Saltwater Pool Corrosion? Fact Versus Fiction

Introduction: Clearing the Waters on the Myths of Saltwater Pool Corrosion

As a pool owner or potential owner, you'll face a multitude of decisions, one of the most critical being figuring out the best way to maintain your pool with minimal effort and expense. Over the last thirty years or so, saltwater pools gained popularity due to their ease of use, improved water quality, and cost savings. Eventually, salt pools (pools which use a salt chlorine generator) have become the standard for pool care, with over 75% of new pools in the US being equipped with saltwater systems (according to P.K. Data Inc.). However, a cloud of concern often shadows the clear advantages of using a salt chlorine generator, as potential owners grapple with the poor information or misunderstandings, often regarding the concern of “salt water pool corrosion”. At the start, it's important to understand that “salt pools” and salt chlorine generators have been used safely on millions of pools for decades, and are safe to use on virtually all pool types.

This comprehensive article sets out to demystify saltwater pools, explain what swimming pool corrosion is, and debunk myths with reliable, science-based information, as well as to provide information on how to treat your pool to prevent corrosion (because whether it uses a salt chlorine generator or conventional chlorination corrosion can happen in pools). Pool corrosion vulnerabilities are not limited to saltwater pool owners, nor is pool corrosion primarily due to the use of saltwater pools. This is the definitive guide for anyone looking for information on the truth of salt pool corrosion, which of course begins with understanding what corrosion is.

Understanding the Science: Saltwater Pools and Salt Chlorinators

A misconception that often arises about Saltwater pools is that they have salty ocean-like water so that they can operate without any chlorine, and are thus more prone to corrosion. Contrary to this belief, saltwater pools use a device known as a salt chlorinator or “electronic chlorine generator”. This device continually converts a very low level of salt in the water into chlorine, ensuring your pool remains clean, clear, and safe from harmful bacteria and algae.

The salinity level in saltwater pools is in reality far, far less than that in seawater. It’s not even really comparable. While seawater has about 35,000 ppm (parts per million) of salt, a swimming pool using a chlorine generator only needs about 3,000 - 3,500 ppm, which is much closer to freshwater in comparison. To be precise, the salinity in the pool is just slightly above the technical range of what freshwater is considered at 1,000 ppm or less).. This salinity level for the pool is even less than that of human tears (9,000 ppm) and far under what the human tongue can typically even taste (about 4,500 ppm), which is why “saltwater pools” are not in fact “salty” or like the ocean in any way.

So the presence of the chlorine generator and this low level of salt in the water is the difference between a “salt pool” and a “traditional pool”. When an inground pool or permanently-installed aboveground pool is installed & maintained properly, and built with pool-grade materials, they are designed to resist the highly caustic effect of chlorine itself. In reality, the level of salinity in a “salt pool” is so low that it is not known to have a significant effect on corrosion, especially in comparison to what is at play with the balance of other pool chemicals..

Corrosion in Pools: Why does it happen?

If not treated right, corrosion can happen in any pool - but what does that specifically mean? Corrosion is defined as a process that leads to the gradual destruction of materials through chemical reactions with their environment. This is a concern for all pool owners, regardless of the type of pool they own. Concerns about the issue are valid, because it can be quite a process to deal with pool corrosion. Since pool corrosion vulnerabilities are not limited to saltwater pool owners, nor is pool corrosion primarily due to the use of saltwater pool chlorine generators, this is important information that can benefit anyone that owns a pool.

Several factors can contribute to corrosion, including chemical balance, the presence of different types of metals, water temperature, the presence of oxygen, and the bonding/grounding of the pool and pool equipment. These factors can cause a range of types of corrosion when not cared for properly, which can impact various components of the pool, including metals found on pool lights, rails, pool pump, pool filter, skimmers, and even the walls, leading to their gradual degradation.

We’ll go over many common types and causes of pool corrosion, and how to treat your pool so as to prevent it.

