Testing Chlorine

We have people who test two different ways. Does this matter?

One person will add reagent #1 and reagent #2 together and shake then record chemical reading.

The other way, they add reagent #1 and shake, take off lid add reagent #2 and shake then record chemical reading.

Are both ways okay?

Thanks for the question

I believe you're using Taylor DPD Reagents which is a good choice. They'll give the most accurate readings. Using a K-2006 or K-2005 will ensure these accurate readings, but there is a way and technique to employ.

It's best if you mix each Reagent separately. Add the drops, shake or stir well, then add the other drops. Mixing them will usually cause a false reading.

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Hope this helps.


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What Would Cause DPD No.1 Water Test To Turn Yellow?

by Chris
(United Kingdom)

I have been testing my chlorine levels using DPD No.1 tablets in a water tester. The results are always pink when adding the tablets. When I topped off my pool with chlorine and did the test, the colour was yellow.

I did notice this batch was DPD No. 3 tablets.

Would this be the cause?

Thanks for the question Chris

The DPD No.1 tablet is used to measure free or "available" chlorine. DPD No.3 tablet is used after the DPD No.1 to measure total chlorine or bromine. The difference between the two is the combined chlorine (chloramine) or bromine.

If I'm reading the question correctly it might be that you may have skipped No.1 and went directly to the No.3 tablet. This may have caused a wrong reading. Or by some chance the factory may have put the wrong tablet in the packet. It does happen from time to time.

When readings look strange, always double check and do another reading. This time really look at what you're doing. If you get the same results, then you know something is wrong. Another reason could be that the chlorine may not have had a chance to fully circulate throughout the system. Sometimes you may hit a "hot spot" of chlorine right after you add it.

I always tell people to wait until the water fully circulates through the system (normally about 10 - 12 hours) after adding chemicals to test the water. For the most accurate readings I would encourage you to look at a Taylor FAS-DPD K-2006 test kit. It has everything you need and the one most pool professional use.

Water Testing Kit

Pool Water Testing

The Pooltester and LaMotte Testing Tablets are the main ones that use the DPD tablets. Hope this helps and have a great swimming season


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