Whether you need a basic test kit for chlorine & pH, a set of easy-to-use chlorine test strips, or an electronic chlorine testing meter, you will find the product to suit your testing needs on ChlorineTests.Com.

You can also find replacement reagents for several different chlorine test kits on ChlorineTests.Com, which naturally means you will find DPD tablets on the site for sure.

And now for a few basic chlorine testing facts:

• Test kits containing only OTO as their chlorine testing reagent will test for total chlorine only.

• Free chlorine testing requires DPD-1. Adding DPD-3 to the sample after adding DPD-1 allows a person to test for total chlorine.

• The USEPA has set the maximum contaminant level for chlorine in drinking water at 4.0ppm. This limit applies to both free chlorine levels and total chlorine levels.

• When testing for parameters other than chlorine, some test kits will require the use of chlorine eliminating agents such as sodium thiosulfate before testing can take place.

• Water containing the same amount of total chlorine as it does has very little or no free chlorine.

• The difference between the free chlorine level and the total chlorine level equals the chloramine concentration.

With so many news stories surfacing about pool water and/or drinking water not having adequate disinfectant levels many health officials have started pushing for increased testing and they don’t mean testing for chlorine residuals with test strips or liquid test kits which both require testers to match colors to get readings.

Rather than trust test personnel to use established methods of chlorine testing such as the Taylor FAS DPD Test Kit and/or the recently EPA Approved SenSafe Free Chlorine Water Check product, some folks want to remove as much subjectivity from the chlorine testing process as possible… and that means using meters to test chlorine residuals.

One example of a meter that some folks have turned to goes by the name of Extech (CL200) Exstik Direct Digital Reading Chlorine Meter and you can see a picture of that meter to the left.

The Extech CL200 Chlorine Testing Meter tests only for TOTAL chlorine, uses DPD as its reagent, requires roughly 2 minutes for testing, stores up to 15 readings internally, and detects total chlorine levels down to 0.01ppm (mg/L).

Extech, the manufacturer, claims the EPA has deemed the meter, with its associated DPD testing method, acceptable for wastewater compliance monitoring of Total Chlorine.

From what we can see on the IsoPureWater web site, this meter cannot used generic DPD tablets, DPD powder pillows, or DPD liquids designed for 10 mL sample sizes… and that means having fewer shopping options when the time comes to acquire replacement DPD reagents.

Not necessarily a show-stopper by any stretch of the imagination since a pack of 100 DPD reagent tablets for this meter costs under $30.

Definitely keep this meter in mind should you need a fast, compact meter for testing total chlorine levels in water.

A plethora of health-related problems afflict many people living in Africa and many of those health conditions stem from the fact that the continent lacks an infrastructure capable of delivering clean, safe drinking water to many of its residents.

With that in mind, please excuse our departure from the normal subject matter and indulge us as we answer a question about purchasing DPD test tablets for chlorine testing in Zambia, an African Nation.

“Robert K” asked…

I need to know if there is company in Zambia or Sub-sahara Africa selling DPD #1 tablets.

This is a very informative site, keep it up

Thank you, Robert, for contacting Water Testing Blog with this question. We don’t know a whole lot about companies doing business with other areas of the world such as Zambia, but we did find a few links that may prove useful information.

• http://www.wisa.org.za/Home/Home.htm — Water Institute of Southern Africa

• http://www.smianalytical.co.za/water-analysis.html– SMI Analytical Services Provides Water Testing Services to South Africa

• http://www.merck-chemicals.co.za/contact — Contact Merck Chemicals (Zambia Office)

• http://www.mobilis.co.za/ — Imports Pool Chemicals & Testing Supplies Into Africa

Sorry we cannot provide more assistance than we have, but we do hope one of the links above will point you in a useful direction.

For those interested in learning more about DPD and its uses, please check out an earlier posting entitled What is DPD?.

If you would like to purchase DPD from a retailer/distributor in the US, the following links will take you to a site where you can order DPD #1 and/or DPD #3 in packs of 100 and packs of 1,000.

While many companies have moved away from single parameter water testing meters and now produce meters that can test for a number of parameters instead of just one, Hanna recently released its new Hanna Checker HC Photometer for Free Chlorine which tests exclusively for free chlorine using EPA Approved DPD-1 as its reagent.

Specifications for the Hanna Checker HC Photometer for Free Chlorine:

• Detection Range: 0.00 to 2.50 ppm (mg/L)
• Resolution: 0.01 ppm (mg/L)
• Precision: ±0.03 ppm (mg/L) @ 25°C
• Power Source: (1) 1.5 Volt AAA Battery
• Light Source: 525 nm LED
• Sample Size: 10mL
• Applicable Testing Method: Adaptation of the EPA approved DPD method Standard Method 4500-ClG

Does the Hanna Checker HC Photometer for Free Chlorine use DPD?

We already answered this one, but yes, it does. The Hanna Checker HC Photometer for Free Chlorine uses an adaptation of the EPA approved DPD method Standard Method 4500-ClG. Given that the test uses a standard 10mL sample, we would guess that the meter can use any standard DPD reagents for a 10mL sample size.