Corrosion from High Chlorine Levels In The Pool

This may be the #1 thing to avoid to prevent pool corrosion. Chlorine is a highly reactive oxidizer. Chlorine is caustic. A report by D.S. Novak based on a Case Western Reserve University’s Dept. of Metallurgy and Materials Science study showed that high chlorine levels were the primary cause of corrosion. Within 8 days, enough corrosion can occur in grade-304 stainless steel so as to cause the material to fail when exposed to a chlorine level of 20 ppm . As mentioned above, pools that are built to last in a chlorinated environment essentially shrug at the very low level of salt used by a salt chlorine generator. But however you are chlorinating your water, avoid unnecessarily high chlorine levels otherwise you might walk yourself into a world of pool trouble. This means aim to keep your pool consistently at 1-3 ppm free chlorine.

One of the primary ways pools commonly get very high chlorine levels is because they have to get “shocked” (super-chlorinated) due to inconsistent, insufficient, and improper chlorination. If you don’t maintain just the right level of chlorine and that level dips, microorganisms like algae can start growing and chloramines form in the water, which both can require treatment by adding enough pool shock to greatly raise the chlorine level. This is actually an area where salt pools can actually reduce the potential for corrosion: since salt chlorine generators provide consistent and reliable chlorination by working at a precisely set rate every day when the pool system runs, this typically eliminates the need to regularly shock the pool!

TIP: Since chlorine is so caustic, one essential practice for any pool owner is to regularly hose down the pool environment including covers, rails, furniture, patio/deck, etc… Otherwise you’re basically accumulating a layer of chlorine on top of everything that has pool water evaporating on it.

Corrosion from Chloramines and Chlorine Fumes

As mentioned, chloramines form in the pool water when there is not enough chlorine in the water to fully oxidize all of the impurities present. Chlorine combines with these impurities to produce a nasty substance that is responsible for many of the caustic qualities that people think of when it comes to swimming pools: red eyes, itchy skin, bleached hair and swimsuits, the “chlorine smell”, and more. But furthermore, it's been shown that chloramines can also cause corrosion on metal parts within a pool enclosure. Similarly, storing chlorine is itself a hazard for corrosion. The fumes and vapors that are emitted can accumulate where large amounts of chlorine is stored, and can cause a significant effect on metals and other materials in the surrounding environment. This is another area where a salt pool can reduce the potential for corrosion, since not only do salt chlorine generators eliminate chloramines, they also eliminate the need to regularly buy, store, and handle chlorine.

Corrosion from Improper Bonding

This type of pool corrosion can sneak up on you and may happen over time without you realizing it.

Bonding is a special type of grounding, where all metallic pool components are connected together by a dedicated copper wire and this loop is connected to a local grounding source. In fact, as of 2008 the National Electrical Code (NEC) has mandated that pool water itself shall be electrically bonded, not just the metals in the pool system. This is done to protect swimmers from electrical hazards, but this is also done to prevent what are called “stray currents”. Stray current can form naturally or be caused by the pool system or other reasons like galvanic action, where the presence of different types of metals induces the flow of electrons. In an improperly bonded pool, these stray currents can get out of control and “seek” the easiest path to conduct their charge through. In this situation stray current can cause corrosion and degradation of whatever material this flow of electrons occurs through.

It could be that when the pool is built the pool was not properly bonded, or not properly terminated in order to provide sufficient grounding. However, it is more likely that a bonding issue crops up later down the road, like when new equipment is installed or swapped out, and the bonding loop is no longer connected to all items. Another common example of this problem occurring is when pool lights are switched out for plastic LED or nicheless LED lights; unless other changes to the bonding are made at the same time this can inadvertently remove the pool’s water bond!

Whether you are chlorinating your pool conventionally or using a chlorine generator, proper bonding is critical. It can be worth it to take the time and trace your pool bonding from component to component, ensuring that it is all continuously connected to an independent local bonding rod which is able to provide a proper grounding source.

