By Sean Assam
One of the fastest growing accessories in the swimming pool and spa industry are electrolytic chlorine generators (ECGs), which also go by the name of salt chlorine generators (SCGs), saltwater chlorinators and saltwater generators. They all do the same thing—produce chlorine onsite. The popularity of this sanitation method is increasing in both the residential and commercial pool/spa markets; however, there is a lack of understanding in terms of how these systems work, how they are maintained and how to properly diagnose and troubleshoot a system to ensure successful operation year after year.
What is an ECG?
An ECG operates using several components, including a control unit, electrolytic cell, flow switch and salt.
The control unit takes line voltage, usually factory supplied at 220 volts, and converts it to a low-voltage, direct-current (DC) power to the electrolytic cell. It also controls the amount of chlorine produced, provides system diagnostics, and in some cases, it provides control of the circulation pump.
The electrolytic cell houses the system’s titanium blades, which have a catalytic coating of Ruthenium Oxide (RuO2). Over time, this coating is sacrificed to generate chlorine, which means it will need to be replaced when it wears out. The lifespan for a typical residential cell is approximately 10,000 hours of chlorine generation, while a commercial cell will last for approximately 15,000 hours.
According to UL Standards 1081, Swimming Pool Pumps, Filters, and Chlorinators, a flow detection device must be designed into the ECG. The two acceptable methods for flow detection are mechanical flow switches or electronic gas traps. A flow switch places a flat paddle in the stream of water and pushes it to activate a micro switch when there is sufficient flow.
A gas trap uses the water’s conductivity to close the circuit between two points within the cell. When there is insufficient flow, gas generates within the cell body and opens the circuit between the two points, shutting off power to the cell.
The most important component, salt, or sodium chloride (NaCl), is added for two reasons. First, it increases conductivity in the water to create the electrolytic reaction, and secondly, it is the source from which chlorine is generated.
The electrolytic process generates hypochlorous acid (HClO) to create sustainable chlorine residuals by recombining sodium to chloride. During this ongoing process, salt does not diminish; it is reusable, making this an efficient method of water sanitation.
Further, this process generates chlorine at a high concentration within the cell, providing efficient and effective treatment of water passing through the cell. At this point, breakpoint chlorination is also reached, which eliminates the negative effects of chloramines (NH2Cl) caused by chlorine reacting to bather waste (e.g. body oils, cosmetics, suntan lotions, perspiration, urine, etc.). The result is better water quality, and in the case of indoor pools, air quality as well.
Salt levels should be tested quarterly and/or after heavy rain fall. For winterized pools, levels should be tested at the beginning of the season and at least once during the season.
Since salt is not lost by evaporation, it should not fluctuate too much. If salt test levels are inconsistent with the salt display on the control unit, it should be calibrated to match the test results (if possible). Keep in mind, some systems provide a salt-level estimate, based on the amps and volts to the cell, which are influenced by water temperatures and remaining cell life (lower salt level displayed). In cold temperature conditions, or with an older cell, salt levels should be verified first by testing the water prior to adding more salt.