TECHNOLOGY ELECTROLYSIS AND CORROSION CAUSED BY SALT CHLORINATORS
Are the pools and equipment pieces at risk?
By David Barnsley
Due to the high popularity of salt chlorinators for residential pools in North America, dealers and manufacturers are trying to learn more about the salt technology, about how to install these systems and how to make them work. Unfortunately, there are still a lot of confusion and misinformation about the optimal operating conditions of salt chlorinators.
Some are concerned that the chlorine produced by the salt can attack and discolor the pool’s plaster and squint vinyl liners, and contribute to corrosion of pool accessories and of some parts of the water heater and gas heather. Dealers must have received adequate training in order to explain to consumers the capabilities and limitations of this technology.
“I NO LONGER NEED TO TAKE CARE OF MY POOL’S WATER”
“I no longer need to take care of my pool’s water.” This is one of the major misconceptions that pool owners have about salt chlorinators. The manufacturers claim that salt chlorinator’s technology eliminates the need to manually add chlorine to the pool water, but the salt concentration must still be manually checked, the water tested, and one must maintain an appropriate chlorine level and proper chemical balance (total alkalinity, calcium hardness and PH).
Dealers must tell their customers that maintaining the chemical balance of the water – including shock treatment and water stability – is essential and can not be neglected, even in the case of a pool with a salt chlorinator. The promotion of these systems as a magic solution to eliminate the need to test and maintain the water does not do justice to the technology.
”Dealers must be honest with consumers about the need to maintain a proper chemical water balance, otherwise they could blame the equipment in case of problems”, says Latif Mawani of Zodiac Pool Care Canada Ltd., a manufacturer of swimming pool chlorinators.
“Chlorine produced by salt chlorinators is not more harmful to the pools then traditional chlorine,” says Latif. “The majority of the problems found in pools with a salt chlorinator come from a chemical imbalance in the water or a chlorine rate too high. Salt chlorinators are often singled out because it is easier to find a culprit than seeking the source of the problem”.
Another misconception is that it is that pools equipped with a salt chlorinator are equivalent to swimming pools filled with sea water and that the water has a salty taste. Obviously, there are differences between a pool filled with sea water and a pool treated with a salt chlorinator. The salt concentration of seawater is greater than 25,000 ppm, and water heaters and equipment for sea water pools must always be designed specifically for this type of pools. The salt concentration produced by the salt chlorinators varies from 3 000 to 4 000 ppm standard in residential pools, which is well below the taste threshold.
LOW SALT CONCENTRATION AS A SOURCE OF CORROSION?
Dealers and contractors often wonder if the relatively low concentration of salt produced in a pool with a salt chlorinator can corrode the pool equipment. According to Charlie Mousseau of CL Harrington Marketing, in Calgary, Alberta, a company offering salt chlorinators for residential or commercial purposes, the misconception most often conveyed about salt chlorinators, is that they cause corrosion.
“A salt concentration less than 6000 ppm does not cause corrosion. A regular chlorine level of 4.0 ppm is 10 times more corrosive to stainless steel then a salt concentration of 4000 ppm, “says Charlie.
Sue Robach, Technical Training Officer at Pentair Water Pool and Spa, located in Sanford, North Carolina, a manufacturer of a range of equipment for swimming pools and spas, including salt chlorinators, water heaters for swimming pools and spas and heathers; indicates that the concentration of salt in the pool water is not high enough to cause corrosion and electrolysis.
“Salt is a corrosive element – but not at the concentration found in pools with salt chlorinators,” says Sue Robach. “The electrolysis usually occurs in pools with electrical systems (eg. Lighting system), which can have an effect on heat exchangers – but using a salt chlorinator does not cause excessive corrosion or electrolysis if the water chemistry is good and that the electrical installations comply with the standards. Extremely high levels of chlorine over a long period of time, regardless of the source of production of chlorine can cause corrosion and damage to the equipment, but constant monitoring of the water’s chemical balance minimizes the effects of chlorine on the pool’s equipment.
Peter Owenson, Chief Product Manager of heating products for swimming pools and spas for Jandy Pool Products in Petaluma, California, a manufacturer of water gas heaters, heat pumps and chlorinators, also advises on the matter.
“The salt chlorinators can contribute to corrosion of pool equipments if they have been improperly installed or poorly maintained,” says Peter. “The salt added to the water can indeed create corrosion or erosion problems, but when the water system flow operates at a speed too high or too low, the risk of failure is higher. ‘
“If the salt concentration is maintained at a level not in accordance with the manufacturer’s recommendations, problems could occur. It is therefore very important to measure and maintain the salt concentration”.
As additional protection against corrosion of pool equipment with a chemical imbalance or whose salt concentration is not properly maintained, some manufacturers now offer pools, rails, ladders, anchor brackets and divers specially designed to withstand the
effects of salt.