If some portions of the bonding are buried or inaccessible, which is possible, or if you are unsure, or if you are in fact seeing corrosion or issues with stray current, a simple possible solution is the addition of an inline water bond & zinc anode. This component is usually easily installed and can protect the whole pool by providing sufficient water bonding and a “sacrificial” path for any stray current to be directed through. This can be a relatively inexpensive way to provide an additional layer of protective bonding for your pool. Be sure to consult with a qualified individual whenever you are dealing with anything related to electricity.

Corrosion from Acidic Water or Mishandling Chemicals

Acid is inherently corrosive, and adding acid to swimming pools is a common part of maintaining the pool’s pH. The pH of the swimming pool is a critical component of the water chemistry balance. While many pools tend to have their pool water drift towards a more alkaline high pH, the use of some pool surface types, the use of some chlorine chemical products, as well as things like decomposing organic matter in the pool can encourage a lower pH in the water. If factors push the pool water to a more acidic low pH, the acidity of the water can begin to be more and more corrosive. Additionally, significant corrosion can occur when acid is mishandled, spilled, or not added to the pool properly. Inaccurate chemical test readings as well as mismeasuring the amount of acid to be added to the pool can also cause too much acid to be added to the pool. These situations can expose things in and around the pool (as well as swimmers) to highly corrosive and dangerous levels of acidity.

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Corrosion from Too Little Chlorine Stabilizer

Chlorine stabilizer (or CYA) is an important part of the water chemistry and ensures that the sun’s ultraviolet light does not cause chlorine to be quickly depleted from the water. Chlorine stabilizer also slows down the corrosivity of chlorine, even at levels as low as 10 to 20 ppm. Keeping a minimal level of chlorine stabilizer in the water is then doubly beneficial for both chlorine effectiveness as well as inhibiting corrosion. Recent research shows that chlorine stabilizer should be kept at no more than about 13.3x the level of free chlorine in the pool (ex: 40 ppm chlorine stabilizer and 3 ppm free chlorine)

Corrosion of Improper Materials

Let’s take a look at common examples of pool corrosion that shouldn’t even occur in the first place! These corrosion circumstances should be prevented by applying forehand knowledge of which materials are designed for use in the chlorinated environment of swimming pools.

Uncoated regular steel or cast iron are metals that might be mistakenly used in pool-side furniture or decorations. Items made out of these metals would be highly susceptible to corrosion due to the pool water and chlorine. Ensure that all metal in or near the pool is pool-grade, such as stainless steel or aluminum. Don’t put decorative cast iron near your swimming pool. If steel is present, ensure that it is properly coated and that the coating is free of damage.

Though it might be commonly used in inexpensive above ground pools, galvanized steel should be avoided in the pool environment. Much research shows that it is a matter of when not if it will corrode when chlorinated water is present. If a pool is designed to last many years, it is going to use a more resilient and non-reactive material such as high-grade metals or resin.

These next examples are more properly described as degradation than corrosion, but are still helpful to know. Ensure that the following materials are marine-grade or intended for use in an environment of chlorinated pool water. Use of proper PVC components are used such as Type 1 Grade 1 Schedule 40 PVC pipe, or high temperature Schedule 80 CPVC pipe; improper PVC could get brittle and break down in chlorinated water. Use tile and grout designed for use in swimming pools, otherwise it may discolor or even break down. If you replace any seals or o-rings, make sure you don’t substitute an improper part made of a type of rubber that’s not intended for contact with chlorinated water. If wood decking is present, make sure a proper type of wood is used to withstand wet environments and that the wood is treated and sealed so that it isn’t broken down by chlorinated water.

do salt water pools cause corrosion?

Concerns about corrosion in swimming pools are real - you can see from the above examples that there are many common ways that corrosion can occur in virtually any pool, and in each example it’s clear that cause of such corrosion is not the low level of salinity that is present in the pool water so the chlorine generator can operate. Often when pool owners are seeking information on how to understand and treat salt water corrosion claims, they may be shown examples of pool corrosion where the real cause is commonly chlorine itself, improper bonding, or any of the other common examples that can occur on virtually any swimming pool. As discussed above, the low salinity level in pools that use salt chlorine generators is not known to have a significant effect on corrosion. Below are more examples of damage to a swimming pool that can happen that can get wrongly blamed on the use of a chlorine generator on a pool.

