These genuine Water-ID DPD No. 3 photometer-grade tablets are the essential reagent for measuring total chlorine (and combined chlorine by calculation) as well as ozone in swimming pool and spa water. Used directly after a DPD No. 1 free-chlorine reading, they complete the full chlorine picture that every pool owner or technician needs to keep water safe and properly dosed. Each pack contains 50 tablets, individually sealed in aluminium push-through blisters to protect against moisture and contamination.<\/p>\n
Free chlorine does the active sanitising work, but combined chlorine \u2014 formed when chlorine reacts with bather waste and organic matter \u2014 is far less effective as a disinfectant and is responsible for the characteristic pool odour and eye irritation associated with chloramines. By adding a DPD No. 3 tablet to the cuvette immediately after the free-chlorine DPD No. 1 reading (without emptying it), the photometer captures total chlorine; combined chlorine is then calculated as the difference between total and free. Keeping combined chlorine low \u2014 typically below 0.2 mg\/l \u2014 signals a well-maintained, safe pool.<\/p>\n
These tablets are formulated exclusively for use with Water-ID PoolLab 1.0 and PoolLab 2.0 photometers. Always use the photometer-grade version (black print on the blister reverse) \u2014 not the Rapid tablet variant \u2014 to ensure the device delivers accurate, reliable readings. For ozone testing on compatible PoolLab devices, DPD No. 3 is also required alongside DPD No. 1; if chlorine is also present in the sample, Glycine tablets are additionally needed.<\/p>\n
For best accuracy, crush the tablet in the cuvette with a clean stirring rod, allow the full two-minute reaction time before reading, and always use the light-protection cover during measurement. Store tablets in a cool, dry place between 15\u201325 \u00b0C; the aluminium blister packaging actively guards against humidity to maintain the two-year shelf life. Thoroughly rinse the cuvette, cap, and stirring rod after each DPD No. 3 test to prevent cross-contamination of subsequent measurements.<\/p>","protected":false},"excerpt":{"rendered":"