Does cold water affect SWG Salinity Readings?


Active member
Jun 4, 2012
I've read some people who say cold water can cause the SWG not to read salinity properly.

Is there any truth to it? I'm having a problem with my system saying low-salt even after adding 200 lbs in early this week. Panel says pool temperature is 59 degrees at Noon yesterday.

My sensor (3 years old) looked brand new and shiny when I opened it yesterday. Still have to do an acid bath just in case there is scaling.

Thanks for any insights!!!


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

I have a different SWCG, but for me the answer is yes, it matters.

Until the pool water gets above 65 degrees my salt readings are always way too low compared to the actual salt in the pool.

My particular SWCG takes automatic readings 12 hours apart. If it takes a reading early in the morning, it will often be in the Red or "low" salt area... By that afternoon, when the water is warmer, the salt reading will be in Green or good area.

I have the Taylor K-1766 salt test kit just so I can confirm the actual salt level in the pool.

Thanks for posting,

Jim R.


TFP Expert
LifeTime Supporter
Jun 24, 2011
Long Beach, CA
The Jandy Aquapure is more accurate for the salinity than the Pentair SWG for cold water temperature.

It seems all units have issues when the water is below 60 and I suggest to continue using bleach to chlorinate the water until the water hits around 65.

My suggestion is to never add salt without testing the salinity unless you recently loss some due to heavy rains or continued backwashing.

Never acid wash unless there is visible scaling only after trying to remove the scale with a water blast and manual scraping with a wooden object.

As Jim said, I also recommend getting a K-1766 salt test.


Mod Squad
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
I would also suggest that when adding salt to a pool, turn the SWG off. You don't want it to get confused ;) Let the salt dissolve overnight at least then turn it back on.

I second the need for the Taylor K-1766 salt test!

Maddie :flower:


TFP Expert
Mar 2, 2011
What salt reading does the box show and what are you testing the water with to verify the box is correct or incorrect?

Also, get a pool thermometer to verify actual water temperature.


Active member
Jun 4, 2012
Looks like the main board in the control panel was shot. Pool company replaced it and I'm getting normal readings again.

Other Threads of Interest