NaCl Upward Drift?

[PointeTaken]

I started my opening process about a month ago. After the rainiest winter on record, my salt levels (along with CYA and CH) were rock bottom. I got the salt up to 3000 ppm, and left it there. Well in the month since, we’ve had two rain events of 5”+ (each) that have required me to pump out several thousands of gallons of water, so I wasn’t surprised when the SWG threw me a low salt alert on Friday. On both the SWG and via manual test, I was down about 400ppm, which was in line with the ratio that I lost CH and CYA as well. I went and got some salt today, and as I always do, I did another test before adding anything. I noticed on the SWG panel that my salt had supposedly drifted back up by 200ppm. To my surprise, my manual test revealed the same increase on two separate tests. That’s the equivalent of 20 pounds of salt. So, anyone know what gives? I didn’t think NaCl levels could drift up without a source of NaCl being introduced to the water! Is there something I don’t know about that can alter the reading? Only thing I did between readings was add some calcium the other day. Maybe that did it?

 

[YippeeSkippy]

Every chemical you add leaves behind some residual salt. I doubt it was 200 more from just Calcium. I think testing variances the more likely explanation.
Also I would never trust the device's salt reading and you should only use the manual test to determine needs for salt or draining

Maddie

 

[PointeTaken]

Also I would never trust the device's salt reading and you should only use the manual test to determine needs for salt or draining

Maddie

Yes, this is why I noted that the manual test reflected the same change as the SWG. While the SWG doesn’t necessary display an accurate level, in my experience (at least with my Hayward unit) they accurately reflect the relative changes in NaCl level. Barring expected variables (adding salt or removing water) I’ve never seen this degree of instability from one reading to another.

 

[JamesW]

Calcium chloride is a salt like sodium chloride.

Calcium chloride will raise the salinity almost as much as sodium chloride.

 

[YippeeSkippy]

Wow! That's a lotta salt .... who knew?! yeah... If anyone knew it would be you, @JamesW

 

[PointeTaken]

Ok, I figured it would raise it some, I had no idea it was almost to the same degree as pure sodium chloride. Thanks, @JamesW!