Salt level accuracy - strips vs AquaRite

[danandmanda]

Which should I trust, the reading from Sodium Chloride test strips (400-7000PPM) which has me dialed in at 3200 ppm or the reading on my Hayward Aqua Rite which is showing 3800 ppm?

 

[JoyfulNoise]

Neither give you a true salinity reading. Only the K-1766 test kit gives the true salinity reading as it chemically determines the chloride ion (Cl-) concentration and converts that to ppm of NaCl. Every other test method is a proxy measurement with very wide margins of error. Strips can easily go bad from humidity exposure or give you a false reading if the test solution isn’t at the right level. The SWG is just an electrical conductivity probe (TDS) where the manufacturer has calibrated the output. It can drift with temperature or cell age. Aquarites are probably the most accurate of the SWG’s but that’s like saying Little Johnny over at the Arizona School for the Visually Impaired is the best marksman in his class because he can actually point his gun in the right direction....get a K-1766 and you’ll never have to wonder again.

 

[Divin Dave]

^^^what he said^^^
And even with a K1766, the test is only accurate to 200ppm which is better than any other salt test method short of a mad scientist laboratory. The strips margin of error (if they are in good shape), is only about 500ppm.

 

[chebyshev]

I've just converted to salt and had a similar question. I tested 4 different ways the other day and got:

K1766 - 3200 ppm
Pool Store - 3000 ppm
Strip - 2700 ppm
PureLine SWG - 2400 ppm

I've since added 40 lbs of salt because all the readings were below where I want to be (3600 ppm).

Sounds like I should believe the K1766? Can I make the SWG stop complaining about low salt concentration?

 

[JoyfulNoise]

When the SWG readout is that far below actual value, two possible causes are - (1) an aging cell with deteriorated coatings on the plates, OR (2) calcium scale on the SWG plates. You can pull the cell and acid wash it according to the manufacturers direction to see if that helps. Just know that every acid clean deteriorates the cell coating further so, if visible calcium scale is not present, then there’s no point in acid cleaning the cell.

 

[chebyshev]

The cell is brand new, I just installed it myself a month ago.

 

[ping]

Have you looked to see if scale is inside the cell? With improper water balance for SWG's, cells can build up scale very fast.

 

[Jnet]

I'm obsessive about keeping my CSI in line. I installed a Pureline system in 2017 and it has chronically read low salt since day one. Other than that, it's great. I just trust my K1766 and carry on...