Today’s inquiry comes to us all the way from the United Kingdom. ‘Okello’ has interest in acquiring DPD test reagents for sanitizer/disinfectant level testing in water and asked, “I want the Quotation for DPD1-4″

At this time we carry 100 packs of DPD-1, DPD-3 and DPD-4 in the Water Testing Blog Test Kit Store.

Differences between DPD-1, 3 and 4?

For the answer to that question, we suggest that you take a look back at one of our earlier postings called What is DPD?. Not to brag, but we think that article does a decent job of answering the question.

To sum things up, though, below you will find the most common uses for DPD-1, DPD-3 and DPD-4:

• DPD-1 — Used by itself in a water sample to determine the free chlorine concentration in the sample.

• DPD-3 — Used after DPD-1 in a water sample to determine the sample’s total chlorine concentration.

• DPD-4 — Used by itself in a water sample to determine the total chlorine concentration in the sample.

So, before purchasing DPD, you may want to verify the type of chlorine testing that you will need to do — else run the risk of accidentally purchasing the incorrect DPD reagent(s)!

Where to purchase DPD?

As we stated earlier, you can purchase 100-packs of DPD-1, DPD-3 and DPD-4 from our Water Test Kit Store.

As for where to find other forms of DPD reagents, at this time we know of places to purchase two other forms of DPD: tablets and powder.

Need a new meter to test chlorine levels, too? We suggest looking at the eXact Chlorine Photometer available on the FilterWater.Com web site. It offers the reliability of DPD-based chlorine testing and the convenience of not having to match colors against a color chart.

Want accurate chlorine test results but don’t want to deal with DPD reagents and meters? Take a look at the SenSafe Free Chlorine water Check product currently available in our Water Test Kit Store. It bears USEPA Approval for use in municipal water testing and offers superior resistance to monochloramine interference that can sometimes affect the results obtained when testing for free chlorine residual using DPD test reagents.

After years of getting requests from loyal readers to open an online store where they could quickly and easily locate a lot of the products we frequently write about… we have finally taken the plunge and opened the Water Testing Blog Store.

Water Testing Blog Store Now Open

To start we have selected 20 water quality testing products that we feel do an excellent job of accurately measuring various water quality parameters that really and truly should matter to more people.

Examples: Arsenic, Bacteria, Chlorine, Metals, and, of course, everyone’s favorite in the Summer, Pool & Spa Water Quality.

Look for us to expand our offerings as time goes on and, as always, thanks for dropping by the Water Testing Blog… and don’t forget to test your water on a regular basis!

Recently we got asked who should consider installing a commercial water filter. The person who asked the question, Sylvan, owns for a restaurant whose tap water routinely tastes and smells like bleach water. Needless to say ice from their ice maker has a hideous taste and smell.

For the past few years Sylvan lugged 5 gallon bottles of water around and paid a ton of money each week just so that his customers didn’t have to eat food cooked in chlorine and drink water that he currently refers to as ‘pool water’.

Sylvan had his water tested by a local lab and also tested it himself (using SenSafe Free Chlorine & SenSafe Total Chlorine) and the results always showed that his water contained far less free and total chlorine than the MCL (Maximum Contaminant Level) set by the USEPA — but that certainly did nothing about the stench of chlorine in his water.

In a case like this where a whole KITCHEN in a restaurant needs better quality water we believe devices like inline filters for ice makers and undersink water filters will not get the job done.

For applications where multiple unwanted water contaminants need to get removed on a larger scale (i.e. for a restaurant’s kitchen), commercial water filters stand out as ideal filtration options.

Other places where commercial water filters make the most sense include large private residences (over 4000 sq.feet), businesses, manufacturing facilities, apartment buildings, retail establishments, and schools.

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.

When opening a swimming pool too many people forget to TEST THE WATER before adding chemicals… Whether you choose to test the water yourself w/ test kits like the eXact Micro 7+ Pool Testing Meter or Pool Check Test Strips, or visit your local pool supply store and have them test your water at the beginning of the season, you will want to test for all or as many of these water quality parameters as possible. Note:

• Alkalinity – Not having the correct amount of alkalinity in your water will make getting and keeping the pH of your pool water very difficult.

• Calcium Hardness – Having too much calcium in your water could result in deposits forming and could also make it harder for other chemicals to dissolve in the water. Too little calcium in the water could result in pool water becoming aggressive and starting to attack various pool surfaces.

• Chlorine (Free) – If you use chlorine as your sanitizer, check to see if you have any left over from last year… or risk adding more than you need to add at the beginning of the year and ‘wasting’ money.

• Chlorine (Total) – If you use chlorine as your sanitizer and shocked your pool at the end of the previous season (as you SHOULD have), then you may have a lot of combined chlorine in your water that needs to get ‘burned out’ w/ a non-chlorine shock. Combined chlorine does little good when it comes to keeping pool water clean.