Corrosion vs. Erosion: Understanding Pool Damage

Often, other types of pool damage can actually be confusing the terms corrosion and erosion. Despite their similarities, these two processes are distinct and can contribute to the degradation of the pool in different ways. While corrosion refers to a chemical process that results in the gradual destruction of materials like metal, erosion refers to a physical process where the surfaces are worn down. This can be due to water flow or mechanical action, as well as chemical erosion, which is the dissolution due to acidity. This type of effect could lead to rough pool surfaces or even damage to the pool plaster.

What is the cause of erosion damage? This is due to an imbalance of the water chemistry that has to do with the acidity of the water, the lack of calcium in the water, and its ability to dissolve materials and pull material into solution. This imbalance of the water is called a low Saturation Index (or low LSI). When the pool’s LSI is low, it means that the water is able to eat away at mineral substances and etch them, so this can cause damage to plaster, concrete, even some natural stone. In the right conditions, low LSI can also cause calcium crystals to grow on plaster and concrete, which can be destructive and leach out minerals and harm the pool surface.

Damage to the pool surface is one area where confusion and misunderstanding can be used to scare pool owners unfortunately. The low salinity in a salt pool is not harmful, and using a salt chlorine generator is safe for virtually all pool surfaces including gunite and concrete pools, plaster pools, PebbleTec(R) pools, tile and grout, stone, and any other mineral-based pool surface. (It's safe for vinyl-liner and fiberglass pools as well - virtually all common pool types.) In fact, it's helpful to remember that we build bridges and other structures using these materials which are constantly in ocean-strength saltwater which is about 10x the salinity or more.

Thankfully, for every one example of a person dealing with confusion on the issue, you can find more people who can attest to the safety and reliability of a salt water pool.

The Role of Salt Chlorinators: An Ally for Pool Owners

Salt chlorinators are just electronic chlorine generators that allow for automatic pool sanitization, a role that is crucial for the functioning of any swimming pool. They convert a very low level of salt into chlorine, ensuring your pool remains free of harmful microorganisms. However, because “saltwater” is mentioned, it makes people think of the ocean, and some pool owners may mistakenly associate these devices with increased pool corrosion.

It's vital to understand that salt chlorinators are time-tested and safe for pool surfaces and equipment, and have become significantly more popular and more widespread than conventional chlorination for new pools, as over 7 out of 10 new pool in the US were equipped with salt systems as of 2007 (according to P.K. Data Inc.). Rather, corrosion often results from improper maintenance of water chemistry or improper pool setup, whether the chlorine in the pool is generated by a salt chlorinator or manually added. As a result, understanding the correct use and routine maintenance of salt chlorinators can play a significant role in preventing corrosion in saltwater pools.

Materials and Safety Considerations: A Guide for Pool Owners

Safety should always be a priority when it comes to pool ownership. Alongside this, the choice of materials used in the construction of your pool is equally important. Certain materials, such as the galvanized steel often used for temporary short-lived seasonal pools, can be more prone to corrosion. However, for permanent pools designed for high-quality and durability, encountering significant issues with corrosion is not common since pool-grade materials are used which are designed to withstand the corrosive nature of chlorine (provided of course the pool's water chemistry is appropriately maintained).

Implementing protective coatings (such as sealing porous surfaces) and verifying proper bonding (and even utilizing sacrificial anodes to ensure a proper water bond) can offer the needed protection against natural corrosion and chemical erosion that swimming pools can experience. This can go a long way towards enhancing the longevity of your pool, ensuring you can enjoy it for many years to come.

If considering an above ground pool, invest if possible in a more permanent swimming solution made with high quality components like resin, aluminum, and stainless steel, one that’s built to last year in and year out, and you’ll avoid the worry about pool corrosion.

