DPD testing tablets

DPD Testing Tablets

Regular price £54.75 £0.00 Unit price per

What are DPD testing tablets?

DPD testing tablets are used to measure the level of halogen in the water between 0.001m/l to 10mg/l. While there are four different types of DPD tablets in total, only DPD1 and DPD3 are available to purchase through SOCOTEC’s online Shop.

Why do you need DPD testing tablets and where can they be used?

Chlorine and bromine serve as a primary disinfectant due to its effectiveness in killing potentially harmful organisms, and having the right measurement of halogen within the water is essential in order to prevent irritation and contamination associated with overexposure. DPD testing tablets are used to accurately determine halogen levels in cooling towers, water features, swimming pools, spas and hot tubs, as well as for measuring levels within water used for drinking and other industrial processes.

How do DPD testing tablets work?

DPD1 tablets measures the level of free halogen, which kills any remaining bacteria, while DPD3 measures combined halogen. Both DPD1 and DPD3 samples must be added together in order to work out the total halogen level within the water. If the tablet has turned a grey/brown colour, this means that it has deteriorated and is therefore no longer fit for use as it will provide false and inaccurate results.

To use the DPD test accurately, please adhere to the following instructions:

  1. Ensure that all equipment is clean prior to use
  2. Fit the correct disc to the comparator before rinsing two 10ml calibrated test tubes in sample water three times
  3. Fill the first test tube with 10ml of water, followed by a smaller quantity of water in the second tube
  4. Place a DPD1 tablet into the second test tube and shake slightly to dissolve
  5. Fill up the second test tube up with water until the quantity of liquid reaches the 10ml mark
  6. Place the test tube into the right hand side of the comparator and rotate the disc to achieve a colour match
  7. Take the reading as quickly as possible to obtain an accurate Free halogen Residual reading
  8. Place a DPD3 tablet into the same test tube, dissolve the tablet and allow a minimum of two minutes for the full colour to develop
  9. Insert the tube back into the comparator and rotate the disc to obtain a colour match
  10. Note the reading as quickly as possible to achieve an accurate Total Halogen Residual
  11. Subtract the reading obtained from the Free Halogen Reading from that obtained in the Total Halogen Residual Reading to achieve the Combined Halogen Value for the sample.

What are the benefits of using DPD testing tablets?

It is essential to work out the right amount of halogen that needs to be added to a body of water – too much can increase the risk of toxicity and inhalation, while too little can result in bacterial growth and risk the growth of bacteria such as Legionella. DPD tablets are an efficient and accurate way of ensuring that the chlorine levels are kept within the ideal limits required to ensure health and safety of all those who may come into contact with the water.

    Please note that the DPD testing tablets can be used with comparators only and will not be compatible with photometers.


    DPD testing tablets are available for purchase via credit/debit card, as well as on Apple and Google Pay. Please contact us if you would like to pay via bank transfer or raise a PO.

    Contact us

    If you are interested in finding out more about DPD testing tablets or how SOCOTEC can support you with its wide range of Water Treatment & Hygiene services, click here or get in touch.