Our opinion of the meter?

• Many of us here at Water Testing Blog have large hands with clumsy fingers so meters like this one that still use cuvettes, and GLASS cuvettes at that, kind of scare us. On top of that, most pool areas prohibit the use of glass in the pool area and many food processing facilities do as well.

• The meter appears to use pouches of powder which get ripped open prior to use… and we see people accidentally spilling the DPD powder and/or having trouble pouring the powder into the little cuvette — especially if testing outdoors in a breezy climate like one might find poolside.

• Having said all that, we DO, however, think that Hanna hit a nice price point w/ this meter; not too expensive and not too inexpensive.

• Hanna MISSED the mark w/ its pricing for the DPD-1 reagents. Each test will cost nearly $0.40 to run… when other testing methods use DPD-1 reagents (i.e. DPD tablets) that cost less than $0.10 per test.

Janet wrote in and asked…

I need to buy Dpd Tablets and I have not found a supplier nor a Manufacturer to buy from.

Kindly Link me with Dpd Tablets Manufacturers who can supply me.

We thank you very much, Janet, for your inquiry and suggest you take a look at the material below, as it will lead you to what you seek:

For those of you interested in learning more about DPD and its uses, please refer to an earlier posting entitled What id DPD?.

National Stock Number (NSN) for “Chlorine Test Tablet” — 6550012191061 and 6550014257957

We recently received a number of request from Water Testing Blog readers to post a list of popular water quality topics so that they could keep tabs on ‘hot topics’ more easily. Not wanting to disappoint, we have decided to do this on a semi-regular basis.

Below you will find the most popular Water Testing Blog entries for the month of July 2009:

• Free Chlorine and Total Chlorine: In this chlorine-related water quality blog posting we discussed why some chlorine testing products such as Pool Check Test Strips work exceptionally well for swimming pools and spas, but do not offer the correct chlorine detection levels required for drinking water.

• Free, Total & Combined Chlorine: In this chlorine-related water quality testing blog entry we dicussed the differences between free chlorine, total chlorine, and combine chlorine as well as methods to test for each one.

• Dirty Pool Water Can Make You Sick: The title pretty mucha says it all. Just as with drinking water, failing to test pool water can allow dangerous forms of bacteria to grow, flourish, and possibly make a person sick. Remember: 1 in 5 American Adults Admits to Peeing in the Pool. Yuck!

• www.pool-water-test-kits.com: In this posting we brought this pool water test kits to your attention. It’s a fast, easy way to find the pool/spa testing supplies you need to keep your water crystal clear, safe, and enjoyable.

• Free Water Hardness Test Strips: Here we pointed people to Morton Salt Company and Diamond Salt Company web sites where they could order free water hardness test strips.

• DPD Tablets for Chlorine Testing: We always stress the importance of accurate chlorine testing and in this post we provided links to a web site where readers could find replacement DPD tablets and replacement DPD powder for their chlorine/bromine test kits.

• Water Filters for Hikers & Campers: For all those who enjoy going for long walks in the woods, camping in the mountains, mountain biking, or just having clean, safe drinking water to drink when away from home, we provided links to personal water filtration devices and systems from the Katadyne Company.

• Hardness Grains per Gallon vs. Parts per Million: Once again, the name says it all. What more can we say about this posting dealing with water hardness measurement scales.

• Chlorine Filters for Garden Hoses: One would think people already know that the same chlorinated water they filter in their homes goes in their gardens, too, but apparently not… so we provided links to water filters for garden hoses.

• www.pool-water-testing.com: Here we simply brought a site dedicated to testing pool water to the spotlight. Not much more to say really… other than go test your pool often!

With temperatures soaring to record and near record highs all across the United States, it comes as no surprise to us that we have received numerous questions pertaining to the proper treatment of green swimming pool water, smelly swimming pool water… and some water that would make the average sewer worker vomit.

Therefore we have located yet another online source for Pool Water Testing and Pool Chemical Supplies. Below you will find quick links to various pool testing supplies, pool chemicals, pool shock treatments and other items such as automatic chemical feeders for swimming pools.

Just as with your drinking water, though, nothing beats a professional water test if you have reason to suspect that harmful bacteria or harmful levels of contaminants have entered your pool water.

With all the posts we’ve written about the importance of testing chlorine levels in drinking water, we seem to have forgotten that a lot of people have test kits already and simply need replacement dpd tablets. The links below will take you to a site where you can pick up replacement dpd tablets and DPD powder for the Taylor brand of water test kits for pools and spas.

Several members of the Water Testing Blog staff have spoken with members of the military, both currently enlisted and recently discharged, and found out that some soldiers do not have access to simple, efficient tools they can use to test potential drinking water while deployed in foreign countries.

In most cases they carry packets of sanitizing/disinfecting tablets which they can use to put into their canteens to kill off bacteria, but what about lead, arsenic, cyanide and other items which can EASILY render an entire unit inoperable and take them away from their assigned duties?

