Odd Color Change when Testing for Chlorine

[RudyandRocky]

I am using a full testing kit with 5 drops of R-0001 DPD Reagent #1 and 5 drops of R-0002 DPD Reagent #2 to test for chlorine.

When I put in the reagents they immediately show a FC reading of about 1.5 to 2.0. Within about 2-3 minutes the water in the test tube turns a strange light gray purple. I've never had this happen before. Could it be my chemicals have gone bad? They are about six months old.

Alk - 100
CH - 180
PH - 7.5

I have an "endless" pool that is only about 2800 gallons. I use standard Chlorox bleach to sanitize and the occasional Borax or Baking Soda to adjust. I do have to add Muriatic Acid periodically but not more than every other week. The pool is covered all day and I am the only swimmer so I keep the chlorine relatively low. There is any stabilizer in the water right now. The only other chemical I have added is a water clarifier.

[waterbear]

I have seen the LaMotte reagents turn that color on the FC test after standing a few minutes. LaMotte says the FC should be read within 30 seconds of performing the test. From the reagent numbers I see you are using the Taylor reagents. I have not experienced that with them but I am going to test tomorrow and let the test sit to see if it develps the same off color I have seen with the LaMotte reagents. Might be normal, especially if the DPD solution is getting old.

[RudyandRocky]

I bought new reagents and my chlorine readings are much higher and it doesn't turn the funny color. Interesting, because the reagants weren't very old.

Anyways.............now I know what to look for.

Thanks!
Mickey

[waterbear]

DPD reagent #2 does have a shorter shelf life than the rest of the reagents in the test.