Simply put, the total chlorine concentration in a water sample includes all available free chlorine plus all the chlorine that has already oxidized (acted on) contaminants in the water and become combined chlorine (monochloramines).

Free (available) chlorine refers to the concentration of chlorine molecules residing a water sample that have not, yet, oxidized contaminants. As a general rule you want to maintain a free chlorine residual in a body of water or water source.

Therefore, if a water sample has a total chlorine residual but no free, available chlorine, then the sample may or may not be ‘safe’. Some public (municipal) drinking water systems use only combined chlorine

Why would they do that?

It seems counter-intuitive that a public water systems would choose combined chlorine over free chlorine given free chlorine’s superior disinfecting (oxidizing) properties, but monochloramines do still have oxidizing capabilities and they do not create compounds (disinfection by-products, tri-halomethames, TTHM’s, etc.) that may cause cancer.

So… if you want to know how much free chlorine you have versus how much combined chlorine you have, simply subtract the free chlorine concentration from the total chlorine concentration:

(Total Chlorine) – (Free Chlorine) = Combined Chlorine

For pool water you can use a test strip like the Pool Check 5-Way or a Basic Taylor Test Kit to determine the free and total chlorine concentrations of a sample.

For drinking water you can use test strips like SenSafe Free Chlorine Water Check to determine the free chlorine concentration of a water sample and SenSafe Total Chlorine Water Check to determine the total chlorine concentration of a water sample.

OR, for an even easier test procedure, you can use the WaterWorks 2 Free & Total Chlorine Test Strip which tests for both free and total chlorine at the same time.

Today’s inquiry came to us from ‘Kishore’ who asked a question about a liquid test reagent that turned yellow when added to a sample of water containing chlorine-based water disinfection tablets.

Dear Sir, I mixed chlorine tablets(water purification Tablets) in water. my friend taken water in Test tube. mixed one drop of liquid then water color changed in yellow. what is name of that liquid. how to by that.please can sent details.

Hello, Kishore, and thank you for the inquiry about a liquid test reagent that turns yellow in the presence of chlorine. Based upon your description we suspect your friend used a chemical called ‘OTO’ to perform the testing. OTO stands for Orthotolidine dihydrochloride. It test for total chlorine (free chlorine plus combined chlorine collectively).

You can find OTO in most pool supply stores, as it normally comes in the more basic pool water testing kits for total chlorine and pH, the two most commonly tested pool water quality parameters.

Many companies also sell the two reagents separately since they do tend to ‘go bad’ after a year once opened and exposed to air.

If you want to perform more precise chlorine concentration testing for free chlorine, the compound most people have the most interest in (usually) when attempting to determine if water has had the proper amount of disinfectant added to it, you will want to invest in a drinking water test kit that uses DPD-based reagents. ( What is DPD? )

For an even simpler means of testing the chlorine levels in water samples you may want to consider a product such as the SenSafe Free Chlorine Water Check, an EPA Approved method for determining free chlorine concentrations in drinking water, or the WaterWorks 2 Free & Total Chlorine product that uses the same free chlorine testing method as the SenSafe Free Chlorine Water Check and also includes a separate test area for total chlorine.

Want to know more about the differences between free and total chlorine? Check out an article called Free Chlorine, Combined Chlorine, Total Chlorine.

One more thing about OTO before we go: We have heard that some countries have outlawed its use due to scientists having evidence that it may cause cancer in humans… so check local laws before making a purchase!

We hope this helps!

Anyone that has taken the initiative to install a water filter or water purification device/system in their home deserves a bit of praise… and those that continue to take an interest in the quality of their water after installing a water treatment system deserve even MORE for their efforts.

As an example, ‘J. Mampilly’ from India installed a system and now seeks to determine if he has installed the correct unit. He asked,

I would like to know about how i can confirm the effectiveness of my water purifier. Labs in India that can certify and throw light on the camparative quality of water before and after using a water purifier. Thank You

Unfortunately we do not have familiarity with water testing laboratories in India and cannot directly assist with this situation. We can suggest, however, that you contact your local health department and ask them for a list of certified water testing laboratories in your area.

