Although both manufactured by Industrial Test Systems, Inc., a US based company in South Carolina, the DPD-1 ReagentStrip and SenSafe Free Chlorine Water Check products test for free chlorine residual in very different ways.

The chart below will explain the differences and similarities between the two free chlorine residual test methods:

	DPD-1 ReagentStrips™	SenSafe™ Free Chlorine Water Check
Detects:	Free Chlorine Residual (and Other Oxidizers Normally Tested Using DPD-1 Chemistry)	Free Chlorine Residual
Test Procedure Overview:	Liberarting of DPD-1 Reagents Off Reagent Pads Into 10mL Sample and Checking Chlorine Concentration Visually by Color Comparator or Electronically Using a Colorimeter	Immersion of Test Strip in Water Sample, Removal of Test Strip After Specified Period of Time, and Visual Comparison of Developed Color in Test Area to a Color Chart
Detection Range:	0-6ppm	0-6ppm
Accuracy & Precision:	Depends on the Method Used to Interpret the Developed Color in the 10mL Sample. Visual Methods Will Have Less Precision Than Meters	0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.2, 1.5, 2, 2.6, 4, 6 ppm (mg/L)
Certifications & Compliance:	DPD Testing as Specified in 4500-CL G Check w/ Your Local Health Department for Final Word on Compliance	USEPA Approved Test Method for Free Chlorine Read the EPA Letter   View EPA Approved methods   Check w/ Your Local Health Department for Final Word on Compliance
Number of Tests:	100 Tests per Package	50 Tests per Package
Benefits:	Cleaner to Use Than DPD-1 Powders (i.e. DPD-1 Powder Pillows)   Dissolves Easier Than DPD-1 Tablets   Longer Shelf-Life Than DPD Liquid Reagents   No Undissolved Solids When Testing in Cold Water (5ºC)   Requires No MSDS	Safe for Use on Most Production Floors   Requires No Specialized Testing Knowledge   No Expensive Meter (Colorimeter)   Designed to Resist Monochloramine Interference   Requires No MSDS
Per Unit Cost:	$15.99 per Package of 100 Tests	$15.99 per Bottle of 50 Tests

As always, if monitoring free chlorine residual for reporting and/or compliance monitoring we suggest contacting your local health inspector before switching to a different chlorine testing method.

Although seemingly counter-intuitive, many methods approved on a Federal level may not have attained acceptance, yet, on a State or Local level.

In the water business testing for free chlorine happens quite frequently (as Scott just said)… and we know of two ways to make that task easier:

• DPD ReagentStrips — If you use DPD-1 to test for free chlorine residual, then undoubtedly you do so using DPD in powder or tablet form. Both methods work, but DPD-1 ReagentStrips make testing for free chlorine residual in water a faster and easier process while staying in compliance with 4500-CL G. Simply insert a DPD-1 ReagentStrip into a 10mL water sample, move it back and forth (liberated required DPD chemistry off of reagent pads), and read visually or with your favorite meter.
   
• SenSafe™ Free Chlorine Water Check — In the original recommendation letter from the USEPA, dated October 2003: “We believe that the ITS test strips will provide the regulatory community with a valuable option for monitoring free chlorine levels in drinking water.” This method bears USEPA Approval for in drinking water applications.

While both testing methods make free chlorine residual testing much easier without losing accuracy, we highly suggest check with your State and Local inspectors first before using either product for compliance monitoring… because as you know (probably better than we do!), sometimes State/Local regulation changes do not always keep up with Federal Regulation changes.

Ann asked, “Hi. I work in the food and beverage industry and our our most recent health inspector told us we need to have a way to test for 800ppm or greater free chlorine residual in our washing solutions. Do you carry anything for that? I saw the ones that go up to 120ppm but I need higher. Thanks.”

Well, Ann, we do actually carry a product for testing higher concentrations of free chlorine in water: Free Chlorine Check Ultra High Range II tests up to 2,000ppm free chlorine and does so in about a minute.

Below you will find the color chart for the :

Color Chart for Free Chlorine Check Ultra High Range II

As you can see, this high range free chlorine test strip product has a low detection level of 25ppm and a high detection level of 2,000ppm.

What’s the deal w/ the sanitizing & disinfection solution labels?

