Test Conclusion
UKAS Accredited Laboratory
ChloroKlean Plus at concentrations of 83ppm, 60ppm and 50ppm met the log reduction requirements as specified in EN 13623 (4 lg) with a contact time of 60 minutes for Legionella pneumophila NCTC 11192.
Test Conditions
Test Standard
BS EN 13623:2020
Test Temperature
30°C
Contact Time
60 minutes
Test Organism
Legionella pneumophila NCTC 11192
Additional Test Parameters
- Interfering Substance: Yeast Extract (0.0005% final concentration)
- Diluent: Buffered ferrous hard water
- Neutralisation Method: Membrane Filtration using Rinsing Diluent with Sodium Thiosulphate
- Incubation Temperature: 36°C
Results by Concentration
The standard requires a minimum 4 lg (log) reduction in bacterial count to pass. Results at different ChloroKlean Plus concentrations:
About BS EN 13623:2020
BS EN 13623:2020 is the European standard for evaluating the bactericidal activity of chemical disinfectants against Legionella in aqueous systems. It is a Phase 2, Step 1 quantitative suspension test that establishes the baseline efficacy of products under controlled laboratory conditions.
Test Purpose
Evaluates whether a disinfectant can achieve the required 4 log reduction against Legionella pneumophila under standardised conditions relevant to cooling water systems.
Regulatory Relevance
EN 13623 testing supports BPR product authorisation claims and provides evidence of efficacy for HSE compliance under HSG274 and ACOP L8 guidance.
Practical Implications
These laboratory results translate directly into real-world water treatment performance. The ability to achieve greater than 4-log Legionella reduction at low concentrations means that ChloroKlean Plus can maintain effective disinfection in cooling water systems while minimising chemical usage and operating costs.
ACOP L8 Compliance
The proven 4-log reduction supports compliance with HSE Approved Code of Practice L8 for Legionella control in evaporative cooling systems, hot and cold water systems, and other risk environments.
HSG274 Part 1
EN 13623 test data provides the evidence base required under HSG274 Part 1 guidance for selecting effective biocide treatments in cooling tower water management programmes.
Ongoing Monitoring
In practice, continuous low-level chlorine dioxide dosing (typically below 0.5 ppm) provides sustained protection. Regular monitoring with DPD test kits confirms residual levels are maintained throughout the system.