Coliform Bacteria Test Kit

Before…

In order to know what type of filter or what filtering capabilities you should purchase, invest (yes, we said invest) in a thorough water analysis performed by a qualified water testing laboratory. Here, again, we suggest contacting your local board of health and asking them, for a list of certified drinking water testing labs. Alternatively, or if no labs exist in your immediate vicinity, you can use the services of accredited water testing companies such as National Testing Labs.

No matter what, though, always have your water tested BEFORE deciding on a water treatment system. Oh, and one more thing: Don’t think for one second that a salesperson doing an in-home water test has the same water testing tools or qualifications as a reputable water testing laboratory. Remember: 99% of all salespeople attempt to sell things and not accurately analyze a situation — especially if accurately diagnosing a situation could cost them a sale!

And after!

As ‘J. Mampilly’ has done, we should ALL take an interest in comparing the quality of water that comes out of our water filter systems. Only then will we know if the money we invested in (not spent on!) a quality drinking water filter system performs as expected.

Testing water quality beforehand gives us not only an idea of what we need to filter out of our water, but also a checklist of water quality parameters to monitor post-filtration. Should follow up water testing reveal that these ‘issues’ did not get corrected or suddenly show up months after the installation of a water system, perhaps the water filter has stopped working or never really worked properly in the first place and needs service of some sort.

And in conclusion…

Many people go through life ‘deaf, dumb and blind’ when it comes to the quality of their water — until an (initially) unexplainable health problem pops into their life. Then, and unfortunately sometimes too late, those same people get very interested in the quality of their water and want to punish or otherwise penalize others for allowing them to consume tainted, polluted and/or contaminated drinking water.

Although we feel much sympathy for the victims of poor quality drinking water, most of us here in the United States have the ability to at least once every great while perform basic testing for critical water quality parameters such as heavy metals (i.e. lead, mercury, copper, iron, etc.), coliform bacteria, pesticides (i.e. atrazine and simazine), chlorine levels (free and/or total), total hardness, total dissolved solids, and many others.

Many times the contaminants in a water supply will have no taste, carry no odor and not appear before the naked eye. Only testing will alert you to their presence.

Every so often we receive questions from readers who ask something along the lines of, “What do most people ask about?”

Seemed odd at first (several years ago), but after getting asked the same thing so many times we eventually came to the conclusion that a good number of people really and truly don’t know what questions they ought to have about the quality of their drinking water.

Therefore, for your reading pleasure we will now give a list of the 10 most popular topics on Water Testing Blog for the month of August (2011):

1. Free Chlorine, Total Chlorine and Combined Chlorine
    
2. Testing for Fluoride in Water
    
3. Converting Hardness: Grains per Gallon to Parts per Million
    
4. What is DPD?
    
5. Chlorine Testing: Drinking Water vs. Pool Water
    
6. Simple Chlorine Testing Meter
    
7. Dirty Pool Water Can Make You Very Sick
    
8. Testing for Chlorine in Drinking Water
    
9. Lead in Soil
    
10. Private Well Water and Natural Gas Drilling

In no way does the above list begin to scratch the surface of what curious folks read on our site, but it may help you decide what questions YOU want answered… and if you come up with a question or topic you’d like us to address, send it to us using our submit a comment/question form.

It did, however, kind of shock us that hydraulic fracturing (aka: fracking), a means of extracting natural gas from shale buried deep beneath the Earth’s surface, came in so low on the list given the amount of (bad) publicity hydraulic fracturing has received in the past few years.

We also found it somewhat odd that bacteria in water did not make a single appearance in the list but then again, most folks in the United States have city/municipal water and make the assumption that city/municipal water couldn’t ever contain something as common as bacteria — and that, friends, can sometimes become a dangerous assumption to make!

Do not let a clever sales pitch or catchy marketing jingle fool you. Many common drinking water filter systems do NOTHING to remove or reduce chloramines in water. They simply lack the technology in their filtration media to do so.