The manufacturer’s of this product, Industrial Test Systems, originally created this product to meet a need in North Carolina. Because of several unfortunate incidents where young children in daycare and childcare facilities came in contact with disinfecting and/or sanitizing solutions mixed way too strong, laws were enacted that required licensed daycare and childcare facilities in North Carolina to test the concentrations of their ‘bleach water’ on a daily basis.

Childcare and daycare facilities in North Carolina have authorization to use the Free Chlorine Check Ultra High Range II test strip product for the purpose of testing disinfecting and sanitizing solutions.

Note: Different states have different laws governing what constitutes a properly mixed sanitizing or disinfecting solution and different industries will also have different requirements. Check with your local health department or health inspector before deciding on the concentrations you will use!

Looking for the “The Childcare Kit – Part No: 480124-3K” ?

If so, then you already know it includes the following…

• (3) Bottles of 100 Tests… for a Total of 300 Tests
• (1) Tablespoon Measuring Tool
• (1) 1/4 Cup Measuring Tool
• (1) Sanitizer Preparation Method

… and you can purchase The Childcare Kit – Part No: 480124-3K in the Water Test Kit Store.

‘TomToo’ very recently — as in a few minutes ago — asked about chlorine testing and which chlorine test he should use:

“Saw your chlorine sale announcement and have a question. The water in our beach house stinks really bad of chlorine when we first get there and we want to test to make sure it’s safe to use but you have free and total chlorine strips. How do you know which to use?”

Thanks for your inquiry, TomToo, and believe us when we say others share your confusion when it comes to knowing which type of chlorine they need to test for.

Lucky for you, though, we have simple answer if your concern deals only with worrying about having too much chlorine in the water. You should test for total chlorine.

The USEPA set the Maximum Contaminant Level for chlorine in drinking water at 4 ppm (parts per million) and that number takes into account ALL of the chlorine in a water sample, meaning both free and combined chlorine.

Moral of the story?

If you need to know the FULL amount of chlorine in a drinking water sample, testing for total chlorine makes the most sense.

Whether testing drinking water at home, process water used in an industrial application, or wastewater for its chlorine before discharge into the environment, we feel quite certain that at least one of the chlorine test strip products above will come in handy — and this weekend you can save money when buying them!

As always, if you have any questions, please do not hesitate to ask! You may reach us easily using our Contact Us Form…. and yes we work on the weekends. 🙂

Have a great weekend, everyone, and don’t forget to stay hydrated!

may sound dumb but I have just purchased a hot tub and these strips came with it, I
am not understanding the difference between total chlorine and free chlorine my test
shows 0 on both the rest of my colors are good what do I need to add? thanks

Believe it or not, Sally, we actually COMMEND you for having the courage to ask the question that you did… because too many people don’t ask questions and wind up with potentially unsafe water conditions!

For a tutorial on the differences between free and total chlorine we suggest you take a look at a popular blog entry on our site called “What is the Difference Between Total Residual Chlorine and Free Chlorine?“.

In a nutshell, however, if you use chlorine or bromine to sanitize your hot tub water then you have a problem that needs remedying right away: Your water contains no sanitizers — and you need to add some right away!

If, on the other hand, you use an alternative water sanitizing system (mineral ionization, ozone, peroxide, biguanide, etc.), then having no chlorine reading on either pad probably isn’t an issue.

Testing for alternative sanitizers

As more and more folks migrate towards alternative sanitizing systems for their spas and hot tubs, the need for testing methods for the alternative sanitizing methods grows.

Thankfully some methods, like the WaterWorks Peroxide Test Strips and the SenSafe Ozone Check, already exist.

And now for something completely (maybe) different…

Always consider the source water FIRST

Whether you have a swimming pool or a hot tub, the final quality of your water will depend heavily upon the quality of your source water (the water you fill your pool or hot tub with) and, more importantly, what you do to correct any issues that may exist with the water once you have added it to your pool or spa.

As ‘coders’ in the computer programming world often say, ‘Garbage In, Garbage Out!’

If your source water sucks, to use a term most of us definitely recognize, then without correction the water quality of any pool or spa filled with the source water will also suck.

Testing the water prior to the addition of chemicals makes total sense — unless, of course, you would rather spend money to fix problems like… staining on liners, fixtures, etc. caused by the addition of sanitizers (chlorine, bromine, etc.) which NEED to get added to the water.

