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.

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.

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.

Today’s inquiry comes to us from a woman serving her country in the United States Navy. ‘Ronda’ had a question about the DPD products she had seen on our web site.

“Do your DPD Chlorine tabs work in Hach equipment?”

Good afternoon, Ronda, and thank you for this inquiry. When weighing the different DPD options (tablets, powders, reagentstrips, etc.) make sure you note the sample size that each test method will work in. As a general rule most devices that use DPD as a reagent will have 10 mL sample sizes, but we have also seen devices that use 15 mL sample sizes, 7 mL sample sizes and 20 mL sample sizes.

Check your machine’s manual to find out what sample size it takes. In order to remain compliant with whatever drinking water directives you follow you will need to match up the sample size w/ the correct reagent amount.

Specifically, though, you asked about the DPD tablets for chlorine testing that we have shown on our site and as far as we know all of the DPD products we have shown on our site work for 10 mL samples — except for the eXact Micro DPD products which work in smaller samples.

Two 10-mL Tablets/Strips/Powders for a 20-mL Sample?

While in theory that would work, definitely check your approved testing method to see if it expressly forbids that sort of thing and/or if it specifically calls for a brand or type of chlorine reagent delivery method. In the past we have seen where testing protocols have gotten so granular that they call out not only the type of DPD used, but also the brand of the test meter and DPD used for chlorine testing.

As we expected, the number of questions we received recently about swimming pool water has definitely increased. Today’s inquiry comes from a Water Testing Blog reader who hails from Pakistan and he/she asked:

Dear Sir/Madam,
hope you will be fine.i need some information regarding digital chlorine tester for swimming pool water .i read about extech cl200 testing metre.kindly send me the literature and price for it .
thanks
an early response is appreciable
farhan

Now before any of you go and criticize this person’s grammatical skills when typing in English, think more about the person’s commitment to keeping a proper chlorine level in swimming pool and the time it took to submit a question to this site.

WE commend ‘Farhan’ for his/her efforts and for transcending the language barrier to ask a question about proper chlorine testing in pool water.

On the topic of the “Extech 1200C” for chlorine testing in pool water, we took a look at the ExTech web site and did not find a meter in the chlorine/fluoride in water detection called the ‘Extech 1200C’… so we found ourselves a bit puzzled by your question.

We DID, however, see the ExTech CL200 Chlorine Testing Meter which uses Extech (CL203) Exstik ExTab™ Chlorine Reagent Tablets, a undoubtedly a proprietary blend of DPD-1 & DPD-3 reagents, to test for ONLY total chlorine concentrations in water.

The obvious problem we see with this meter for pool water testing, despite its USEPA credentials for total chlorine testing (in waste water), deal with the meter’s INability to test for free chlorine concentrations in water.

Proper Pool Water Testing Requires Free AND Total Chlorine Testing!

That heading said it all. Proper pool water care requires both free AND total chlorine testing.

Why? Quite simply, it does little good for the sanitation of a pool to have an in-range total chlorine reading with a very low, or non-existent, free chlorine reading. When that happens the pool contains mostly, if not entirely, chloramines (aka: combined/used chlorine molecules) which possess very little (limited) oxidizing power… and limited oxidizing power means limited sanitizing capabilities.

Improperly sanitized pool water can EASILY become a home in which various bacteria, parasites and viral ‘issues’ which will flourish, breed and infect swimmers if left unchecked.

Repeated Moral of the Story

Invest in a meter that test for both total chlorine concentrations AND free chlorine concentrations.

We suggest using a meter like the eXact Micro 7+ Pool & Spa Meter because it tests for not only free AND total chlorine, but also for Total Alkalinity, Bromine, Calcium Hardness, Copper, Ozone, Permanganate, and pH… all with the same meter!

Earlier we talked about the Extech’s USEPA credentials so naturally we figure you want to know if the eXact Micro 7+ Meter has credentials, too — and it does! When used with DPD chemistry (and the appropriate procedures, of course) the meter qualifies as an EPA Compliant device for testing free an total chlorine in drinking water.

“But Wait! There’s More!” Screamed the Announcer

As an added bonus, the eXact Micro 7+ Pool Meter also has the ability to test for Ammonia, Chloride/Salt, Chlorine Dioxide, Chromium Hexavalent, Cyanuric Acid, Iodine, Iron, Low Range Total Hardness, Manganese, Nitrate, Nitrite, Acid pH, Alkali pH, Potassium, Sulfate, Sulfide, and Turbidity — when operated in ‘% Transmission’ mode with the appropriate eXact Micro 7+ Reagent Strips.

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. We will begin by saying that you should immediately narrow your search by eliminating any water quality testing meters not using a form of DPD-1 as the reagent for free chlorine testing.

While ORP meters do offer a good bit of utility, their readings do not directly monitor just free chlorine content of water and a great number of water quality purists still feel that traditional DPD chemistry provides the best means of determining a sample’s relative safety — based solely upon the sample’s chlorine concentration, of course.

With that said, DPD comes in several forms: Liquids, Powders, Tablets, and ReagentStrips.

To answer John’s question directly, though, at this time Water Testing Blog recommends the eXact Micro 7+ Water Testing Meter as the ‘preferred’ choice for an inexpensive meter for testing chlorine concentrations — and 20+ other water quality parameters if users desire.

Yeah, yeah, we know… we almost ALWAYS suggest the eXact Micro 7+ Meter. This time, however, since John did ask specifically about an inexpensive chlorine testing meter, the fact that Filter Water Superstore (FilterWater.Com) has the basic meter kit on sale makes it even MORE of a good choice.

