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
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
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,
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
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.