While the average person does not have a need to for chlorine levels much above 3 to 5 parts per million, and even then they would typically only need to do so to make sure their swimming pools had a sufficient amount of free chlorine, but other folks have the need to test for free chlorine levels in excess of 25 or 50 parts per million on a regular basis. Below we will list a few of the places where you might expect to see a need for high range free chlorine testing.

Fruit & Vegetable Processing

After fresh produce leaves the fields it travels to a processing facility where it typically gets washed with a solution containing some sort of sanitizer such as chlorine, ozone, etc. In cases where the produce processing plant uses chlorine employees must make sure the rinse water contains a certain amount of free chlorine after it has passed over the fruit/vegetables.

Levels of free chlorine drop with an increase in biological load (contamination) and the rinse water having free chlorine left after use indicates that the produce no longer contains biological contamination on its surfaces.

Childcare Facilities

State laws require that childcare facilities clean their surfaces with properly mixed sanitizing and disinfecting solutions that contain an appropriate concentration of sanitizing or disinfecting chemicals. In many cases these facilities use chlorine bleach solutions for cleaning purposes.

As a general rule these solutions must contain anywhere from 50 to 200 parts per million free chlorine for sanitizing solutions and anywhere from 500 to 800 parts per million free chlorine for disinfecting solutions. In case like this the Waterworks High Range Free Chlorine Test Strips will not work because they have an upper detection limit of only 120 parts per million free chlorine, but WaterWorks Free Chlorine Check Ultra High II has an upper detection limit of 2,000 parts per million free chlorine and works well in this application.

Some states leave it up to individual childcare facilities to determine testing frequency of sanitizing and disinfecting solutions while other states, like North Carolina for example, have strict laws dictating how often childcare facilities must perform testing.

As of January 1, 2006, all licensed, non-in-home daycare centers in the State of North Carolina had to have the ability to test the chlorine bleach content in both their sanitizing and their disinfecting solutions. Previously the law stated that they had to test only the chlorine concentration in their sanitizing solutions. ( source )

If interested in purchasing a test kit for testing sanitizing & disinfecting solutions in a childcare facility, you can find them readily available on the Filters Fast web site.

Water Lines and Water Mains

Before a water line can go into service for the first time or go back into service after a breakage or leak has gotten repaired technicians must flush (burn) the lines with water containing a high concentration of free chlorine to clean out any and biological contaminants. Typically the technicians must test the discharge water periodically until the free chlorine level remains constant at a high level for a set amount of time.

Waterworks High Range Free Chlorine Test Strips work very well for this application.

Product-specific information about Waterworks High Range Free Chlorine Test Strips:

• Testing requires just 32 seconds
• Each bottle contains 50 ready-to-use tests
• Color chart has easily distinguished color blocks at 1, 5, 10, 20, 40, 80, 120 ppm
• No harmful chemicals or reagents to handle

The other day we received a question from a reader in California who asked a question about free and total chlorine readings in what she called the ‘high range’.

I work at the front desk of a company that works on water lines and the guys are always complaining about ‘powder pillers’ and so today I finally asked what a ‘powder piller’ was. I learned two things today. One never ask a cranky engineer a question unless you know what your asking cuz they’re called POWDER PILLOWS and two the guys use them to test chlorine and they are a real pain to work with on a job. Do you have something else the guys can use cuz they REALLY don’t like those things nad they don’t test very high either it seems. Thanks for helping. MandyMandy113

A very interesting question, indeed, Mandy, and definitely one many people besides yourself probably would like to have answered — especially that cranky ‘ole engineer! He probably has spent years testing for free chlorine residual in water mains using DPD-Based test kits that require users to tear open a tiny foil packet and pour a pre-measured amount of reagent powder into a small test tube or vial.

Believe it or not, opening those small foil packets, often referred to as powder pillows, and pouring their contents into tiny openings using dirty, wet hands in cold, windy conditions really DOES take a lot of concentration and effort. Who knew, right?

So anyways, Mandy, other options do exist and they have a few bonuses they your co-workers, even the cranky ‘ole engineer, might appreciate. One option in particular even has approval by the EPA for use when testing the free chlorine residual in drinking water! See how he likes THEM apples. We think he will.

The SenSafe Free Chlorine Water Check test kit for free chlorine residuals in drinking water detects free chlorine residuals as low as 0.05 parts per million in a matter of seconds and requires the user to do nothing more than dip the strip into a sample, wait a few seconds, and compare the color on the test pad to a color chart.

Now before you say, “Oh great… a test strip…” let us remind you that the USEPA has thoroughly evaluated the SenSafe Free Chlorine Water Check test strips and found them more than adequate for testing free chlorine levels in municipal water supplies.

