DPD dispenser for chlorine testing


Use in field tests for free or total chlorine in water for 5 mL and 10 mL samples.

  • Dispense reagent with the press of a button.
  • Avoid messy powder handling and leftover foil pouches.
  • Refill dispenser quickly and easily.

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  • Eliminates foil packets.
  • Recessed mouth fits different sized sample vials.
  • Works with wide range of colour cubes, colour wheels, and colorimeters.
  • Colour coding distinguishes free and total chlorine tests.

  • Dispenses reagent in one quick step.
  • Reduces hands-on time.
  • Refill vials screw on quickly and easily.


How EZ DPD works

EZ DPD dispenses a premeasured dose of N, N-Diethyl-p-phenylenediamine (DPD) into a 5 mL or 10 mL sample. The DPD reacts with chlorine in the sample to produce a pink colour change. The intensity of the colour is proportional to the amount of chlorine in the sample.


Colorimetric test kits (not currently sold by IDEXX) allow the sampler to interpret the intensity of the colour change, providing a quantitative measure of the amount of chlorine in the sample. EZ DPD detects chlorine between 0.1–3.5 parts per million (ppm).

How to use




  • Fill sample vial (not from IDEXX) with water you wish to test.
  • Place EZ DPD over sample vial and press button once.
  • Read results according to procedure explained in your test kit.


  • To refill, unscrew empty reagent vial.
  • Uncap refill vial and screw into dispenser top.


  • EZ DPD works with a wide range of chlorine test kits.

Frequently asked questions


The Surface Water Treatment Rule of 1989 requires that distribution systems using surface water as a source and serving more than 25 people disinfect the distribution system or meet maximum HPC levels. Disinfectant residual level must be ≥ 0.2 mg/L (ppm), or the HPC level must be below 500 cfu/mL. The disinfectant residual must be present in ≥ 95% of samples for 2 consecutive months.

Testing frequency requirements:

< 500 1
501—1000 2
1001—2500 3
2501—3300 4
> 3300 continuous

Chlorine present as Cl2, HOCl, and OCl— is free available chlorine. The active chlorine in the water for disinfection is also called free chlorine residual.

Combined chlorine is that which is bound to other elements or organic compounds but is still an effective disinfectant. Combined chlorine has been found to be more effective than free chlorine in controlling postdisinfection bacterial growth. Chloramines are an example of combined chlorine.

Chloramines are compounds formed by the reaction of chlorine and ammonia nitrogen in water.

Total chlorine is the combination of free chlorine and combined chlorine.

Residual chlorine is the chlorine that has not combined with organic matter.

The EZ DPD Test dispenser will deliver 0.04–0.09 grams of DPD powder each time the button is pressed.

The EZ DPD Test detection range is from 0.1–3.5 ppm.

Standard Methods for the Examination of Water and Wastewater, Section 4500-CI, G describes the DPD colorimetric method for field testing chlorine.

Yes. Press the button 3 times for each 25 mL sample.

Remove the dispenser from the vial and clean it to dislodge any plugs. This can be done with a swab or other small device. The dispenser can also be cleaned with water. If you clean the dispenser with water, make sure it is dry before putting it back on a vial of reagent.

If the powder clumps, shake the vial to ensure free-flowing powder before dispensing.

EZ DPD is capable of working with many products on the market, including: Hach Pocket Colorimeter, Hach colour wheel, Hach colour cube, and LaMotte colorimeter.

Hach and Pocket Colorimeter are trademarks of the Hach Company. LaMotte is a trademark of LaMotte Chemical Products Company.

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