Spa Equipment Corrosion – Saltwater

Pool and Spa equipment and metal corrosion problems are usually caused by water balance issues and not saltwater. Water is known as the universal solvent and under the right conditions will slowly dissolve just about anything with or without salt. If the pH,alkalinity and/or hardness are low, your heater and any other metal parts will be slowly destroyed. Spas using chlorine or bromine tablets experience heater corrosion for this very reason, because the pH and alkalinity drop to an unacceptably low level which causes the water to be “corrosive”. Chlorine generators will not cause the pH and alkalinity to drop to low levels but if the hardness levels are too low, the water will dissolve metals or whatever it can to achieve correct saturation. Everyone knows the effect of putting a penny in a glass of soda and how it will dissolve the penny. This is due to the water being corrosive because of the low pH and alkalinity caused by the carbon dioxide which creates carbonic acid and this happens rather quickly. Try putting a penny in a container of distilled water for 2 or 3 months. You will notice the penny slowly dissolve because the water is trying to saturate itself with minerals.

Most saltwater chlorine generators these days operate on salt levels of 2-3,000 ppm which is considered fresh water. Not enough to cause corrosion like sea water which is about 35,000 ppm of salt. Many pools and spas treated with liquid chlorine have salt levels higher than that especially in drought years in California when draining a pool is highly discouraged. Occasionally, one of these pools would experience galvanic corrosion due to the water being more conductive from the higher salt concentration and low level electrical currents in the water caused by improper grounding of nearby power supplies. The pool would become the ground for these stray currents and cause corrosion. All of the major equipment manufacturers make saltwater chlorine generators and most of them work on a 2-3,000 ppm salt concentration. If the salt was the cause of equipment damage, the manufacturers would discontinue the products due to warranty expense. There are now at least 2 spa manufacturers that have a saltwater chlorine generator as an option on their new tubs. ControlOMatic recommends a low salt level of 1500 to 2000 for all chlorine generator models.

One of the biggest causes for spa damage with a chlorine generator is over-chlorination. If not adjusted properly the chlorine generator can make too much chlorine and over time it builds up to very high values. Make sure to measure the chlorine level before use and follow the instructions to properly adjust the power level.

If you want to use a chlorine generator the best thing to do to avoid possible issues are:

  • Make sure your water calcium hardness is at least 200 PPM
  • Make sure you have proper grounding of your equipment
  • Make sure to have the chlorine production adjusted properly, excessive chlorine can lease to corrosion

2 Comments

  • glenn urban

    Reply Reply April 16, 2016

    Our unit for our tub was just sitting for about six months due to an electrical problem leading to the tub…we didnt want the water fouling, so left the unit in…for six months it just sat…we fixed the electrical feed to tub finally..the chlorinator was using a long extention chord to it was operational…for some reason, and we think this is the case, the lights on the unit do not come on anymore, but, it appears to be generating choline still? the chlorine level in the tub is off the charts…could there be so much chlorine that the unit is just not coming on now?

    Thank you for any help you can give us.

    • admin

      Reply Reply April 27, 2016

      Hi Glen, looks like you have the MiniChlor. The lights should still come on, and if it was on and making chlorine the last 6 months probably with the water temperature low the chlorine would be through the roof which can damage the spa. You can return the unit to us for evaluation and you may want to upgrade to our new SmarterSpa which will not make too much chlorine as it measures it to determine when to turn on.

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