Important Chemistry Lesson: Adding strong oxidizers like chlorine to water that contains dissolved metals like copper, iron, etc. may result in the formation of insoluble compounds that will settle on and stain any surfaces they encounter.

“For the last 8 years we lived in the country and had our own well and some pretty good tasting water. Recently we had to move (regrettably!) closer to our jobs in order to save on gas and so the kids could go to better schools. We THOUGHT the water would taste better since it got treated by the city where we moved but it tastes something awful like pool water only worse. Is that normal and can we do anything about it? Hoping for good news ! Thanks!”

The above inquiry came from ‘Diane’ and to answer her questions directly, “Maybe & Yes!”

By law public water systems must treat water for unwanted biological contaminants and for the most part pretty much all of them use some form of chlorine as part of their disinfection process. Also by law, water may not leave their facilities containing more than 4 ppm (parts per million) free and/or total chlorine.

Want more information on the difference between free and total chlorine? Take a look at an earlier article entitled Free Chlorine, Combined Chlorine and Total Chlorine.

Getting back to Diane’s question, though, a water supply could very well contain under the allowed level of free and/or total chlorine — and still smell and taste really bad.

Getting rid of chlorine taste and smell

For most folks removing the chlorine taste and odor from their drinking water begins and ends with the installation of a Granular Activated Carbon (GAC) filter as a countertop water filter, faucet filter, undersink water filter, or whole house water filtration device.

For others, however, the reduction and/or removal of chlorine taste and odor requires the installation of a granular activated carbon water filter as well as a more sophisticated water filter like a reverse osmosis water filter that more or less strips EVERYthing out of water… and for that level of filtration one typically will need to spend a few extra dollars.

Two main types of chlorine to test for?

In order to determine which water filter will best address your chlorine in drinking water reduction/removal needs you will first need to determine whether your water supplier uses free chlorine or chloramines as its main disinfectant. For that task we have found that the WaterWorks 2 Free & Total Chlorine Test Strips works quite well since it tests for both free and total chlorine at the same time.

Upon completion of testing, simply subtract the free chlorine reading from the total chlorine reading to get the chloramine concentration. If you obtain a value the same as, or very close to, the total concentration (i.e. the free chlorine test pad reads zero) then your water supplier more than likely uses a process known as chloramination as it primary disinfecting method — and you will need a more sophisticated filtration system to get rid of the chlorine taste and odor.

An ex-employee at an asphalt company has come forward recently with allegations that higher-ups in the company encouraged him to submit fake water samples (taken from a rainwater collection bucket) and submit them for testing by the Oregon Department of Transportation… because the higher-ups feared actual testing of their waste water stream would reveal code violations.

Nothing makes the taste of fresh, clean drinking water vanish quite like… runoff from an asphalt plant, right? Even just saying that to ourselves as we put together this blog posting turned our stomachs.

So, if unlike ourselves you actually believe all of required environmental testing gets done in the proper manner, perhaps now you will see things a bit differently and start testing your water on, at the very least, a semi-regular basis?

Think we made up this story? Not! Read the source article here.

Common water contaminants to test for?

Although far more sinister compounds and elements exist in our world that could enter our water supply (i.e. organic solvents, radioactive isotopes, etc.), we routinely suggest testing for heavy metals as a good starting point because whether you have city/municipal water or your water comes from a well or spring, metals can pretty much always — under the right circumstances — find a way into the water supply.

• Well casings typically get made out of metal.

• City/Municipal water must travel through miles of metal piping before it gets to one’s residence.

• Water extracted from wells comes in contact with rocks and soil that all contain traces of metals.

• While most homes these days contain plastic plumbing, many older homes still contain metallic plumbing (copper w/ lead-laced solder at the joints) plumbing… and metal lines get used to connect most homes (regardless of age) to the municipal water system.

What should I test for next?

After dissolved metals in water testing things get a bit murky. Pardon the expression.

Folks with well water may want to test for all sorts of things such as nitrates, nitrites, coliform bacteria (important!), hydrogen sulfide, arsenic, etc. while folks on city water may want to test for specific metals such as copper and lead, total hardness, free chlorine, total chlorine, etc.