In the past test strips had color charts with hard to read colors, but this products stands as testament to the fact that times have changed and test strip technology has progressed quite far. See for yourself.

Many people (like several of the people here at Water Testing Blog) have difficulty telling the difference between different shades of colors with red in them so the fact that Free Chlorine Water Check uses a reagent that turns different shades of blue can really make a difference in how accurately a tester can interpret test results.

Testing higher levels of free chlorine

Since Mandy’s co-workers work on water lines, they most likely need to test for higher levels of chlorine (between 20 and 50 ppm) when flushing a new line or putting a repaired water line back in service. For testing like that they probably had to dilute samples 4 or 5 to 1 so they could get readable results with their dpd-based test kits. Not a fun task, especially since they would need to carry a supply of chlorine-free water with them to dilute their test samples.

As an alternative to diluting and testing with dpd reagents, SenSafe created a dip-n-read test strip that uses the same reagent as Free Chlorine Water Check, but has the ability to accurately detect up to 120 parts per million free chlorine w/ no monochloramine interference: WaterWorks Free Chlorine High Range.

We recently learned that the maker of SenSafe Water Test Kits has released a new version of the eXact Micro Meter Water Testing Kit that makes accurate chlorine testing with DPD-based chemistry easy for experienced testers and novices alike.

Introducing, for all your chlorine testing needs, the eXact Chlorine Photometer… a digital meter for testing chlorine that has a detection range of 0 to 11 parts per million for both free and total chlorine without the need for drop counting, crushing tablets or dissolving powders.

Using the same hardware platform as the eXact Micro 7+ Meter, this new kit comes with 100 tests for free chlorine (using DPD-1) and 100 tests for total chlorine (using DPD-4)

Aside from the 0.01 ppm resolution with +/- 0.02 ppm accuracy between 0.00 and 2.39 ppm chlorine and its high detection limit of 11 parts per million, the eXact Chlorine Photometer also offers a great deal of versatility for those who may want to test for other water quality parameters such as… Ammonia, Bromine, Chloride/Salt, Chlorine Dioxide, Chromium (in Hexavalent Form), Copper, Cyanuric Acid, Fluoride, Iodine, Iron, Low Range Total Hardness, Manganese, Nitrate, Nitrite, Ozone, Acid pH, Alkali pH, Potassium, Sulfate, Sulfide, and Turbidity.

If the need arises where you need, or want, to test for parameters other than free and total chlorine, simply pick up a bottle of the appropriate reagentstrip and follow the simple instructions in your meter’s manual.

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.

StaceyG from Rhode Island asked us a question recently:

Hi. Do chlorine test kits work for bromine, too?

Yes, Stacey, you can use a DPD-based chlorine test kit to detect bromine levels in water. Oh, and since you’ve asked about bromine, we will assume you want to test pool or hot tub water… so you can expect us to arrive shortly for the pool party.

Generally speaking, and as long as you follow the directions for testing chlorine in water using a DPD-based water test kit, you will simply have to multiply the results of the test by 2.25 if you have bromine in the water instead of chlorine.

In other words, if you got a reading of 1.0ppm chlorine, but the water actually contained bromine, you have a concentration of 2.25ppm bromine in the water.

That’s too much math for me! My brain hurts!

For those of you NOT interested in having to perform any sort of mathematical calculations poolside, many pool & spa test kits come with color charts/labels for both chlorine and bromine.

And then, for the folks who don’t want to do any math OR have to compare colors of liquids to a color chart or color comparator, we have meters such as the eXact Micro 7+ Pool/Spa Testing Meter which takes ALL the guesswork out of chlorine and bromine testing!

Last we checked, the eXact Micro 7+ Pool/Spa Testing Meter qualified for free shipping at FilterWater.Com.

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

Looking for a verstile, lightweight, waterproof water quality testing meter? Need an EPA Compliant testing meter for chlorine testing?

Introducing a new photometer using a patented method and technologies that offer faster, safer, easier, and more precise water testing.
The eXact Micro 7+ offers seven modes which provide direct read capabilities for Total Alkalinity, Bromine, Calcium Hardness, Free Chlorine, Total Chlorine, Copper, Ozone, Permanganate, pH, and % Transmission – which allows for testing of an additional 17 parameters.

The eXact Micro 7+ can measure a total of up to 26 parameters and provides EPA Compliant testing method for both Free & Total Chlorine when used with DPD chemistry.

In need of replacement reagentstrip bottles for your eXact Micro 7+ Water Quality Testing Meter?