We mentioned this filter (the Pentek ChlorPlus) in the past and now feel the need to mention it again since we continue to receive inquiries from people asking why their water filters fail to remove all of the chlorine smell from their water.

The majority of water filters readily available in the marketplace do NOT remove chloramines, also known as combined chlorine. Most carbon filters remove free chlorine only. It takes a specialized type of filter like the Pentek ChlorPlus to cleanse water of unwanted chloramines.

Does my water contain chloramines?

Whether your municipal water system uses free chlorine or chloramines as its primary sanitizing agent we cannot say, but in either case your water will certainly contain chloramines. Unsure why? Take a look at this brief tutorial on free chlorine, total chlorine and combined chlorine.

That’s just a cartridge… What sort of housing does it go in?

A very keen observation followed by a very good question! The Pentek ChlorPlus filter for chloramine removal fits in most standard sized 10″ (by 2.5″) filter housings including, but not limited to, models manufactured by companies like Pentek, Ametek, US Filter, Bruner, American Plumber, Cuno, Filterite, Keystone, Water Resources and most Harmsco filter housings.

As always before purchasing a replacement cartridge for your water filter system, check, double check and TRIPLE check to make sure your housing will accommodate the filter cartridge you wish to buy!

Not a fan of chloramines in your drinking water? You now have a means of removing those pesky chloramines!

Chloramines? What are chloramines? Take a look at this earlier Water Testing Blog entry on Free Chlorine, Combined Chlorine and Total Chlorine and get a quick education on the topic!

Whether created as a byproduct of disinfection via free chlorine or the intended disinfectant in a water system, most people do NOT like the taste and odor of chloramines in their water.

Thankfully Pentek has come out with a product called the Pentek ChlorPlus 10 Chloramine Removal Water Filter Cartridge that fits in standard 10″ (x 2.5″) filter housings used in filter sytems produced by companies such as Pentek (obviously!), US Filter (recently acquired by Pentek!), Cuno, Filterite, Keystone, US Water, Water Resurces, Harmsco, and many other popular brands of water filtration systems. If your system uses a standard 10″ x 2.5″ housing, the Pentek ChlorPlus 10 ought to fit just fine!

Having said that last bit, please check the dimensions of your current filter and/or housing before ordering this product!

Looking for a 10″ replacement filter with NSF Certification? The Pentek ChlorPlus 10 uses a component tested certified to NSF Standard 42.

What does the Pentek ChlorPlus 10 remove/reduce? Using 1 micron carbon block technology this product (255416-43) should seriously reduce chloramine concentrations in drinking water and in doing so remove the (offensive) taste and odor associated with chlorine while also helping to pull out unwanted sediment, if present.

No matter how many ‘new’ and/or ‘innovative’ methods scientists devise to make water safe for drinking, we believe a certain faction in society will still put its trust in the sanitizing effects of free chlorine. This also means we believe a need for chlorine testing will always exist.

As an immediate example of this need, a Water Testing Blog reader named John recently asked, “Hi I am installing a 5000 litre water tank which i intend to add chlorine to and need an inexpensive free chlorine meter could you advise me on what to purchase as this is a new venture for me. Regards,John M.”

Thank you, John, for your question and more importantly for reminding us that we needed to examine the cost of chlorine meters at some of our favorite online merchants: FiltersFast.Com, WaterFilters.Net, FilterWater.Com, IsoPureWater.Comand Test Products.

In no particular order…

• FiltersFast.Com still carries the eXact Micro 7+ Water Testing Meter and they currently sell the basic water quality kit for $200.

  While perusing the site we noticed that FiltersFast.Com appears to carry several of the more commonly used replacement reagentstrip bottles for the eXact Micro 7+ meter: Total Alkalinity, Bromine, Calcium Hardness, Free Chlorine, Total Chlorine, Copper, Ozone, Permanganate, pH.

  eXact Micro 7+ pH Test 486639

  eXact Micro 7+ Copper Test 486632

  eXact Micro 7+ Free Chlorine 486637

  eXact Micro 7+ Total Chlorine 486670

  eXact Micro 7+ Total Alkalinity 486641

  eXact Micro 7+ Calcium Hardness 486629

  We saw no other chlorine testing meters available on the site.

