Weird test results for Chlorine

[waterbear]

I'm sorry all, but NOW I am really confused! So....if I do the first test with the first set of drops and the color shows about "3" on the color match (it IS pink) then am I o.k. and I can skip the second part (adding the other 5 drops and then doing the math?). Sorry, but this thread totally confused me....

in a nutshell, no. The first part of the test will tell you your FC level. This is the 'good' chlorine that you want in your pool. the second part then measure the total chlorine, which is your FC and any CC (the 'bad' chlorine) in the water. If you have CC this test will darken. Usually you cannot detect CC under about 1 ppm with this test so if it does darken , even a bit, you should shock your pool to get rid of the combined chlorine. If the test darkens enough to be able to read the level on the comparator you can get a reading for your CC. For example, you add the first two reagents and get a FC of 3 ppm, then you add the last reagent and the color deepens to 4 ppm TC. You then subtract the FC from the TC to get your CC....TC-FC=CC which in this example would be 4-3= 1 ppm CC.

Also, the results for TC with a DPD test might not match up with the number for an OTO test for TC (turns yellow). This is normal. OTO is a very rugged test and will work with very high clorine levels but it is hard to get the precision at lower levels because the color changes are subtile and more difficult to read. Think of OTO as a good 'quick and dirty" test for your chlorine for a daily check just to make sure nothing is wrong. An OTO test should be allowed to develop for a minute or so before you read it. DPD tests for FC needs to be read immediately and the TC needs about 30 seconds to develop fully.