Chlorine Tests: Test Strips, Test Kits, Test Meters, and Replacement Reagents
Chlorine Chemical Symbol

Wikipedia describes chlorine as... "the chemical element with atomic number 17 and symbol Cl. It is a halogen, found in the periodic table in group 17 (formerly VII, VIIa, or VIIb). As the chloride ion, which is part of common salt and other compounds, it is abundant in nature and necessary to most forms of life, including humans. In its elemental form (Cl2 or "dichlorine") under standard conditions, chlorine is a powerful oxidant and is used in bleaching and disinfectants, as well as an essential reagent in the chemical industry. As a common disinfectant, chlorine compounds are used in swimming pools to keep them clean and sanitary."

Most people assume chlorine testing only applies to pool water, but in reality, a person can find chlorine in many municipal water supplies, private wells, and in numerous manufacturing processes. Each application demands a different amount of chlorine and therefore each application requires a different testing method for chlorine concentrations.

DPD -- The most common method for testing chlorine concentrations involves the use of a chemical known as DPD (N,N Diethyl-1,4 Phenylenediamine Sulfate) which comes in powder, tablet, reagentstrip, and liquid form. Each form of DPD has its advantages and disadvantages. DPD & Chlorine in Water

The addition of DPD to water samples containing oxidizers such as free chlorine, bromine, iodine, chlorine dioxide and/or permanganate results in the formation of a reddish tint to the water whose intensity directly relates to the amount of oxidizer(s) present in the water sample.

Click here for more information on DPD.

OTO -- Commonly used in the pool & spa market for quite a long time, the addition of OTO (Orthotolidine) to water containing certain oxidizers, usually chlorine or bromine, will result in the formation of a color ranging from pale, light yellow to blood red. OTO and Phenol Red Test Kit for Total Chlorine and pH

Although many test kits for pools and spas still pair OTO up with phenol red, a chemical used to measure pH, because of how simple the two chemicals make water testing, OTO tests only for total chlorine and provides semi-quantitative results at best.

Most swimming pool and drinking water professionals agree that free chlorine levels matter much more than total chlorine levels when it comes to the sanitizing and disinfecting of water.

Looking for general information on water testing, water quality issues, and other topics related to the testing of water for drinking, swimming, industrial and other applications? Below you will find the most recent addition to the Water Testing Blog:

-- We recently head from 'JL' who asked, "What us the difference between low range quick test and quick test for well water for arsenic? What do you suggest I use for my well water. I have used the quick test before but do not know the difference." G...... 10/09/2018 | read the full article
  -- Earlier this week 'Justy' asked, "Our water got tested by a guy trying to sell us a water filtration system for our home and he did a bunch of tests.  One test showed we had way too much chlorine he said and is that true?  The number he re...... 09/07/2018 | read the full article
  -- Earlier today we received an email from 'Irma' asking, "I see your small test kits have only 5 tests.  We want to do a neighborhood wide testing program but getting it all done will take a while.  Does the 100-test version have shelf-life lon...... 09/07/2018 | read the full article
  -- This morning we received an email from 'Mandy' asking, " We had our water tested recently and the results said we have MTBE in our water.  We have well water and do not know where it came from.  Where DID it come from?" Thank you, ...... 06/27/2018 | read the full article
  -- The other day we heard from 'Thelma D' who asked, " Does a rotten egg smell in our water make it unsafe to drink?" As a general rule, when water sample has a rotten egg smell to it the odor comes from dissolved  hydrogen sulfide gas... wh...... 05/23/2018 | read the full article


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