Electrolytic chlorine generators (ECGs) or salt chlorine generators became extremely popular about 15 years ago and have continued to grow throughout the U.S., simply because pool owners love them. However, as most in the industry know, some pool owners believe that after installing a salt chlorine generator nothing else is required in terms of water maintenance.
In the short term, relying solely on an ECG system to take care of the pool’s water quality will initially result in clear water. However, when additional water treatment products and/or applications are not introduced for weeks and/or months at a time, the lack of monitoring/adjusting water balance parameters and sufficient oxidation will eventually lead to various water complications. Therefore, it is important the industry addresses proper water maintenance regimens and educates consumers about using these devices.
Specifically, consumers need to know an ECG alone will not solve all of their water maintenance needs and that this equipment has its own specific maintenance requirements.
In conjunction with salt chlorine generators, pool professionals also need to explain other methods of keeping pool water clean and clear, which allow the equipment to continue to operate properly while keeping in mind the overall health of the pool and its surroundings.
What do salt chlorine generators do?
ECGs produce chlorine on-site—using salt and electrolysis—to sanitize the water. As a result, chlorine does not need to be stored or manually introduced into the pool by the homeowner. Water from the pool containing salt (sodium chloride) enters the ECG cell (NaCl + H2O). Once inside, an electric charge is applied to the water using electrolytic plates, which splits the water molecule (H2O), and turns chloride ions into chlorine (hydrogen) gas. Then, as the chlorine gas dissolves into the water, pure chlorine is returned to the pool.
Most ECGs are installed in-line and produce chlorine only when the circulation system is operating. For these systems, a large amount of pool-grade salt is added into the pool to establish a concentration of about 3000 to 5000 ppm. In-line generators are installed on the pool’s circulation return line and available chlorine is generated when dissolved salt passes through the device. In addition to assuring the ECG is functioning properly, it is important to maintain the appropriate salt concentration, as too much salt can increase the potential for corrosion.
Further, pools with salt chlorine generators continuously generate sodium hydroxide (NaOH) (when the NaCl is broken into free chlorine). Unfortunately, NaOH has a pH of around 13, which will quickly increase the pool’s pH. The continuous addition of NaOH results in a never-ending rise in the pH of the pool water. If this is left to run rampant, the high pH will lead to corrosion of pool components.
Side effects of salt chlorine generators
Inherent in the way salt chlorine generators work are ‘side effects’ that can adversely affect the successful operation and appearance of a pool—namely corrosion and scale. Fortunately, borates can be used as a simple way to overcome many of these side effects. They are administered to the pool one time, typically a once a year application. Borates are an extracted earth mineral that possess several benefits to recreational water. They are unique in that they remain in the water and are only lost through water removal (e.g. splash out or backwashing). Adding borates during pool start-up is ideal, as they serve as an additional buffering system for the water.
How borates can help in pools with salt chlorine generators
One of the primary reasons borates have gained popularity among pool service professionals is its ability to control corrosion in a saltwater pool environment. Borate products are available in powders and slurries and should be added directly to the pool.
Borates have a buffering ability that allows pool water to remain at a more neutral pH level for a longer period. This, in turn, allows the chlorine to be more efficient and effective at sanitizing the water.
As mentioned earlier, the electrolysis that occurs in the ECG can cause de-plating problems on handrails, light niches, and other metal components. Borates create another buffering system for the water that eliminates these effects.
Many pool professionals agree that borates are a good companion product to salt chlorine generators because they assist in making pool water maintenance easier. ECGs are sold to make sanitizing pool water easier; therefore, the last thing a pool professional wants is for this equipment to cause additional maintenance issues.
“It worth the consumer’s extra investment in a borate product,” says Jonathan Schulhoff, retail manager at Arthur Edwards Pools in Long Island, N.Y. “Borates add an anti-corrosion effect that helps protect against rust on equipment, accessories, and fixtures around the pool. Our customers who use borates are never in the store with rusted ladders—even the vinyl liners seem to last longer.”
Calcium scale prevention
High calcium content can lead to scale formation (as well as cloudy water). Scale forms when calcium and carbonates crystallize on the pool’s surface, walls (around the waterline), and equipment. This problem is compounded by high pH. Borates keep pH from creeping upwards to help prevent scaling.
With the increased installation of ECGs, borates have become even more important because scale can reduce the life of the cell plates in the salt chlorine generator. By maintaining borate levels at 50 ppm in pools equipped with salt chlorine generating systems, pool professionals will find salt cells last much longer.
“Salt conversion cells on chlorine generators in pools where borates are used can easily last a decade,” says Schulhoff. “Even customers who ensure their pool water is balanced typically only get five to six years out of an equivalent cell.”
The reason salt cell lasts longer when borates are used is because it bi-chelates (or bonds) with calcium present in the water, allowing the cell to remain cleaner because less scale forms. Although scale does form in some cases, it is a much ‘softer’ scale that is easier to remove. Further, as less acid is required to clean the cell plates, plate damage is minimized as well.
Due to the high pH at the surface of the cathode plates within the ECG, scale formation is highly likely. In fact, it is important to note scale formation will occur inside the salt chlorine generator even if the pool water is properly balanced.
According to Schulhoff, his service teams start up all of their new pools with approximately 30 to 50 ppm of borates in the water, which normally lasts between one and two years. After about a year-and-a-half, they test the water and usually need to add a little more borate to get the level back up into that range.
Additional benefits of borates
Borate-based products also inhibit the ability of algae to reproduce.
“Our customers who use borates in their pool never have problems with green water,” says Trey Theobold, the retail manager for Riverbend Sandler Pool Supply in Plano, Texas. “After it rains once or twice in the summer, and the temperatures get up to 100 F (37.7 C), all of the pools in our region turn green. However, all of our customers using borates never experience green pools.”
Due to the number of clients using this product, testing for borates is part of the water maintenance program offered by Riverbend.
“We use the spin tests which actually test for borate levels,” says Theobold. “We also find borates help to keep the pores of the pool plaster clean and algae-free. Otherwise, algae likes to grow in these areas of the pool wall.”
Although borates are mainly a tool for pH and algae control, pool owners also like the way it makes the water look and feel. This product actually increases the refractory index of the water so more light is reflected which gives the pool more ‘sparkle.’
Finally, all borates are considered derivatives of boric acid B(OH)3, the active ingredient in eye drops, which provides the soothing effect. As a result, pools and hot tubs treated with borates also offer the same feeling and, in effect, help to improve the overall bathing experience. In addition, because borates are a mineral salt, they help make bathers’ skin feel softer and help reduce ‘red eye’ from swimming.
With so many pools using ECGs, there is a definite case for using borates. Adding them once a year can make all the difference to a pool owner who chose a salt chlorine generator to simplify their pool water maintenance.
This article was written by John Bokor and originally appeared on Pool & Spa Marketing [link].