Thankfully US Army, Navy, Air Force, and Marine Corps medical units deployed around the globe now have the ability to make use of simple water quality test kits which give them the ability to read basic water quality parameters quickly and easily.

Arsenic in Water and Soil: Arsenic Quick^TM

Bacteria in Water: Bacteria Check

Chlorine Residual (Free): SenSafe^TM Free Chlorine Water Check

Chlorine Residual (Total): SenSafe^TM Total Chlorine Water Check

Cyanide in Water: Cyanide ReagentStrip^TM

DPD-1 and DPD-4 (Chlorine Testing): eXact DPD ReagentStrips^TM

Lead in Water: Lead in Water Test Kit

Multi Parameter (6 Parameters): Well Water Check

Multi Parameter (11 Parameters): Well Driller Standard Water Test Kit

Multi Parameter (13 Parameters): COMPLETE Water Test Kit

Multi Parameter (15 Parameters): Water Quality Test Kit

Most of us know how badly we feel after ‘a night on the town’ filled with margaritas, martinis, cocktails and body shots because of dehydration. Now try to imagine how our soldiers must feel after a few MONTHS in the desert wearing full combat gear.

Safe drinking water means safer soldiers.

One of the most widely used testing methods for free and total chlorine makes use of something known as ‘DPD’ which stands for N,N Diethyl-1,4 Phenylenediamine Sulfate. 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.

At low oxidizer concentrations water samples turn a slight shade of pink in the presence of DPD and at higher oxidizer concentrations the sample will turn blood-red orange. In extremely high concentrations of oxidizers, as in above 10 ppm, the sample will turn blood-red and then go crystal clear due to the bleaching effect of the oxidizer(s) it contains.

Other oxidizers such as ozone and total chlorine do not react directly with DPD and require the addition of a compound known as Potassium Iodide (KI) before they will react with DPD.

• DPD-1 — Used to test oxidizer levels in water samples containing free chlorine, bromine, iodine, chlorine dioxide and/or permanganate.
• DPD-3 — Useless on its own, but when added to samples already containing DPD-1 and free chlorine, total chlorine, bromine, iodine, chlorine dioxide, permanganate and/or ozone, pink through blood-red color development will occur in the sample.
• DPD-4 — The combination of DPD-1 (N,N Diethyl-1,4 Phenylenediamine Sulfate) and DPD-3 (KI) to samples containing free chlorine, total chlorine, bromine, iodine, chlorine dioxide, permanganate and/or ozone will result in pink through blood-red color development in the sample. Simply put, DPD-1 + DPD-3 = DPD-4.

DPD comes in various forms, the most common of which include tablets, powder pillows, liquids and ReagentStrips^TM. Each works equally well when used correctly and may typically be interchanged with one another, though all do have their pros and cons.

• Tablets: One of the cheapest forms of DPD available and has a very long shelf-life. Difficult to break apart and dissolve in cold or hard water samples and may leave suspended solids floating around in samples.
• Powder Pillows: Inexpensive form of DPD. Difficult to dissolve in cold or hard water samples and may leave suspended solids floating around in samples. Users also complain of ‘annoyance value’ associated with having to tear the foil pillows open and pour the DPD powder into the sample vials. Not well-suited for outdoor testing.
• Liquids: Shorter shelf-life and much more unstable than other forms of DPD, considered ‘messy’ by many users, but also probably the expensive form of DPD.
• ReagentStrips^TM: Convenient delivery method for DPD, rarely leaves undissolved solids in samples regardless of temperature or hardness, decent shelf-life, and available in bottles of 50 or individually wrapped tests (excellent for field work).

While many test protocols call only for a visual verification of chlorine levels in water determined through the use of DPD testing methods, many others require the use of a digital chlorine analyzer and DPD testing methods. Below please find an EPA Compliant meter which make use of DPD chemistry for chlorine concentration determination:

• eXact Micro 7+ Water Quality Testing Meter — EPA Compliant for free and total chlorine when used in conjunction with a DPD-based reagent system.  Handheld multi-parameter water quality testing meter.  IP67 waterproof rating and the unit floats. Made from recyclable parts and uses 60% less reagent than devices using 10 mL samples.

Update — Got a chlorine test kit/meter that has a 10 mL sample size and uses DPD-1 tablets, powders or liquids? If so, then you definitely want to check out DPD-1 ReagentStrips for free chlorine. They mix into solution much quicker, easier and cleanly than DPD powders and DPD tablets and have a much longer shelf life than DPD liquids.

The USEPA has accepted DPD-1 ReagentStrips for reporting water and wastewater analysis. That means the USEPA has found the DPD-1 ReagentStrip free chlorine testing procedure equivalent to its own USEPA method 330.5 for wastewater and Standard Method 4500-Cl G for drinking water when used with Palintest Chlorometer 1000 or equivalent.

Update — Want to use less water when testing for free (and total) chlorine? The eXact Chlorine Photometer requires 60% less test sample and meets the criteria for a USEPA Compliant Meter for free and total chlorine testing.