Pricing verified on 2/1/2012 and the basic test kit includes…

• 1 eXact® Micro 7+ Meter
• 1 bottle of eXact® Strip Micro DPD-1 (25 tests)
• 1 bottle of eXact® Strip Micro DPD-3 (25 tests)
• 1 bottle of eXact® Strip Micro pH (25 tests)
• 1 bottle of eXact® Strip Micro Total Alkalinity (25 tests)
• 1 bottle of eXact® Strip Micro Calcium Hardness (25 tests)
• 1 bottle of eXact® Strip Micro Copper (25 tests)
• 1 Mixing Cap
• 1 Cell Cleaning Brush
• 1 Instruction Booklet
• Plastic Carrying Case
• Four AAA Batteries to power the meter

What sort of detection range does the meter have? So glad you asked!

Naturally you will want to, or you should want to, know about the cost of replacement reagent(strips) for the meter. Since John asked about chlorine testing, below you will find links to, and pricing for, replacement DPD-1 and DPD-3 ReagentStrips — currently available at several online locations such as FiltersFast.Com and FilterWater.Com.

So if you find yourself in the market for a chlorine testing meter that uses an EPA Compliant testing method AND offers additional testing capabilities, definitely take a look at the line of eXact Micro 7+ Meters.

Recently we received a request for a quote on 5,000 DPD #1 Tablets for chlorine (or possibly another oxidizer) level testing. We’d like to remind remind everyone that although we link to a number of water quality products, Water Testing Blog does not stock or sell any products.

The party asking about DPD #1 Tablets sought to import them into a foreign country so we suggested they contact companies on the following page:

( http://www.alibaba.com/showroom/dpd-tablets.html )

… so they could attempt to save a few bucks (or whatever currency they use) on shipping.

Now having said that, when it comes to DPD #1 we believe anyone thinking about using DPD tablets should at least consider using DPD-1 ReagentStrips in their place. ReagentStrips dissolve faster and easier than tablets (especially in hard or cold water) and contain no filler materials that could interfere with photometric optics.

As far as performance, the manufacturer of DPD-1 ReagentStrips, Industrial Test Systems, Inc., had an independent laboratory conduct a blind water sampling study using DPD ReagentStrips, Tablets and Powder Pillows. In the end the ReagentStrips tested as good, and in some cases better, than other DPD reagent delivery methods.

OK, so maybe not ‘new’, but having spoken with the manufacturers of this product, we can safely say that a whole lot of people who could really use this product do not know of its existence.

For years people conducting tests for certain varieties of oxidizers (Free Chlorine, Chlorine Dioxide, Bromine, Iodine, and Permanganate) have relied upon DPD-1 tablets, DPD-1 powders and DPD-1 liquids to help them obtain accurate, repeatable results.

Now, however, an easier method of adding DPD-1 reagent to test samples has become available on FilterWater.Com, an online retailer of water quality testing and water quality improvement products.

Why consider switching to DPD-1 ReagentStrips?

• The United States Environmental Protection Agency has deemed the DPD-1 ReagentStrip test procedure equivalent to USEPA method 330.5 for wastewater when used in conjunction with a Palintest Chlorometer 1000 equivalent meter (i.e. the eXact Chlorine Photometer).

• The United States Environmental Protection Agency has deemed the DPD-1 ReagentStrip test procedure equivalent to USEPA method Standard Method 4500-Cl G for drinking water when used in conjunction with a Palintest Chlorometer 1000 equivalent meter (i.e. the eXact Chlorine Photometer).

• eXact DPD-1 Reagentstrips deliver a precise dose of DPD-1 reagent into a 10 mL sample without the need to count drops (DPD-1 liquids).

• Working in the field with DPD-1 Reagentstrips becomes much easier since testing personnel will not have to worry about small or large gusts of wind blowing away their reagent as they attempt to add it to a sample (DPD-1 powders).

• Due to the ‘dehydrated nature’ of DPD-1 Reagentstrips, they will dispense rapidly and easily into hard and cold water without the need for laborious, time consuming tablet crushing (DPD-1 tablets).

• As long a the test instrument (i.e. meter or test kit) uses as standard 10 mL sample size, an eXact DPD-1 Reagentstrip will provide consistent test results regardles of who made the test kit/meter.

If you use DPD-1 on a regular basis we think you owe it to yourself to give eXact DPD-1 ReagentStrips a try.

Note: For those who know a thing or two about DPD, you may find yourself wondering why we didn’t compare the DPD-1 ReagentStrip to an old school method of reagent delivery called ampuoles which involves breaking glass tips off into test samples. Ahem… Breaking of glass in order to perform testing. Need we say anything more about ampuoles?

Most people looking to test their drinking water for chlorine want to know the concentration of free chlorine, also called the free chlorine residual, in their drinking water. Basically speaking, free chlorine (hypochlorous acid) acts as an effective sanitizing and disinfecting agent in lower concentrations but can cause serious harm and damage to organic material (i.e. human skin, hair, cells, etc.) in higher concentrations.

The US Environmental Protection Agency has set the Maximum Contaminant Level (MCL) for free chlorine at 4.0 parts per million, also known as milligrams per liter (mg/L).

The most commonly used test for free chlorine residual uses a reagent called DPD (what is DPD?). More specifically, it requires DPD-1 and DPD-1 comes in several different forms: liquid, powder, tablet and reagentstrip form.