Conflicting readings on salinity

[sound-mind]

Back in early May, given the lack of availability of bleach that I've used previously, I decided to convert to an SWCG. I bought a Circupool CORE55 and 480 lbs of salt, based on my estimated 18k gallon pool. I didn't have a TTK salinity test kit yet, but I ignored common sense and I went ahead and assumed a salinity level of zero :-/

Then I got the TTK salinity kit. The first round of testing came out at 5500 PPM, so high, but then days later 11,800 PPM (!). So I hung my head in shame and drained the pool, filled, got a reading of 6,000, then drained some more, filled, and got a reading of 3600. I was excited!

During this period I was using the generator.

But... now the CORE55 has a low salt light lit. It has only be installed for a month, but the salinity was crazy high. The TTK is saying 3600, but the CORE55 reports that it is too low. Could the high salinity have damaged the cell? I was also considering an issue with the reagent, but it looks like silver nitrate can last forever. Does anyone have any thoughts on what could be going on?

TIA!

 

[Texas Splash]

I do know that there can be a fairly wide swing in testing variance when testing for salt. We use the K-1766 to compare against the unit's own measuring sensors, but even still, it's not uncommon to see a +/- 400 ppm in salt readings. Does your CORE only give a light, or is there a level reading too?

 

[sound-mind]

The downside to the CORE series is that they are pretty basic. Only a few indicator lights, such as low salt, low temp, no flow, dirty cell, and it can only be adjusted in 25% increments. So yup, just a single light lit that tells me low salt.

I'm using the K-1766. I bought a second one since it appeared to be more cost effective than buying the reagent separately, but I was worried about running out when I'm in this situation, so I just pulled the trigger.

 

[DogtownTX]

I had a huge disparity between the K 1766 test kit and the Hayward salt cell reading. The test kit showing much higher. I ended up just using the salt cell reading because that’s the one that will cause it to shut down if it’s too low.

 

[ajw22]

You doing the K-1766 test with a 10ml sample?

 

[sound-mind]

You doing the K-1766 test with a 10ml sample?

And... you hit the nail on the head! My tester was using 25ml. The tester probably used 10ml the first time, giving 5,500, then started using 25ml. Re-tested using 10ml and It now reads 1600.

I would have had to drain some regardless of 10ml vs 25ml since it was 5500, but I am now considering paying someone else to test. I get to deflect blame because I'm color blind and have central vision issues, so I can't read the results and have assigned testing to someone else in the household

Thank you @ajw22 and everyone on TFP. While this is frustrating since I spent swim time draining the pool instead of using it, thankfully I now know what was causing this discrepancy. I already have more salt on the way that I had ordered before the perceived 11,800 reading, but it is slightly delayed due to the current situation.

 

[Rancho Cost-a-Lotta]

And... you hit the nail on the head! My tester was using 25ml.

You're not the first person to use the wrong sample size.

 

[ajw22]

Rest assured you are not the first to do that so it was easy to spot.

It can be confusing with some tests using 10ml and others 25ml. When in doubt send your tester back to the instructions.