Water Testing: A Crucial Task to Prevent Pool Corrosion

Don’t wait until you're wondering how to treat corrosion, whether on a salt pool or conventional pool. As noted above, the most common pool corrosion occurs due to high chlorine levels, as well as acidic pH issues and poor pool bonding. The crucial task actually begins with preventing it from occurring in the first place. Consistently testing the water’s chemistry is a fundamental task for every proactive pool owner. Regular monitoring of parameters such as pH, total alkalinity, calcium hardness, LSI, and especially chlorine levels plays a significant role in preventing pool corrosion, regardless of whether your pool is “saltwater”, or traditional chlorine based.

Regular water testing allows you to detect these imbalances early and make necessary adjustments to prevent potential damage. Have a testing kit on hand always, as well as the necessary chemicals for adjusting your pool chemistry.

There’s no need to treat pool corrosion or clean pool corrosion if it never occurs in the first place. Furthermore, treating corrosion is not even possible in many cases as corrosion represents the actual loss of physical material. If caught early and occurring at minor levels, you may be able to remove small amounts of corrosion.

Cleaning Pool Corrosion: A Guide for Saltwater and Chlorine Pools

No matter what type of pool you own, being able to address signs of corrosion is an integral part of your pool maintenance routine. Regular inspections can help identify problematic areas early and address them before they escalate into a major issue, saving you time and money in the long run.

For minor pool corrosion cleaning jobs, specialty cleaning chemicals and tools can prove to be effective. Specific brushes and abrasives, combined with pH-neutral cleaners, can remove rust and other signs of corrosion. However, remember that the key to cleaning pool corrosion lies in prevention. Maintaining balanced water chemistry, avoiding high chlorine levels, and verifying proper pool bonding (or implementing protective measures, such as sacrificial anodes), are going to address the primary causes of pool corrosion. After all, if it never occurs in the first place, then there’s no reason to clean pool corrosion. To say it another way, if corrosion is happening, the root cause needs to be addressed (aside from faulty materials of course).

In more severe cases of treating pool corrosion for your pool, it may be necessary to seek professional help. A professional can accurately assess the situation and recommend effective solutions. This could involve replacing parts, repairing damages, or suggesting alterations to your pool maintenance routines.

Material Choices and Protective Measures: Navigating Your Way to Corrosion-free Pools

One of the key aspects of treating corrosion in pools, saltwater or otherwise, lies in making informed material choices. This begins right from the construction phase. For instance, using pool fittings made from noble metals like stainless steel, or at least, materials that have been treated to resist corrosion, can prevent issues later on.

Anodized aluminum, which has been treated to form a protective oxide layer, resin components, PVC parts, or plastic fittings, can also be viable alternatives for corrosion-prone areas. Tile and grout used need to be pool-grade. Any porous materials like wood and stone need to be sealed when in any swimming pool environment.

Pool owners can also consider additional protective measures. Sometimes in the real world, prevention isn’t fully possible. Sacrificial anodes (also known as zinc anodes) can be used to protect pool hardware from corrosion. The idea behind sacrificial anodes is that they will corrode before other metals in the pool, effectively sacrificing themselves to protect the more valuable parts of your pool. This addresses one of the primary factors in pool corrosion, which is proper bonding, and provides a way to deal with corrosive forces in the swimming pool. While these are not required as a matter of course when installing an electronic chlorine generator when the pool is already properly bonded, it is easy to also add an anode during the installation process and raises your pool’s level of bonding-related protection.

Paying Attention to the Pool Surrounding: A Comprehensive Approach to Corrosion Prevention

When discussing pool corrosion, it's essential to also pay attention to the area surrounding your pool. Sprinklers, for instance, can cause corrosion if they are spraying water onto the pool deck and pool equipment and keeping things continually wet. (However, you should in fact rinse off your pool environment regularly after use to make sure that chlorinated water doesn’t remain, evaporate, and build up over time). Similarly, if you live adjacent to the coast, sea spray can introduce significant amounts of salt into the environment (unlike the low level of salinity required by a chlorine generator), potentially exacerbating corrosion.

