DPD Chlorine Test Is Cloudy

[cpd515]

When I test my pool for free chlorine using Taylor DPD powder, the sample water remains clear after adding the powder. When I tested my neighbor's pool for the same, the sample water turned very cloudy after adding the powder. This has happened several times. What would cause the test sample to turn cloudy when the DPD powder is added, and is this a problem?

 

[Bama Rambler]

Sounds like bad powder but I'm not familiar with the regular DPD test.

 

[cpd515]

Its a brand new Taylor kit, so I think the powder should be ok.

 

[Bama Rambler]

I'd call Taylor then and see what they say.

 

[CaOCl2]

Most probably the phosphate buffer used in the DPD powder combined with high CH.

 

[GreenLeaf]

As this is the second Google result for "DPD test cloudy".... I just bumped my CH up to 530 from 360 and noticed this change in behaviour immediately, so I figured it must be the calcium I added, and the Taylor's FAQ appears to confirm that and CaOCl2's post above.

The first Google result is...

Technical FAQs

Sample turning cloudy
Cloudiness is caused by a high level of hardness (> 500 ppm) that precipitates out as calcium and/or magnesium salt. To avoid cloudiness, retest this time adding DPD reagents R-0001 and R-0002 first, then carefully adding the sample water to the test cell.

FYI they talk about R0001 and R0002, I'm using the K2006 with R0870 and R0871 but have the same experience.

Also see post #2 here: Chlorine Drop Test Never Gets Totally Clear Anymore

 

[JoyfulNoise]

R-0001/0002 and R-0870 powder are the same chemicals just in different forms and different concentrations. The R-0001/0002 is limited to FC levels below 10ppm while the R-0870 allows the test to be extended up to 50ppm FC.

You can actually use the R-0871 drops to titrate the R-0001/0002 DPD test back to clear.