50,000 (and that’s just for a swim school!). Traditional chlorination systems cost a tenth of that, or even less.

With saltwater pools, owners are in a constant battle against corrosion both in their water system (pumps, filters, heaters, metal pipes, etc.) and indoor air (HVAC system, structural steel in the building, metal deck equipment, lights, and electronics in the natatorium). This, while not entirely salt’s fault, gives saltwater a bad reputation for corrosion. In reality, salt itself is not the problem…the problem is actually an electrical one. Timothy Petsch explains:

“I have seen corrosion in many a non-salt pool, and the cause of the corrosion is the same for traditional chlorine pools, especially those treated with liquid chlorine. So what is going on here? Well, quite simply, it is an issue of lack of and/or improper bonding of metallic pool equipment.” - Timothy Petsch

Yes, it turns out that saltwater is a conductor for electricity. Improper bonding (or lack of bonding) allows for electrical current to travel through the water to get to metal. This process corrodes metal much faster than normal. Click here to read more on why corrosion in saltwater in pools is affected by electricity.

Consistent Chlorine Production

Remember the benefit of consistent chlorine production? It can also be a negative. What happens when you need more chlorine to handle your bather load? Here’s a quote from Bob Harper, writing for Pool and Spa News:

“Since the ECG produces chlorine at a fixed rate, it can be difficult to overcome the chlorine demand caused by a large amount of contaminants. Depending upon the magnitude of the demand, multiple manually-added chlorine shocks may be required to solve the problem.” -  Bob Harper

Carbonate scale

Scale deposits are prevalent in saltwater, though it is easy to confuse dried up salt for scale. The wet/dry effect looks very similar to carbonate scale.

It’s not just in pools either…just look at a dock on the ocean, or any other body of salt water. Look at the white film on boats, etc. Mineral scale in saltwater happens most commonly inside the chlorine generator itself, primarily on the metal anodes. From there, it just spreads. To be fair, scale happens in regularly chlorinated pools too—but salt systems raise the pH, (requires more acid to offset than a traditional chlorine treated pool) which allows for more scale (specifically calcium carbonate scale). With scale comes more pressure in the pipes, and more need for routine maintenance to keep the system clean and efficient.

Tips for success with saltwater

Common bond

Combating corrosion and scale from saltwater can be difficult, but it is possible. First, if you are building a new pool and planning to use salt, make sure your architect, engineers (specifically electrical engineer), general contractor and electrician know to bond everything together to common ground. This mistake is made too often because it is rarely understood. In fact, we heard about it because a leading pool dehumidification company, Desert Aire Corp., shared the information with us on a particular job.

Use a saltwater-compatible scale inhibitor

Orenda’s SC-1000 is such a product. Being compatible for saltwater is essential in a scale controlling product, due to the aggressive conditions of the cells in saltwater. SC-1000 is not only saltwater-compatible, it also contains no phosphates, so it will not contribute to a potential calcium phosphate scale buildup. Using SC-1000 will help keep your pipes clean and open, which in turn keeps water pressure normal. Zach Hansen, a technical service engineer explains:

"There are products that are generally used in pools to sequester minerals but the salt chlorine generator makes it a unique situation because of the conditions within the cell, the high chlorine levels, high pH, and heat. So homeowners and service techs need to use a product for scale that is specifically designed to withstand those aggressive conditions inside the cell.” - Zach Hansen

 

Regularly test and manage your pH, and LSI

calcium hardness on salt cell, scale formation

Hansen goes on to explain that the electrolysis process creates chlorine from sodium chloride, but it also releases sodium hydroxide (NaOH). Sodium hydroxide drives your pH level up. Additionally, the process generates more heat, which leads to more scale.

Beyond just managing the pH of your water, what really matters is the saturation of calcium in your water, as measured on the Langelier Saturation Index (LSI). Salt cells give off heat, AND create sodium hydroxide. That combination makes it hard to resist scale formation, because inside the chamber of the salt cell, the LSI is very high.

Simply run your circulation for 20-30 minutes after you shut your salt cell (and heater) off to minimize risk of scale. This will allow the cell to both cool down and flush out the sodium hydroxide.

 

Rinse regularly with fresh water

Inevitably, saltwater will splash out of the pool and drip of your patrons. Salt leaves a white residue that will harden on surfaces around your natatorium. Give these surfaces a good rinse with the hose (not buckets of pool water) to keep this residue at bay.

Bottom line, if you’re using or thinking about switching to salt water, understand the risks and how to control them.

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