Order Code Product Unit
Reagent tablets for GPT-Photometer

DPD No.1


Refill pack with 250 tablets

1 Piece


Refill pack with 500 tablets

1 Piece

DPD No.3 for combined and total chlorine (in combination with DPD No.1)


Refill pack with 250 tablets

1 Piece


Refill pack with 500 tablets

1 Piece

Cyanuric acid


Refill pack with 250 tablets 1 Piece



Refill pack with 250 tablets

1 Piece


Refill pack with 500 tablets

1 Piece

Order Code Product Unit
Liquid reagent for GPT-Photometers and Photometers from other manufacturers for the determination of Chlorine-, Ozone- and pH value  

Reagent solution A1
for approx. 150 measurements

16 ml


Reagent solution A2
for approx. 150 measurements

12 ml


Reagent solution B
for approx. 150 measurements

16 ml


Reagent solution pH Phenolred
for approx. 50 measurements

16 ml

Design of labels depending on quantity – possible according to your template please contact us!

Notes on chlorine, ozone and pH value determination

Chlorine reagent A1 for approx. 150 measurements, content 16 ml
Chlorine reagent A2 for approx. 150 measurements, content 12 ml
Chlorine reagent B for approx. 150 measurements, content 16 ml
pH reagent indicator solution for approx. 50 measurements, content 16 ml

Implementation of the determination of:

1. Chlorine (free)

  • first 3 drops A1 (buffer)
    then 2 drops A2 (DPD reagent solution)

    drop into the empty cell. Fill the cell up to the 10 ml mark with water, stir or swivel slightly and measure after approx. 1 minute.

    result = mg/l free Chlorine

2. Chlorine (total)

  • Add reagent solution B for total Chlorine measurement as follows:
    in water sample above 3 drops of solution B
    add, swivel slightly and read value after approx. 1 minute

    result = mg/l total Chlorine

3. Chlorine (combined)

  • result of the determination 2.
    result of  the determination 1.
    = mg/l combined Chlorine

4. pH value

  • pH indicator solution for pH range 6,5 – 8,4
    6 drops in 10 ml water
    swivel slightly and read off the pH value.

5. Ozone (in absence of chlorine)

  • The measurement is carried out with the GPT photometer in chlorine mode.
    First 3 drops of solution B into the empty cell, fill up to the 10 ml mark with test water
    then 3 drops of DPD solution A1
    then 2 drops of solution A2 add and swivel, read value after approx. 2 minutes

    read value
    x factor 0,677
    = mg/l Ozone

Green Chemistry
In order to control water quality, reagent tablets are common. This indicator-system is the most easy and reliable system in our opinion.With all our reagents, we keep the formulation as environmentally friendly as possible. Hazardous substances are – whenever possible – replaced by harmless and functionally identical substitutes.For example, our reagents for Pool & Spa water testing are free from boric acid, which is still frequently being used as an additive in the industry. The European Union (EU) has classified boric acid as a dangerous substance.The DPD No.1 tablets are not only 100% free from boric acid, they also guarantee compliance with the buffering effect required by the standard ISO 7393/2:2012-17. This characteristic makes the tablet a leader in its field.

Essentially there are two types of tablets:

  1. Reagent tablets with green print on the blister packages dissolve rapidly when they get in contact with water. These so called rapid-tablets are used in Mini-Testers.
  2. Reagent tablets with black print on the blister-strips develop a clear, coloured solution after they have dissolved in water samples by using a stirring rod. This high quality standard allows to guarantee a durability of five to ten years, provided the blister-packaging is undamaged! Each tablet is individually sealed and fresh until removal. A precise dosage of reagent and an easy handling provide high accuracy of analysis. Due to alu-blister-packaging, which is also used in pharmaceutical industry, a comfortable withdrawal by pressing is guaranteed. The DPD-reagent-tablets correspond on national and international basis to DIN EN ISO 7393-2 for examination of water quality concerning free chlorine and total chlorine.

Green and chemistry: can that work?

It’s definitely not a contradiction. Green chemistry is an issue that experts in the field have been discussing for well over a decade. It refers to the industry’s efforts to produce its products in a way that is as environmentally friendly as possible and conserves resources wherever possible. To be specific, for us, it’s about avoiding hazardous substances and sustainability. As a German company with a close relationship to our customers, Green Chemistry is an idea that we are especially committed to.

For example, since 2010 we have, wherever possible, systematically avoided using boric acid in our DPD tablets and other tablet products.

Why avoiding boric acid?

It goes back to EU substance testing and regulation. Boric acid was classified as a so-called ‘substance of very high concern’ by the European Chemicals Agency, ECHA. This means that the substance is not only generally labelled as hazardous, but at the same time, the classification also means that industry should avoid using it.

Why is using boric acid a problem?

Among other things, boric acid can have adverse effects on the ability to reproduce!

If we look around the market, then we will find many competitors’ products that still contain boric acid. Consumers are still uninformed about this issue and are exposing themselves to a risk. This is why we want to create transparency with the Green Chemistry logo and educate consumers.

Why should customers use a product containing hazardous substances when hazard-free alternatives are available at no extra costs?

Is avoiding boric acid the only step you are taking with your Green Chemistry initiative?

We’re constantly improving the formulations of our reagents and test kits in response to new solutions. A large number of our reagents were improved for this reason. And we will continue to systematically move forwards in this direction.

Does the composition of reagents influence the quality of the measurement results?

Very rigorous quality criteria apply to GoPoolTest products. That means that for every new test developed and every reagent offered for sale all the requirements of the current measurement must be fulfilled – without any exceptions. The fact that we research, develop and manufacture in Germany really pays dividends here. It gives us access to decades of experience and excellent specialists. We don’t put any new test on the market without extensive approval and verification processes.

Our customers can therefore be sure that all Green Chemistry reagents offer the same excellent measurement performance. They don’t have to accept any reduction in measurement quality.

Do all the companies on the market take the same approach? 

Some of our competitors’ DPD tablets still contain boric acid. But we can only speculate as to why that is. The fact is that the change process takes a lot of expertise, time and money. After all, you don’t want to lose the special benefits of reagent tablets: their exceptionally long shelf life of 5-10 years and precise dosing accuracy. What’s more, DPD tablets must not shed the ability to buffer different pH values in the test. ISO 7393-2 is critical here, too. It makes the unique quality and performance of GoPoolTest DPD tablets especially clear.

Is the indicator Ortho-Tolidine (OTO) an alternative method?

There ist no reason why some distributors and customers continue to sell or use orthotolidine (OTO) to detect chlorine – and for domestic use, of all places. It is well known that OTO is carcinogenic, so it is classified as toxic, poisonous. What’s more, OTO only determines total chlorine and not the active free chlorine, as is required. And price is no longer an issue today. So why should our customers be exposed to a health hazard for no reason and completely unnecessarily, especially when there’s a real alternative with DPD Green Chemistry? This is also one of the principles of the law of substitution, which states that where a safer and better alternative exists, then the more hazardous product should be discontinued. So there is no valid reason to continue to use OTO.

How exactly do we plan to ensure that this issue becomes front of mind for customers?

The first step in communicating this message is our Green Chemistry logo. Users and consumers can then see at a glance which of our products already fulfil the requirements of this concept. We also hope that our customers who use our reagents in their own products will respond positively to the logo, and ideally, we hope that they will adopt it. We’ll be delighted if, in this way, these products were able to communicate the benefits of green chemistry to end consumers, too.