AquaCheck salt strips VS K-1766 drop test

[Brentr]

I was trying to recalibrate my Aquarite SWG so I wanted to get an exact reading. I have reason to believe that it was never calibrated however I thought the cell was not producing chlorine. Here are the results
AquaCheck strip test says 3270ppm (put in 1 inch of water) Tested it twice
K-1766 test says 4400ppm (using Apollo Stirrer) Tested it twice.
Aquarite SWG says 3200ppm
So which test should I believe.

BTW here are the full results
FC- 14
CC- 0.5
TC- 14.5
PH- 7.6
TA- 90
CH- 310
CYA- 90
TEMP -90
BORATE- 50
Water is sparkling.

 

[Griswald]

As long as the SWG is happy, the numbers dont really matter

 

[pooldv]

Salt tests are +/- 200-400 ppm. And your salt reading on your SWG isn't really a salt reading it at all. Salt tests are designed to get you into the ballpark to make sure you aren't way low or way high. As Gris says if the SWG is happy and making chlorine and the salt test is between somewhere between around 3000 and 4500 ppm then life is good in salt land.

 

[Major_in_MS]

Looking at your full test results, just remember that your pH reading is not accurate because your FC of 14. The pH test should only be done when FC is less than 10.

 

[JamesW]

You can't recalibrate the AquaRite. If the cell is over 5 years old, it's likely to be underperforming. An underperforming cell will cause the box to read lower than actual. Check the cell for scaling and clean if necessary. Don't clean with acid unless necessary and only with the most dilute acid that is effective.

 

[Brentr]

You can't recalibrate the AquaRite. If the cell is over 5 years old, it's likely to be underperforming. An underperforming cell will cause the box to read lower than actual. Check the cell for scaling and clean if necessary. Don't clean with acid unless necessary and only with the most dilute acid that is effective.

I came across this on how to recalibrate AquaRite SWG
How To: Recalibrate the Salt Level on a Hayward Aqua Rite - YouTube

 

[JamesW]

It's not a recalibration. It merely resets the average salt reading to the instant salt reading.

Can you post all of the diagnostic readings?

 

[JoyfulNoise]

Just to answer your original question - the K-1766 is the most accurate representation of your salt levels. The K-1766 is a chemical test that measures the exact chloride ion (Cl-) concentration in water. It has no interferences (unless you put cyanide in your pool or you have a mixed chlorine/bromine pool) and it can be made more accurate by simply using a larger water sample - 10mL sample has a precision of 200ppm/drop while a 25mL sample has an 80ppm/drop. I won't go into the chemical details, but it is a highly accurate test.

The test strips, hydrometers, SWG output and handheld TDS electronic meters are all proxy methods of measuring salinity because they measure something other than salinity that is affected by the salinity of the water. So, in the case of those strips, the technique being used is capillarity. The capillarity of those strips (how high the internal water level rises) is affected by salinity. However, it is also affect by other chemicals in the water, how much water you add to the sample tube that the strip sits in, the temperature of the water sample, etc, etc. Electronic meters measure conductivity and the conductivity of water is affect by all the ionic species in water, not just the chloride ion concentration. Most proxy methods of measuring salinity are not much better than +/-400ppm. Electronic meters can be calibrated with standard conductivity solutions to get better accuracy BUT few people do that and fewer still regularly calibrate them.