“We offer swimming pool accessories such as ladders, rails and anchor brackets made of highly resistant polymer and designed to be used with chlorinators,” said Michael Harvey, Vice President of Planning and Business Development at FeherGuard Milton, Ontario. “This non-conductive material, also resistant to chemicals used in swimming pools will not rust, will not make holes and will not flake. Even the nuts and bolts used to manufacture our scales are No. 316 stainless steel to prevent corrosion. These products have been developed over the last 20 years for commercial use, but the market for residential pools equipped with salt chlorinators now takes advantage of it”.
NO PROBLEM IF THE POOL IN PERSPECTIVE IS EQUIPPED WITH A GROUNDING SYSTEM AND VOLTAGE REGULATOR.
Maintaining proper water chemical balance and the right concentration of salt in the water are not the only ways to protect from corrosion pools with a salt chlorinator. Manufacturers of chlorinators, water heaters and gas heathers agree that swimming pools must also be equipped with a voltage regulator and grounding system.
“The problem is that corrosion is not caused by salt chlorinators, but rather by a voltage regulator inadequate for the electrical parts,” says Emmanuel Amadio, electrochemist and product specialist at Hayward Pool Products Canada Inc., located in Oakville, Ontario. “The same problem occurs in pools using a standard chlorination system or other sanitizer’s types”.
According to Emmanuel Amadio, a voltage regulator circuit is defined as the electrical connection between each piece of pool equipment requiring a similar voltage threshold. When equipments are using the same potential or electric current, they are said “equi- potential”. All equipment (pool walls, pumps, lighting, rails, ladders, etc.) forms a grid that creates a common bond “equi-potential” system. On the other hand, the ground is defined as the electrical connection to the earth system in order to ward off the electrical current (amperage) of the equipment in case of failure.
Mark Manning of Watermaid Canada Inc., A manufacturer of salt chlorinators in Richmond Hill, Ontario, emphasizes the meaning of these terms.
“Electrochemical corrosion occurs when a low current intensity occurs between two metal work pieces having different electrode potentials. To prevent this, make sure that the pool has a good voltage regulator and grounding system. If all the elements that corrode are properly connected, there will be no potential difference between chemicals and, in the absence of potential difference; there is no current flow and corrosion, “says Mark Manning.
He also mentions another way to prevent damage to the equipment for pools equipped with salt chlorinators. It is to insert another pin grounded near the pool where the humidity, the composition soil and the electric potential are as close as possible to those of the pool.
“The problems start when sometimes the grounding rod of the pool’s equipment is installed under the eaves where the soil tends to be dry compared to the ground near the pool,” says Mark. “This can create a potential difference between the water and the pool equipment at the contour of the pool that is isolated by the vinyl liner. Additional rod grounding eliminates this potential difference. ‘
Bruce Sunley Rheem of Canada Limited in Mississauga, Ontario, a manufacturer of Raypak gas water heaters for pool and spa and heat pumps, reiterates the importance of an adequate bond to prevent water heater corrosion in a pool equipped with a chlorinator.
“The pool must have a proper electrical connection, while the water heater itself must be connected to the same ground pin,” says Rheem.
“This helps prevent the risk of electrolytic corrosion resulting from the electrolysis process triggered by the chlorinators”.
ETCHING IS NOT A PROBLEM IF THE CONCRETE DRYING TIME IS SATISFACTORY
For the recently built concrete pools, some people in the industry say that chlorinators can attack the surface of the pool, but the pool builders believe that this is not a problem if you let the concrete dry for at least 3 months prior to the use of a salt chlorinator. Other entrepreneurs believe that concrete needs to dry only one month.
“We usually recommend that customers do not use their salt chlorinator in the month following the date of starting the circulation system of the water,” said Ed Trasolini E. Trasolini Pool Construction Ltd., A manufacturer of concrete pool and spa located in Vancouver, British Columbia. “I think waiting 3 months is somewhat exaggerated.”
Melissa Brown of BonaVista pools in Markham, Ontario, another manufacturer of concrete pools, thinks a one month pause before starting the salt chlorinator is sufficient.
“We have established a policy whereby we add salt to the pool water a month after the drying of the concrete is completed. We also suggest to keep the chlorine level at its lowest to minimize its effects on the concrete, “says Melissa.
In conclusion, salt chlorinators are the ideal choice to maintain chlorine residuals
consistent and stable in the pool water, providing that the pool owner understands what the capabilities and limitations of this type of equipment are. Dealers must emphasize the importance of maintaining the chemical balance of the water, good salt concentration in a pool with a system voltage regulator and grounding. This is the only way to end the blaming of salt chlorinators for the corrosion occurring in swimming pools.