• pH – Incorrect pH levels drastically reduce the effectiveness of important pool chemicals such as bromine, chlorine, clarifiers, algaecides, etc.

• Metals – Having unwanted metals such as copper and iron in your pool water when you shock it w/ an oxidizer like chlorine or bromine at the beginning of the season could cause the metals to precipitate out of solution and stain pool surfaces.

• Stabilizer – Also known as cyanuric acid, having too little of this compound in pool water makes it difficult to maintain a free chlorine residual. Having too much of it can keep chlorine in a pool from doing its job.

• Total Dissolved Solids – Too many total dissolved solids in pool water will result in the water not accepting additional material… such as the chlorine powder (granules), tablets, sticks, or pool chemistry balancing chemicals.

So, get your water tested before adding start-up chemicals. Any questions?

Most often when a person must perform chlorine testing on a water sample they have to use a chemical called DPD (What is DPD?) as the test reagent. DPD dissolved in water turns various colors (pale yellow through purple) in direct proportion to the concentration of oxidizers in the sample.

Today’s inquiry deals with DPD for free chlorine testing and came to us from ‘Oviruo’ who asked, “please can you assit me to get dpd satchet powdered type for testing free chlorine in water. thanks.”

We did a quick check and found that you can purchase DPD-1 Powder Pillows for Free Chlorine Testing on the Hach Company web site. The material has an approximate cost of around $21 per 100 powder pillows.

Alternative to powder pillows

A company called Industrial Test Systems came out with an alternative to the powder pillow that performs as well or better than the powder pillow. They called it the ReagentStrip and it works quite well without the mess that sometimes accompanies the act of trying to pour a small packet of DPD powder into a sample vial.

Below you will see how the DPD-1 ReagentStrip works when used with the Hach 890 Water Testing Meter:

Free Chlorine Testing Using DPD-1 ReagentStrip
and Hach’s 890 Water Testing Meter
click on image to view larger version

According to the manufacturer, DPD-1 ReagentStrips work with chlorine testing meters manufactured by well-respected companies such as Hach®, LaMotte®, Orion®, WTW®, and others.

Additionally, the DPD-1 free chlorine testing procedure stands and an equivalent to USEPA method 330.5 for wastewater and Standard Method 4500-Cl G for drinking water when used with a Palintest Chlorometer 1000 water testing meter or equivalent.

Cost of DPD-1 ReagentStrips compared to powder pillows

Earlier in this article we mentioned that interested parties can pick up 100 DPD-1 powder pillows for around $21 on Hach’s web site.

For those interested in the DPD-1 ReagentStrips, you can purchase 100 of those for around $19 on FilterWater.Com.

Today’s inquiry came to us from The United Arab Emirates and their inquiry dealt with DPD-1 (What is DPD?, the chemical reagent used to detect free chlorine in a water sample. Mohanad asked,

Dear Sir

Please could you quote a best price for: Chorine- DPD Free Reagent Qty:600 Pk, each pk containing 100 pillows

When testing for free chlorine most test methods use DPD-1 as the test reagent, though in the United States the USEPA has approved an alternate method (SenSafe Free Chlorine Water Check) for testing free chlorine levels in drinking water.

Where to Buy DPD-1 Test Reagents

We have found that online pool stores such as serve as very convenient place to purchase DPD-1 test reagents. As of right now, In the Swim has 1,000 DPD-1 tablets (for use in 10mL samples) available for less than 5 cents per test!

Easier to Use Form of DPD-1 Chlorine Test Reagent?

Looking for an equivalent but easier way to test free chlorine using your existing meter or test system that uses a 10mL sample size? If so, DPD-1 ReagentStrips function the same as or better than traditional DPD-1 test tablets, powders and liquids.

For a simple demonstration of how the DPD-1 ReagentStrips for free chlorine testing work in a Hach water quality testing meter, take a look at this free chlorine testing flowchart that illustrates how much easier DPD-1 ReagenetStrips make free chlorine testing.

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!

Every once in a while we get a question about a topic related to water quality, but not quite a water quality question… so today’s question came to us from ‘Michael’ who asked,

I need to purchase a quick test means to locate water leaks in supply pipes to my residential water service meter. The county water uses a small tear able foil packet of chemicals that turns red when mixed with chlorinated water. My home has very low water pressure and volume, we are serviced by an extremely old and much damaged 2″ pvc line serviced by the Logan County PSD, Logan WV. The PSD does not have the time or personnel to investigate all of the water puddles located in the community where I live. I would like to be able to quickly and safely test any ground water in the hope of finding where the line rupture is.

