Water Quality: Testing, Filters for, and Purification of Drinking, Ground and Pool Water » DPD

Liquid Reagent Turns Yellow in Presence of Chlorine

Water Testing Blog — Tue, 31 Jan 2012 13:03:15 +0000

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).

Pool Test Kit for Total Chlorine & pH
Using OTO and Phenol Red

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!

Turns Red When Mixed With Chlorinated Water — Leak Detection

Water Testing Blog — Tue, 17 Jan 2012 18:16:56 +0000

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.

DPD Test Tablets
DPD-1 & DPD-3 for Chlorine Testing

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.

Do the DPD Tablets Work in Hach Meters?

Water Testing Blog — Thu, 10 Nov 2011 13:03:00 +0000

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.

(100) DPD #1 Tablets
(1,000) DPD #1 Tablets

(100) DPD #3 Tablets
(1,000) DPD #3 Tablets

Chlorine Testing Meter for Swimming Pool?

Water Testing Blog — Fri, 01 Jul 2011 13:03:03 +0000

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.

ExTech CL200 Total Chlorine
Testing Meter for Water

ExTech CL203 Total Chlorine
Test Reagent Tablets

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.

eXact Micro 7+ Pool Testing Meter

eXact Micro 7+ ReagentStrips

Electronic Pool Testing Meter

Water Testing Blog — Fri, 20 May 2011 14:06:17 +0000

As usual the warmer weather (in most of the US) has brought out the folks who have questions about pool water and how best to take care of it. Today’s question comes from ‘ActionLassie007′ who asked,

eXact Micro 7+
Pool Testing Meter

“Do they make meters for pool testing that regular people can afford? Last yr our poolguy had a meter and I asked him how much it cost. He told me one thousand and some change. He lie to me so I would not go get one and he loses a customer?”

Wow. Interesting situation, right? Personally we’d have fired the guy for telling an outlandish lie. Yeah, sure, SOME equipment used to test pool water MAY cost upwards of a thousand dollars or more, but would the average pool maintenance person REALLY spend that kind of money? We doubt it.

We suggest, Lassie, that you take a look at the eXact Micro 7+ Pool Water Testing Meter… which costs well under a thousand dollars, by the way.

Pool & Spa News
Readers’ Choice Award Winner

Combining the reliability and repeatability of a photometer w/ the dependability of proven chemistry methods such as DPD (for chlorine testing) and phenol red (for pH testing), the eXact Micro 7+ Pool Testing Meter puts the power of accurate water testing into the hands of the people who need it most: pool owners.

A definite advantage offered by this particular pool meter: Versatility. The pool testing meter tests for 7 critical pool water parameters directly and with the use of a conversion chart and correct reagentstrip it can test for a number of other water parameters, as well.

What comes in pool water test kit?

In the basic kit you will find everything you need to test for free chlorine, total chlorine, pH, calcium hardness, total alkalinity, dissolved copper, and cyanuric acid.

Question: When Disinfecting My Well, How Do I Know That I’ve Put Enough Chlorine Bleach In?

Water Testing Blog — Fri, 29 Apr 2011 03:20:16 +0000

We may have addressed this matter in the past, but we would rather repeat ourselves a dozen times on a topic like this than have people not properly disinfecting their wells.

Today’s inquiry comes from ‘DdavidD’ who asked, “Hi hope you can hlep. We got a well bleach kit from the hardware store to clean our well and want o know how we know when enough has been added. Directions tell us to test but what do we test with? Thanks”

Most kits for disinfecting a well contain instructions for properly using their contents and we HIGHLY suggest that you follow the darn things — else risk using too little and not getting the job done or adding too much and risk damaging your well equipment.

Most kits will recommend maintaining levels of free chlorine much higher than any DPD Reagent Based Water Test Kit can possibly detect without messy dilutions which, if not done carefully, can easily result in flawed free chlorine readings.

So… how can a person test for 20, 50 or even 100+ ppm free chlorine? Simple: SenSafe/WaterWorks manufactures a product called High Range Free Chlorine which can detect up to 120 ppm free chlorine in just a few minutes without the user needing to mix chemicals or perform dilutions.

If you need to test for even HIGHER levels of free chlorine than 120 ppm, then we suggest you take a look at the Ultra High Range II Free Chlorine Test Strips contained in the Childcare Sanitizer/Disinfectant Water Test Kit.

Don’t let the word ‘childcare’ in the name fool you. The makers of this ultra high range free chlorine test strip designed it specifically for use in average tap/well water that contains super high levels of free chlorine — up to 2,000 parts per million free chlorine!

Detect Up to 2,000 ppm Free Chlorine w/ a Test Strip!

Inexpensive Meter for Free Chlorine Testing

Water Testing Blog — Mon, 07 Feb 2011 00:05:15 +0000

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.

EPA Compliant Meter for
Free & Total 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.

Filters Fast Web Site

* Free Chlorine ReagentStrips 486637 — DPD-1. Used to test for free chlorine residuals. Around $13.

* Total Chlorine Test Strips 486670 — DPD-4. Used to test for total chlorine, but does NOT require the use of DPD-1 first, unlike the DPD-3 reagentstrips that come with the basic kit. Around $14 for 100 tests.

Filter Water Web Site

* ITS-EZ7-486637 — DPD-1 used for free chlorine testing. Around $13 for 100 tests.

* ITS-EZ7-486638 — DPD-3 used for free chlorine testing. Requires use of DPD-1 first. Around $8 for 100 tests.

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.

Wanted: 5,000 DPD #1 Tablets for Chlorine Testing

Water Testing Blog — Tue, 18 Jan 2011 13:03:26 +0000

1,000 DPD #1 Tablets

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.

DPD #1 ReagentStrips

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.

Locating a Hanna Checker HC Photometer for Free Chlorine

Water Testing Blog — Mon, 27 Dec 2010 13:03:21 +0000

Hanna Checker HC
Chlorine Photometer

Every once in a while we get requests from foreign countries asking for pricing and availability of specific products.

Unfortunately we do not know a whole lot about the International market and what products exist in countries outside of the United States and Canada, but we generally assume that interested parties can acquire the same stuff we can, just at a higher cost due to import taxes and shipping fees.

Having said that, though, today’s international inquiry comes from ‘Zahid Afzal’ in Pakistan who asked who wants to know, specifically, about places to purchase a product called the Hanna Checker HC Photometer for Free Chlorine

Dear Sir/Madam,

Can you please give us the price for the “Hanna Checker HC Photometer for Free Chlorine” for our project in the Flood affected areas of Pakistan.

Regards,

Zahid Afzal

Thanks for the inquiry, Zahid. We really don’t know all that much about the “Hanna Checker HC Photometer for Free Chlorine“… except that a swimming pool supply company ( In the Swim ) began carrying this product at some point last Summer.

Having said that, do you really want to use a pool water testing device to test drinking water?

Granted we have said over and over again that doing ANY testing of drinking water in an area recently affected by flood waters makes more sense than performing no testing at all, but we would suggest looking into other meters… or possibly even into simpler testing methods that do not rely upon chemical reagents (i.e. DPD powders, DPD tablets, DPD reagentstrips, DPD liquids, etc.)

WaterWorks 2 Free & Total Chlorine Test Strips

EPA Approved SenSafe Free Chlorine Test Strips