No matter what type of water you have going into your home, school or place of business, only regular testing of the water’s quality will let you know if you have anything to worry about when it comes to the safety and purity of the water you drink.

Good afternoon, Domingo, and thank you for your inquiry regarding possibly providing water testing to airlines and ground services at an airport in the Bahamas.

At this point we do not know exactly what sort of information you seek… but we have heard that some airlines already have guidelines and procedures in place which require testing of water that will get served on their planes regardless of geographic location.

At the very minimum those tests, we would guess, include testing water in planes’ potable water tanks for free chlorine levels and unwanted organic contaminants such as coliform bacteria — though the results of bacteria testing would not become known until after 24 hours and by that time the plane would obviously have already left the ground and traveled, perhaps halfway around the globe.

We suspect that you will need to get in touch with each respective airline’s main office if you want to learn more about what each airline tests for. Additionally, you may also want to contact the FAA (Federal Aviation Administration in the United States) to see if they have any regulations on the books governing water quality on airplanes and/or at airports.

Conveniently, this brings us to the matter of testing water used by ground services at the airport.

Without a doubt any food service operation must adhere to water quality requirements and testing testing requirements spelled out for them by the local health department.

Also without a doubt, the airport answers to the region’s environmental and/or natural resources department on matters dealing with the quality of water exiting the property in the form of waste water, runoff, etc.

Sorry we do not have more information to share on the topic of airport water testing but we do think, after hearing rumors involving accidental fuel spills (unreported), deicing solution spills (unreported), and the detection of coliform bacteria in potable water supplies on commercial aircraft, etc., that the topic deserves more attention than perhaps many people give it.

We wish you the best of luck in getting your business off the ground!

Pun intended. 😉

Thanks for the question, Mandy!

When a person tells us they have no chlorine reading on their test kit usually one or more of the following factors has played a part in causing that to happen:

• Chlorine demand greater than chemical feeder system can supply
• Old or expired test kit reagents, test strips, etc. not properly reading chlorine levels
• Lack of pool stabilizer (cyanuric acid)

The fact that you can smell chlorine, however, tells us that you may have another situation on your hands. Quite possibly your pool has combined chlorine but not much free chlorine. If you do not know the difference between combined chlorine and free chlorine then please take a look at an earlier posting of ours called What is the Difference Between Total Residual Chlorine and Free Chlorine?

For those not interested in reading the long version, the following will explain free chlorine, combined chlorine and total chlorine:

• Free Chlorine does the active sanitizing of the pool water by neutralizing organic contaminants (i.e. bacteria, parasites, etc.). Traditional chlorine sanitized pools should have a healthy free chlorine level at all times.
• Combined Chlorine started out as free chlorine, locked horns w/ an organic contaminant, and now has become attached to the contaminant it neutralized. While still partially effective as a sanitizer, it has nowhere near the sanitizing power of free chlorine… and it plays a big part in producing the strong ‘chlorine smell’ most people associate with pool water.
• Total Chlorine represents the total concentration of free chlorine plus combined chlorine in a water sample.

So, Mandy, at this point we believe you should begin by making sure your test kit can test for both free and total chlorine. If it cannot then we suggest picking up a test kit such as the Poolmaster 5-Way Test Kit or, if you prefer a simpler chlorine testing method, the Pool Check 5-Way Test Strips should work quite well for you.

If your existing test kit can test for both free and total chlorine then you may need to replace your reagents (i.e. DPD-1 Test Tablets, DPD-3 Test Tablets, and/or DPD ReagentStrips). If stored near other pool chemicals, left out in the sun and extreme heat for long periods, or beyond their expiration date(s), your reagents may have gone bad.

Now that you have ruled out the test apparatus as the root of your chlorine troubles, test the pool for both free and total chlorine and then subtract the free chlorine concentration from the total chlorine concentration. Ideally you should get a very low number (zero would be perfect) but if you get more than a 0.5ppm difference you most certainly have a buildup of combined chlorine — and that would explain the strong chlorine odor you mentioned.

To get rid of the combined chlorine experts suggest ‘shocking’ (superchlorinating) the pool with a non-stabilized chlorine (contains no cyanuric acid) such as calcium hypochlorite powder or a non-chlorine ‘shock’ treatment such as monopersulfate (MPS).