Thank you, Michael, for this inquiry. From the sounds of things your local water department uses DPD powder pillows or tablets to investigate the nature of puddles suspected to have formed as a result of leaks in municipal water lines. The chemical DPD turns various shades of pink through dark red in the presence of oxidizers such as chlorine, bromine, ozone, etc.

Where can the average citizen get DPD?

Chemical supply houses often carry DPD powder and/or tablets in bulk and many swimming pool stores tend to carry DPD powder pillows and tablets intended to work with swimming pool test kits.

For what you want to do, though, we suggest you look more closely at DPD powder. Specifically we think you should focus your acquisition efforts on DPD-4, a compound which will detect both free chlorine and combined chlorine in a water sample. This matters because once water treated with free chlorine exits a controlled environment (i.e. leaves the pipe through a crack, fissure, etc.) the free chlorine will immediately begin acting on any and everything in its environment… and that will result in only combined chlorine possibly reaching the surface and creating a pool of water.

Problems with testing puddles for chlorine?

While not totally impossible that a pool of chlorinated water could potentially wind up on the surface over or near a leak from a chlorinated municipal water line, we believe that only a good sized leak could produce water in the volume required to get water containing highly reactive chlorine molecules through contaminant filled soil and up to the surface — with readable/detectable chlorine residual levels high enough to detect visually (or with a portable meter) using DPD.

But, since your local water department does it, either your water line infrastructure routinely has large leaks or its water lines lie very close to the surface. Either way, a swimming pool supply company called In the Swim carries DPD-1 tablets and DPD-3 tablets.

Crushing (carefully) and then mixing them (carefully) in equal parts should enable you to create your own version of DPD-4, but to play it safe we suggest using the appropriate amount of DPD-1 in a 10 mL sample of water and then using the DPD-3 in that same sample — per the ‘accepted’ procedures for free and total chlorine concentration determination.

Web sites have flaunted the results of studies about bacteria on and around the ice machines and soda fountains in the food service industry (especially the self-service ones. Yuck!) but today’s email inquiry comes to us from ‘Jacky’ who said,

“My friends and I own a small eatery with a bed-n-breakfast in the mountains and we have water from the town. Every once in a while the news tells us to boil until further notice. The last time it happpened a customer asked how long they could have been drinking bacteria water before the news told us to boil the water. I said we don’t know and they said we should know that sort of thing before we serve people food and drink. How long COULD the water have been bad?”

From the sounds of things you had a real snot eating or staying in your place. We hope he/she at least tipped well and didn’t cause you any other grief!

Regarding the answer to the question asked, you will have to talk to the town water department and ask them for information on their bacteria testing policies and public notification policies since some municipal water systems have tighter, more stringent testing requirements than others — but none can get any looser than those set by the State & Federal Governments.

Regular testing for bacteria?

We assure you that your local water department, if it follows State and Federal Water Treatment & Testing Guidelines, performs regular testing for bacteria, testing for chlorine and tests for a host of other important water quality contaminants and water quality parameters on a regular basis.

If you want more detailed information on the steps used by your local water company to protect you from bacteria and other unwanted drinking water contaminants, we suggest that you contact your local water department directly.

As we mentioned, city and municipal water departments take specific, regulated steps to protect their customers from bacterial contamination… but even in the best of circumstances sometimes things happen which could possibly put those customers at risk.

Water main breaks between the water treatment plant and customers’ homes as well as unexpected equipment failures at the water treatment plant can both certainly happen at any time and both may result in opportunities for bacteria to enter the drinking water supply.

Personal protection against bacterial contamination?

Recently a number of folks have started installing UV water sterilizers like the Crystal Quest UV 6 in their homes as a final layer of protection against bacterial contamination. These devices render bacteria unable to reproduce by exposing the unwanted critters to a specific wavelength of UV light.

So, while the devices do not necessarily kill the bacteria right away, UV water sterilizers like the Crystal Quest UV 6, when used in the right application, make certain the organisms do not have a chance to multiply and create problems for those who ingest them.

Please note, however, that UV water sterilizers should NOT get used as the first line of defense against bacteria when dealing with untreated and/or unfiltered water.

Why? Because UV water sterilizers can do nothing to remove unwanted particles, solids and/or chemical contaminants. To remove things of that nature one should consider a unit that uses activated carbon, reverse osmosis, ultrafiltration, etc.

WaterFilters.Net carries a large selection of water filter systems and replacement water filters for use in private residences as well as a wide range of commercial applications.

While on the topic of commercial water filters…

Jacky had concerns about water quality in a commercial setting so it only makes sense that we end this article by mentioning the CQE-UV-00105, a commercial UV water sterilizer with a flow rate greater than 22 GPM.

Crystal Quest CQE-UV-00105