• FilterWater.Com continues to carry the eXact line of water testing meters and currently has three kit versions of the eXact Micro 7+ available: Standard Water Quality for $249, Pool and Spa for $249 and Chlorine Photometer for $229.

  Each kit features the same meter, but comes with a different set of reagentstrip bottles tailored to meet the needs of a specific water testing application/market.

  In addition to the eXact Micro 7+ meter kits, we also noticed that FilterWater.Com also carries a newer eXact meter called the eXact Micro 8 Meter. That meter did not, however, appear to test for chlorine.

• WaterFilters.Net does not appear to carry any chlorine testing meters at this time.

  

• On the IsoPure Water web site we found the Extech (CL200) Exstik Direct Digital Reading Chlorine Meter for around $170.

  According to the description given, the Extech (CL200) Exstik Chlorine Meter provides only Total Chlorine results, provides results in roughly two minutes, detects as little as 0.01 ppm total chlorine, will not give erroneous results due to turbid or cloudy water, stores up to 15 readings, and has USEPA Approval for use as an acceptable method for wastewater compliance monitoring of Total Chlorine.

  We have heard very little about this meter except that it uses dpd tablets which may or may not be unique to the meter: Extech (CL203) Exstik ExTab™ Chlorine Reagent Tablets.

  

  Also on this site we saw the Oakton C301 Chlorine & pH Testing Meter which very closely resembled the second generation of the eXact meter — except in cost.

  If memory serves us correctly, the eXact meters cost around $250 or $300 when they first came out and the Oakton C301 Chlorine & pH Testing Meter costs around $530. We cannot, at this time, explain the price disparity.

  Perhaps if a member of Oakton’s staff stumbles across this posting they will find it in their heart to drop us a quick line and tell us what makes their meter better than the second generation eXact meter and worth the extra money?

• Last but least, we noticed a change that kind of takes us back… TestProducts.Com, one of the web sites for National Safety Products, now seems to carry only one chlorine testing meter and although the meter they carry does have quite an affordable price, we feel folks ought to read the fine print before making a purchase.

  

  National Safety Products now only carries one chlorine testing meter, and that meter costs around $20.

  What? A chlorine testing meter that costs so little?

  Apparently so, friends, but buyer beware! This description for this meter states it requires no chemicals (DPD) and also blatantly says that you will need to calibrate it using another method (i.e. another meter, test strips or a liquid test kit).

  Sorry National Safety Products, but we simply do NOT see the logic in the average person owning a chlorine testing meter that does NOT make use of established, trusted DPD chemistry. ORP (we guess that’s what this meter uses) technology has its place, sure, but usually in better controlled (i.e. professional, regulated, automated) environments than the average homeowner’s water source, well, etc.

And in conclusion…

The USEPA approves of using DPD when testing drinking water and/or wastewater for chlorine content. Therefore, we suggest you invest in a system that uses DPD for free chlorine and/or total chlorine residual testing.

EPA Compliant Meter for Free & Total Chlorine Testing
. . . When Used w/ Reliable, Trusted DPD Chemistry

Sniff test: If you smell chlorine, then your water most likely contains some amount of chlorine. To determine the exact amount, however, you will need to use other testing methods.

As a general rule, if your water has a chlorine smell to it, then you most likely have, at the very least, chloramines (combined chlorine) present. This does not, however, rule out the possibility that your water also may contain a free chlorine residual, too.

For the record, health officials and scientists agree that chlorine gas does NOT do the body any favors and in too great a quantity can cause lung and eye irritation… so we suggest not performing the ‘sniff test’ if you can help it.

Taste test: Not all water that contains chlorine will smell like a swimming pool. While combined chlorine (chloramines) has a strong odor associated with it, free chlorine does not. Therefore water that may not stink like chlorine may still possess a strong chlorine taste.

