So I have been playing with the pool water chemistry for about a month now. I have been using the K-1000 OTo for quick testing( comes with the TF-100.) The DPD test question: my 1st time doing this type of testing so forgive my dumb question: when I add the suggested amount of powder the sample turns pink, ok did that right. then I put the drops in and count until it turns clear, ok did that right, But, then a few seconds later it turned pink again??? Do I begin adding drops again and continue counting? Yes i am swirling each drop.