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 Test for Oxidizers... 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. 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 Test for Oxidizers... 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. 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.

Water Testing and Water Quality Information... 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:    Who Do I Contact for Well Water Testing? -- Most ‘health’ issues stemming from contaminated well water did NOT have to happen so we really like hearing from people interested in getting their well water tested — hopefully BEFORE anyone has gotten sick from the water. National Testing Labs 97 ParameterDrinking Water Test Kit Today we heard from ‘Ilija S’ who asked, “Who do [...]... 02/22/2012 | read the full article      Arsenic Levels Found in Well Water Deemed Unsafe -- Yesterday we touched on water quality issues in California involving unsafe levels of Chromium-6, a known carcinogenic compound, in well water. Today we sadly report that the same region of the country, Coachella Valley, California, also has troubles with higher than desired concentrations of arsenic in well water. In addition to high levels of chromium-6 [...]... 02/20/2012 | read the full article      Chromium in Well Water a Reality in California -- We continually find articles these days that report about well water test samples containing unwanted heavy metal contaminants such as Chromium-6… and yet many private well owners still won’t get their own water tested on a regular basis. Today’s Chromium-6 well water finding comes to us from the Coachella Valley region of California known and [...]... 02/19/2012 | read the full article      Where Did the Arsenic (in Juice) Come From? -- Many people have asked us about the recent study that found higher than expected — and desirable — levels of arsenic in popular brands of juice… but not very many people have asked the question that weighs heavily in OUR minds: Where did the arsenic COME from? Thus far we suspect that either water used [...]... 02/10/2012 | read the full article      Kansas Residents Concerned About Bad Smelling Well Water -- Pentek US-1500 Water Filter SystemNSF/ANSI STANDARD 053 for VOC Reduction Many people believe well water cannot become tainted by contaminants because it typically comes from locations far beneath the surface. Water Testing Blog strongly suggests that you DO NOT BUY INTO THAT LINE OF THOUGHT. We ‘yelled’ that last bit for a reason. Unwanted and [...]... 02/01/2012 | read the full article   More Entries From WaterTestingBlog.Com