Chlorine pools were the norm until the 1980s when salt water pool technology first came to North America in earnest. But the history of salt water pool chlorination actually goes back further to the 1970s and to another continent.
The first salt water pool chlorination system was invented in New Zealand in 1972 by Cascade Pools and was called the Aquatech IG450 Salt Chlorinator. It was designed for a pool up to 10,000 gallons and used a 12 volt DC four-plate stainless steel electrode to produce sodium hypochlorite to sanitize the water.
The first salt water pool chlorination system design
The Aquatech IG450 Salt Chlorinator was the name of the first salt water pool chlorination system designed in New Zealand by Cacsade Pools. The IG450 model number represented what the chlorinator was designed for:
IG: Stands for Inground Pool which is the pool type that the chlorinator was designed to work with.
450: Represents the 45,000 liter (11,889 gallons) size of the pool that it was capable of serving. Around that time, a 10,000 gallon pool was the average capacity for inground pools.
The IG450 produced liquid chlorine by converting regular salt to sodium hypochlorite for sanitation by using a 12 volt DC four-plate stainless-steel mesh electrode which today we’d refer to as a salt cell. When the salt water passed through the electrode, it was electrified using a process called electrolysis which is the same principle used in modern salt water chlorinators.
The second generation IG450P salt water chlorinator
The next generation chlorinator from Cascade was designed to improve upon the initial design and was called the IG450P where the letter P denoted the use of a platinum electro-plated stainless steel electrode which increased the lifespan by twofold.
Whereas the first generation IG450 model used stainless steel plates, it didn’t last very long and deteriorated within several years which required the electrode to be replaced more frequently that was desired. The destructive nature of salt water when it comes into contact with metal is something that would become more prominent as salt water pool technology developed.
The third generation IG450A salt water chlorinator
The third and final salt water chlorinator built by Cascade Pools was called the IG450A where the letter A represented the word acid or hydrochloric acid more specifically.
Around 1994, the company had finally achieved a solid understanding of pool chemistry as it related to salt water pools. They had discovered what salt water pool owners even today realize: A high pH destroys chlorine and by the time the pH level hits 8.0 it becomes almost impossible to sanitize a pool. Up until this point in time, the two previous chlorinator designs of both the IG450 and IG450P didn’t account for the high pH that resulted.
By manually adding hydrochloric acid to the water, one could reduce the pH level to a more appropriate one. So the IG450A was designed to utilize a 40 liter (11 gallon) drum of hydrochloric acid that would be added to the pool water to regulate pH.
Given the dangers of storing large amounts of hydrochloric acid around the home and having a container of it near the pool in the vicinity of children, Cascade Pools eventually abandoned the idea of salt water pool chlorinators moving forward. This occurred for a few reasons.
Other salt water chlorination problems
By the time the third generation IG450A was abandoned in 1994, the unit cost for each chlorinator cost $2,800 plus the cost of the hydrochloric acid, a total cost that would be considered high even by current standards.
While testing and designing salt water pool chlorination systems, Cascade Pools noted other problems with the use of salt water pool technology, including at least one that exists today even with modern chlorinators.
Other than the problem with the high pH that Cascade Pools tried to counter with the automatic addition of hydrochloric acid, they also noted the damage that the salt water caused to metal around the pool such as the ladder and other equipment. This remains a concern to salt water pool owners to this day.
Cascade also noted what they referred to as voltage leakage or stray voltage which constituted a potentially major hazard: The lack of grounding in the chlorinator system often caused damage to the pool pump and heater and also a constituted an electrical risk if a swimmer touched the metal pool ladder for example while still in the water, something the company was able to address.
They also noted the effect of calcium and other mineral deposits that would develop on the electrode (salt cell) over time. The deposits damaged the electrode unless cleaned and reduced its ability to produce enough chlorine to properly sanitize the pool. It also led to a premature need to replace the cell, something salt water pool owners experience to this day.
