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A case for borates: Maintaining water chemistry in pools using salt chlorine generators

By John Bokor

One of the primary reasons borates have gained popularity is its ability to control corrosion in a saltwater pool environment.
One of the primary reasons borates have gained popularity is its ability to control corrosion in a saltwater pool environment.

Electrolytic chlorine generators (ECGs) or salt chlorine generators became extremely popular about 15 years ago and have continued to grow throughout Canada and 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?

Borate products are available in powders and slurries and should be added directly to the pool.
Borate products are available in powders and slurries and should be added directly to the pool.

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.

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