Hose off the pool environment regularly. Consider adjusting your sprinkler systems to prevent water from reaching the pool and equipment and make sure it isn’t too frequent so as to keep things saturated. Ensuring the pool area is free from debris and regularly cleaning the pool deck can also go a long way in preventing corrosion, as rotting organic material can create acidic residue.

Conclusion: Proactive Steps to Address Pool Corrosion

The misconception that saltwater pools are inherently more corrosive than traditional chlorine pools can be concerning for potential pool owners, making them worry if they will have to face the prospect of having to treat saltwater corrosion. However, “saltwater pools” have a long history of safe use, and with a thorough understanding of the nature of corrosion and proactive measures to treat the ways that it can happen on virtually any swimming pool, you can keep your pool in prime condition, regardless of its type.

Proper pool setup, regular maintenance, informed material choices, and a keen focus on water chemistry are essential to prolonging your pool's lifespan and ensuring a safe, enjoyable swimming experience for all. As a pool owner, remember that knowledge is power, and that unfortunately there are lots of misunderstandings and myths when it comes to swimming pools. The more you understand about your pool and its needs, the better equipped you'll be to maximize its benefits and circumvent potential pitfalls.

Don't let concerns about corrosion discourage you from choosing a saltwater pool. There are millions of pool owners who have switched from the process of having to manually buy and add conventional chlorine chemicals to the modern process of automatically generating chlorine on demand. Armed with the right information and tools, you can keep your pool a place of relaxation and fun for years to come. This comprehensive guide should serve as your starting point in your journey to understanding and managing saltwater pool corrosion. With this knowledge, you can fully enjoy the benefits of owning a saltwater pool, with no undue worries about corrosion.

Should you have any questions or anything you wish to clear up on the topic of treating saltwater pool corrosion or dispelling the myths that saltwater pools are somehow more prone to pool corrosion, do not hesitate to contact us at Discount Salt Pool.

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Jon Sargeant

Date 3/7/2024

Hi , just read your article on salt water chlorinators and corrosion. Great article. I have a pool with a salt water chlorinator and am thinking of installing a titanium heat pump. Everything I have read about titanium corrosion indicates that in an oxidising enviroment / chlorine/chlorides there is no issue with corrosion. Yet all manufacturers recommend that the chlorinator be installed after the heat pump, not before it. To install the chlorinator after the heat pump in my system requires a complete replumbing job. To install the heat pump after the chlorinator is a very simple operation. Am I missing something here? Are heat pumps manufactured with a poor titanium alloy that can't handle chlorine from chlorinators ??

DSP Staff

Date 3/12/2024

Chlorinators and Chlorine Generators are typically directed to go after the heater / heat pump because the immediate output of chlorine within the plumbing is a much higher concentration than the level of residual chlorine generally found within the swimming pool water.

Charles Adams

Date 5/13/2024

I've been told not to use these on my above ground pool. Would love to though. What do I need to know?

DSP Staff

Date 5/13/2024

You might appreciate this guide:

The basic facts are that the salinity level required for an electronic chlorine generator (~3500ppm, compared to the ocean at ~35,000 ppm and freshwater at up to 1000ppm) is not a significant level of salt. High chlorine levels are the #1 driver of rusting in virtually any pool according the research in these articles.

Where the salinity in the pool water can come into play is if there is already a bonding issue at play in the pool. If any pool is not properly bonded, there can be a trickle of stray "galvanic" current between different metals present, and this current can slowly cause oxidation (rust, if you're talking about steel). If the pool has an issue with galvanic current, it could occur faster due to the slightly higher conductivity of the water. For above ground pools, inexpensive low-grade materials may also be used so for sure check with the pool manufacturer.

If there is any concern about improper pool bonding, inline "zinc anodes" and easily and inexpensively be added to serve as a water bond, as mentioned in other comments.

Please feel free to contact us with any questions, we're happy to help. Using an electronic chlorine generator is pretty much the standard at this point, so don't let a lack of information stop you from looking into it.

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