We do NOT advocate the taste test method for any reason. We mentioned it just so that we could talk about why water can lack a strong chlorine smell and yet still have a strong chlorine taste.

Chemical test kit: We know of many different test kits that the general public can use to determine the free and/or total chlorine concentrations in their drinking water.

“Wait… Did you just talk about two different types of chlorine?”

Yes, because as we discussed during a few moments ago, one can have free chlorine and/or combined chlorine in their water. Typically free chlorine acts as the main sanitizing and/or disinfecting agent in a chlorinated water supply and once the free chlorine finds an organic contaminant to ‘kill’, it becomes entangled with the contaminant and forms a combined chlorine molecule.

Therefore, it stands to reason that a chlorinated water supply may contain both free and combined chlorine at the same time if the free chlorine molecules have successfully neutralized all biological contaminants and the effort did not require the use/exhaustion of all free chlorine molecules present in the water supply.

Getting back to chemical test kits, please…

Now that we have established the existence of different types of chlorine which may or may not exist in a water supply, we will now discuss different ways of testing for chlorine in a water supply.

• Test Strips — Perfect for field testing because they require the user only to dip the strip into the water and compare the color of the test pad/area to a color chart that came with the package of test strips. Products exist for the detection of both free and total chlorine. People can even get a single test strip to test for both at the same using a product called WaterWorks 2

• ‘Wet’ Chemical Test Kits — Considered by most as the traditional, tried and true method for testing the quality of water. Most ‘wet’ kits typically require dissolving DPD as a tablet, powder or liquid into water samples and either comparing the colors of resultant solutions to color charts or adding drops of an additional chemical until a second color change reaction occurs.

  Simpler ‘wet chemistry’ test kits for chlorine (i.e. 2-way pool water test kits) use a different chemical called OTO (Orthotolidine) and detect total chlorine (free chlorine + combined chlorine = total chlorine).

  Problem w/ using OTO: No way exists to use OTO in a way that will allow a person to determine the free chlorine concentration.

  The DPD reagent system does, however, allow for differentiation between the two if a water sample has DPD-1 added first, gets analyzed, and then has DPD-3 added… and then get analyzed again.

• Water Testing Meters — Most water testing meters for chlorine (i.e. the eXact Chlorine Photometer) require the use of DPD, a chemical indicator which turns a shade of pink/red in the presence of chlorine molecules. DPD-1 indicates the presence of free chlorine and a combination of DPD-1 plus DPD-3 indicates the presence of free and/or combined chlorine (total chlorine).

So… Which method of chlorine testing will work best for you? Ask yourself the following questions:

1) Do you need to test for free chlorine, total chlorine or both?

2) How much accuracy and precision will you need in your results?

3) If performing testing for reporting purposes, what do the rules and regulations governing your profession say you must use as a testing methods?

Once you have answered those three questions you will have a clear idea of whether you should use chlorine test strips, wet chemistry test kits for chlorine testing or chlorine testing meters to determine chlorine concentrations in your water.

As the debate over the benefits and problems associated with use of free chlorine ( EPA Approved test strip for free chlorine ) as a disinfectant in public and private drinking water systems rages on and more people become aware of compounds known as disinfection byproducts, the desire for point-of-use water filtration systems capable of removing disinfection byproducts continues to grow.

One particular disinfection byproduct of, trihalomethanes (often abbreviated as THM’s or TTHM’s), has gained enough notoriety that companies like PUR have started certifying some of their products to NSF/ANSI Standards for the reduction of trihalomethanes in drinking water.

Below you will find a list of several PUR water filtration products that have tested and certified to NSF/ANSI Standard 53 (Drinking Water Treatment Units – Health Effects) for the reduction of TTHM’s and other unwanted drinking water contaminants:

• PUR CR-6000 Filtered Water Pitcher

• PUR CR-6000C Filtered Water Pitcher with LED Light

• PUR Faucet Mount Filter 3-Stage – Flavor Options

• PUR Faucet Mount Filter 3-Stage Horizontal Chrome

• PUR Faucet Mount Filter System 3-Stage Chrome

• PUR Faucet Mount Filter System 2-Stage White

For those unfamiliar with how trihalomethanes get into drinking water, they get created when free chlorine molecules attack, neutralize and become entangled with a biological contaminant. That process chain of events converts free chlorine into combined chlorine and in the process disinfection byproducts get created.

