Difference in PPM, which one is correct?

[PoolDoc]

I wouldn't worry, simply because of a variation in test results.

As far as calibration -- some can be. Look up your exact model manual here,
http://www.hayward-pool.com/ctg/In-G...01_14006_Y.htm
and see.

[steveinaz]

I have the Taylor kit Ben mentioned---soooo much eaiser than the strips, with accurate, repeatable results.

[mas985]

As far as calibration -- some can be. Look up your exact model manual here.

The Goldlines cannot really be calibrated for salt level. The best you can do is replace the average salt level (shown in main display) with the instaneous salt level (shown in the SWG diagnostics menu) which explained in the manual.