The differences in Pool Testing Equipment

[Stuamurr]

I recently upgraded to a Palintest 7100 Photometer, from a Lovibond Comparator and various other additional test items, so out of sheer curiosity I did a full test of all of a pools parameters using all the equipment I have available for testing pool water with, it did crop up some interesting results:

The test strips aren't that old, a customer had them when I started doing their pool, so instead of binning them they have just been cluttering up my testing case, but certainly gives good evidence that test strips are horrendously inaccurate. Some of the colours developed on the strips I did have to guess at though as they did not compare to anything on the scales on the side of the tin, which is kind of shocking considering all the parameters are within range.

For the record the pool tested was In Ground, Tiled, holding 36,000 US Gallons, sanitation is Calcium Hypochlorite, source water is Soft = FC ~0.5; CC ~0.2; TA 40; CH 60; pH ~7.0

Stu

 

[chem geek]

Technically, the test strips only test for Total Hardness, not Calcium Hardness. This is true for the LaMotte Insta-TEST^® 5 Plus as with most any other test strip. And yes, not only is the resolution very poor, but the accuracy is as well at least for some of the tests. The accuracy of the FC test for the Hach AquaCheck 5-way is horrible and often much lower than the TC even though there is no CC present.

 

[Stuamurr]

Which therefore makes every reading taken from the strip as wildly inaccurate therefore, and there was me thinking that the only test that faired reasonably on the strip was CH.

The link you provided was indeed the strips that were used, a good case for everyone who has strips to bin them.

As for the FAS-DPD test the colours went clear immediately on the last drop, so the accuracy they tested at agreed with both of the DPD tablet reagents from both Lovibond and Palintest.

Cheers for the feedback.

Regards
Stu