What harm can trihalomethanes in drinking water cause?

Four different trihalomethanes can form as a result of chlorination: Chloroform, Bromodichloromethane, Dibromochloromethane, and Bromoform. The United States Environmental Protection has found that excessive exposure to these compounds has resulted laboratory rats developing cancer.

While many scientists may disagree on the exactly how much exposure to each compound constitutes overexposure, we think it wise to keep tabs on your local water treatment system’s track record of trihalomethane level management (data available in annual reports) and if deemed necessary, install an NSF certified water treatment system capable of reducing trhalomethane levels.

We get questions about chlorine all the time. Usually people want to know if their water has any chlorine in it, how much chlorine it contains, how they can reduce the chlorine in their water, why their water has chlorine in it, and if the chlorine in their water poses a health risk.

Today’s ‘question’ hits a lot of those same points in a new, and somewhat confusing manner. It comes from TamTom18894: “Our shower water contains a lot of chlorine and we think it too high. Yes?”

Not sure how TamTom thinks we will figure out the answer to their question since we have no interest in going to their home and testing their shower water… so we will, instead, discuss simple ways to test chlorine levels in tap water so they can figure out the answer on their own… and then list a few ways to reduce the levels of chlorine that they find.

First, test the water for chlorine residual. The simplest method we know of requires very little time and tests for both free and total chlorine at the same time. The WaterWorks 2 Free & Total Chlorine Test Kit provides fast, dependable results for both free and total chlorine concentrations in water within a minute.

For those who prefer a more ‘traditional’ method, such as a wet kit that uses DPD as its reagent, you probably either already have a kit you can use or you know where you can get one… but did you know an easier method of getting the DPD into your 10 mL sample exists?

If not, then you really ought to check out the DPD-1 ReagentStrip Delivery System which adds a precise dose of DPD-1 to a 10 mL sample without the need for crushing tablets, working with hard-to-open powder pillows or counting drops of messy liquids.

For more precise results, some people turn to meters such as the eXact Chlorine Photometer which can test both free and total chlorine concentrations from 0 to 11 ppm w/ no tablets to crush, drops to count, or powders to mix.

Once you know how much chlorine you have in your water, and what variety of chlorine you have in your water, you can then set about the task of selecting a water filtration device that will best address your individual water quality needs.

Removing free chlorine from shower water

The easiest way involves adding an inline shower filter such as the Sprite High Output Shower Filter which you place behind your existing shower head. It removes: 98.9% of free chlorine, rust from water, sulfur smell, and bad odors. Additionally, it reduces iron oxide, chlorine vapors, and scale build-up on shower surfaces.

Don’t already have a shower head? Need an excuse to get rid of your existing shower head? You can get the same NSF / ANSI 177 Certified shower filter pre-fitted with a good looking, 2.5 GPM shower head. The Sprite High Output Shower Filter (-A) comes in three finishes (brushed nickel, chrome and polished brass).

Removing combined chlorine (chloramines) from shower water

Many devices will claim to remove combined chlorine, total chlorine and/or chloramines. We want you know that in our experience (thus far) we have yet to come across a shower filter that will perform that task. Inline shower filers simply do not have the required amount of filtration media required to do a good job removing chloramines from shower water.

Chloramines have a high amount of chemical stability and as such require special consideration when attempting to remove them. Typically a device capable of effectively reducing chloramines (combined chlorine) levels in drinking water will have a relatively large media bed of Granular Activated Carbon (GAC) and/or a specialized ion-exchange resin.

Larger media beds mean more time in contact with the filtration media intended to remove the chloramines.

We have rumors of ‘catalytic granular activated carbon’ (cGAC) but have not, as of yet, learned enough about it to discuss its merits and/or shortcomings.