It is worth mentioning that Cascade Pools was not only ahead of its time with its salt water chlorination technology, but also how they did account for the fact that mineral build up on the electrode was a problem to be dealt with.
What is reverse polarity?
Reverse polarity is a feature that is becoming standard on new salt water chlorinator systems as a matter of course but amazingly, a similar feature was included in early chlorinator models manufactured by Cascade.
With a salt water pool, minerals like calcium attach themselves to the metal plates inside the salt cell. Over time the plates become clogged with these minerals which can inhibit their ability to produce chlorine for your pool and may eventually result in the cell failing and needing to be replaced sooner than you’d like.
Traditionally, salt water pool owners had to shut their pool pump off, unscrew the salt cell and soak it in a bath of water and chemicals, often muriatic acid. It’s a time-consuming job and involves chemical usage too. Many older style and less expensive salt water chlorinator systems still require pool owners to do this.
But newer systems have a reverse polarity cleaning feature which temporarily reverses the electrical current inside the salt cell to remove the minerals and deposits automatically, eliminating the manual cleaning.
Reverse polarity was initially included standard
Back in 1974, Cascade came up with a similar feature called polarity switching that alternated electric currents automatically while the pool pump was running to remove the minerals. This feature alternated the current every minute or so and they marketed the chlorinator as self-cleaning.
They found that the feature didn’t work as well as desired however. Calcium and other mineral build up tended to occur on the salt cell anyways. Calcium content was made worse with the use of Cal-Hypo (calcium hypochlorite) crystals as it meant that pool owners were adding a calcium-rich product with a high pH to the water.
So by adding Cal-Hypo to pool water, you’re literally adding one of the minerals (calcium) that attaches itself to the salt cell and further raising the pH of your pool water which is the major reason why calcium builds up on the cell in the first place.
Given the first generation nature of salt water chlorination design at this time, the reverse polarity cleaning feature didn’t work as planned and it was found that mineral build up occurred regardless which necessitated the manual washing of the cell anyways.
Check out my article called What Is Reverse Polarity In A Salt Water Pool Chlorinator to learn more about this convenient self-cleaning function that only now is being introduced automatically on salt water chlorinators.
Why the initial reverse polarity feature failed
Initial salt water chlorinator salt cell design included a four-plate stainless steel electrode which was found to deteriorate and last no more than 2 – 3 years at best. The next generation cell switched the electrode to a platinum electro-plated stainless steel design that was found to last 2 – 3 times as long but also cost twice as much to replace.
The reverse polarity feature also worked continuously while the pool pump ran meaning that reverse polarity was working the entire time on and off every minute or two.
By comparison, modern salt cells are sold with a multi-plate (10 or more) design consisting of titanium electrode plates coated with iridium, ruthenium or another substance used as a barrier coating for extended cell life. The use of titanium rather than stainless steel is an improvement that also leads to better cell performance and a longer lifespan.
Current reverse polarity cleaning features don’t cycle on and off every minute though: Modern chlorinators use a set time to operate the reverse polarity feature that runs continuously unless it is done. So it’s a dedicated cycle that cleans the cell until it is finished rather than constantly alternating on and off as before.
Summary
The first salt water pool chlorinator was the IG450 designed by New Zealand company Cascade Pools in 1972. By the time they had designed two subsequent generation machines that attempted to improve upon the initial design, they decided to exit the salt water chlorination market due to ongoing problems with the technology they were unable to properly rectify.
If you’re wondering how the salt water chlorinator market ended up developing anyways, Cascade Pools attended several pool trade shows in the early 1970s with examples of the IG450 and returned a year later to notice that a number of me-too copies of the system had been created by companies from around the world who had clearly stolen their idea. Imitation is the sincerest form of flattery, they say.
Visit Salt Water Pool Report to learn more about this great management option for your swimming pool’s sanitation and don’t forget to read my article What Is A Salt Water Pool to learn more about the overall benefits.