With an understanding of galvanic corrosion, stains in salt-chlorine pools don’t have to be a mystery.
By Bob Harper
Closing a traditionally sanitized pool is a routine event that many of us have done over and over again. But the spectacular growth of saltwater pools brings new considerations to this old routine.
Cooler weather can mean false alarms for low salt content on equipment. Additionally, balancing the water for the cold takes a more studied approach. Even all-season pools must be treated differently.
Understanding the unique characteristics of saltwater pools — and addressing them with a few simple steps over the winter — can help guarantee a smooth opening in the spring. (For more on conductivity and temperature as they relate to saltwater, click here).
Many electrolytic chlorine generators (ECGs) contain sensors that monitor the conductivity of the water and alert pool owners when salt readings are too low. The higher the conductivity, the higher the level of salt.
This metric works well during the summer, but can cause problems when the weather turns cool. Since cooler weather decreases conductivity, some ECGs may show low salt levels and alert the pool technician to add salt.
An over-salted pool may not exhibit signs or problems until the pool is opened in the spring. But at start-up, too much salt may cause the ECG to shut down until water is diluted to achieve normal, operational salt levels.
The problem can be intensified by the fact that most ECG sensors can’t be calibrated. So an ECG may give a different reading than an external electrical reader that is cleaned and calibrated regularly, and therefore more accurate.
Using salt test strips should give you accurate results, regardless of the temperature outside.
In addition to causing problems with conductivity readings, colder temperatures also can impact the natural tendency for water to cause corrosion in pools. Lower temperatures decrease the Langelier Saturation Index (LSI), which indicates whether pool water is properly balanced. If the LSI is too low, corrosion can damage pool surfaces and equipment.
Fortunately, these issues can be addressed by taking a few important steps as colder weather approaches.
First, all saltwater pools should be balanced prior to any winterization, with special attention given to pH, total alkalinity and calcium hardness.
Then help prevent staining and scaling throughout the winter by adding a high-grade stain and scale sequestrant that’s designed specifically for saltwater pools. The sequestrant ideally circulates in the pool with the pump running for at least eight hours prior to shutdown.
Next, for pools that will be closed for the winter, you’ll need to winterize the ECG according to manufacturer instructions. Typically, this means disconnecting the power source and draining all water from the unit. (Some manufacturers say you can leave the ECG outside if you winterize it properly, but if the unit can be disconnected and brought inside, there’s no harm done.)
If the ECG will remain connected and below the pool water level, with any possibility of water residing in the unit, it should be disconnected from its power source and protected with a nontoxic antifreeze. However, this is not an ideal alternative.
Saltwater pools that remain open during the off season have some different considerations. In cooler areas of the country, water conditions typically will drop below the ECG’s programmed cutoff level. (Many models with built-in temperature sensors are programmed to turn off when water temperatures drop below a certain point, generally 50-59 degrees F.) These pools will require an alternative chlorine source to keep the water sanitized — ideally, a fast-dissolving type such as liquid chlorine (bleach), dichlor or lithium hypochlorite.
If water conditions will not cause the ECG to automatically turn off, it’s best to set the ECG at a chlorine output level that will maintain the ideal 1 to 4 parts per million of chlorine throughout the off-season. The appropriate level should also take into consideration the amount of time that the pump will run each day, since ECGs will turn off automatically when there is no water flow.
For pools that remain open, be sure to educate your customers about automatic low salt alerts, and why these alerts occur. If your customers do get a low-salt alert, they can provide you with a water sample, which you can warm up to room temperature and test with a reliable method (salt conductivity meter or test strips) to determine the true salt level.
Obviously, the better saltwater pools are treated during the off-season, the better they’ll look in the spring. Your customers will enjoy water that’s clean and clear, and equipment that works as well as it did the summer before.