HSE Guidance on Water Treatment: Where ChloroKlean Fits

Understanding the HSE framework for water treatment in the UK

The Health and Safety Executive (HSE) publishes a family of guidance documents that together set the standard for managing waterborne risks in the UK. For anyone responsible for water systems - from hospital estates managers to leisure centre operators and hydrotherapy centres - these documents define what compliance looks like.

ChloroKlean is a blend of sodium hypochlorite and sodium chlorite that activates in situ to generate chlorine dioxide. This formulation means it delivers both an HSE-approved primary disinfectant (sodium hypochlorite) and the additional biofilm-penetrating capability of chlorine dioxide - all from a single product. Understanding where ChloroKlean sits within the HSE guidance framework is important for anyone considering the switch.

"The HSE framework is built around practical, proven chemistry. ChloroKlean works within that framework because its sodium hypochlorite base is the same approved chemistry that the guidance recommends, while the in-situ chlorine dioxide generation adds a level of biofilm and pathogen control that sodium hypochlorite alone cannot achieve." - Gavin Owen, Managing Director, ChloroKlean

ACOP L8: the legal foundation

The Approved Code of Practice L8 - Legionnaires' disease: The control of Legionella bacteria in water systems - sits at the top of the HSE guidance hierarchy. Unlike standard guidance documents, ACOP L8 has special legal status. If you are prosecuted for a breach of health and safety law and it is proved you did not follow the relevant provisions of the Code, you will need to show the court that you complied in some other equally effective way.

ACOP L8 requires duty holders to:

• Identify and assess sources of risk from Legionella in water systems
• Prepare a written scheme for preventing or controlling the risk
• Implement, manage, and monitor precautions
• Keep records and appoint a responsible person

ACOP L8 does not prescribe specific chemicals. It requires that duty holders use effective water treatment as part of their control scheme. The supporting technical guidance - HSG274 - provides the detail on how to achieve this.

ChloroKlean's relevance to ACOP L8 is straightforward: it provides effective, documented water treatment using approved chemistry. The sodium hypochlorite component is the most widely used chemical treatment for Legionella control under this framework, and the in-situ chlorine dioxide generation provides additional efficacy against biofilm - the primary harbour for Legionella bacteria in water systems.

HSG274: the technical detail for Legionella control

HSG274 is the companion technical guidance to ACOP L8. While ACOP L8 tells you what you must do, HSG274 tells you how to do it. It is published in three parts:

HSG274 Part 1: cooling towers

Part 1 covers evaporative cooling systems including cooling towers, evaporative condensers, and similar plant. These are high-risk systems for Legionella because they generate aerosols from warm water - ideal conditions for Legionella transmission.

Chemical treatment is a core requirement. The guidance requires effective biocide programmes to control microbiological growth, with regular monitoring of biocide levels and microbiological counts. Sodium hypochlorite is one of the most commonly used oxidising biocides in cooling tower treatment.

ChloroKlean's sodium hypochlorite base aligns directly with this requirement. The chlorine dioxide generated in situ provides the additional benefit of penetrating and removing biofilm from cooling tower fill, drift eliminators, and distribution systems - areas where Legionella colonies become established within the protective biofilm matrix that sodium hypochlorite alone struggles to reach.

HSG274 Part 2: hot and cold water systems

Part 2 is the most widely applicable section, covering the hot and cold water systems found in virtually every commercial building - hospitals, care homes, hotels, schools, offices, and leisure facilities.

This section explicitly references chlorine dioxide as an accepted chemical treatment method for Legionella control in building water systems. The guidance covers ongoing chemical dosing, system disinfection, and monitoring requirements.

Key points relevant to ChloroKlean:

• Chlorine dioxide is a recognised treatment option for ongoing Legionella control in hot and cold water distribution systems
• The guidance acknowledges that biofilm in pipework is a significant reservoir for Legionella bacteria
• Chemical treatment must maintain an effective residual throughout the distribution system
• Chlorine dioxide maintains its efficacy across a broader pH range and at higher water temperatures compared to free chlorine - both important factors in building water systems where pH can vary and hot water temperatures may fluctuate

ChloroKlean is particularly well-suited to HSG274 Part 2 compliance because its in-situ chlorine dioxide generation actively breaks down the biofilm that harbours Legionella. Rather than simply maintaining a chemical residual in the bulk water (which sodium hypochlorite alone does effectively), ChloroKlean addresses the root cause of persistent Legionella contamination in pipework systems.

HSG274 Part 3: other risk systems

Part 3 covers systems that do not fall neatly into Parts 1 or 2, including humidifiers, air washers, water features, vehicle washes, and other water systems that may create aerosols. The same principles of effective chemical treatment and biofilm control apply, and ChloroKlean's dual-action chemistry is equally relevant to these applications.

HSG282: spa pools and hot tubs

HSG282 - The control of Legionella and other infectious agents in spa-pool systems - was published in 2017 and is the definitive guidance for commercial spa pools, hot tubs, and similar systems. This includes spa pools in hotels, leisure centres, holiday parks, cruise ships, and display models.

HSG282 is specific about primary disinfection: it recommends that either chlorine or bromine is used as the primary residual disinfectant. The approved forms of chlorine include:

• Sodium hypochlorite (liquid)
• Calcium hypochlorite (granular/tablet)
• Sodium dichloroisocyanurate (stabilised chlorine)

Sodium hypochlorite is explicitly listed as an approved primary disinfectant under HSG282. This is directly relevant to ChloroKlean, because the sodium hypochlorite component of the formulation satisfies this primary disinfection requirement.

The chlorine dioxide generated in situ from the sodium chlorite component then provides supplementary benefits that HSG282 recognises as important challenges for spa pool operators:

• Biofilm control: HSG282 identifies biofilm as a significant risk factor in spa pool systems. Biofilm provides a protective environment for Legionella and other pathogens, making them resistant to standard disinfectant levels. Chlorine dioxide penetrates and breaks down biofilm in ways that sodium hypochlorite or bromine alone cannot.
• Consistent disinfection at higher temperatures: Spa pools operate at elevated temperatures (typically 30-40 degrees Celsius) where free chlorine degrades more rapidly. Chlorine dioxide is more stable at higher temperatures.
• Reduced disinfection by-products: HSG282 notes the importance of managing disinfection by-products. Chlorine dioxide does not produce trihalomethanes (THMs) or haloacetic acids (HAAs), unlike chlorine reacting with organic matter in spa pool water.

In practical terms, a spa pool operator using ChloroKlean is delivering HSG282-compliant primary disinfection through sodium hypochlorite, with the added capability of in-situ chlorine dioxide for biofilm management and enhanced pathogen control.

HSG179: swimming pool management

HSG179 - Managing health and safety in swimming pools - provides general guidance on health and safety management in swimming pool facilities. While it covers a broad range of safety topics (from poolside safety to water quality), the water treatment requirements align with the same principles as HSG282 and HSG274.

For swimming pools and hydrotherapy pools, the same advantage applies: ChloroKlean delivers approved primary disinfection chemistry (sodium hypochlorite) with the added benefit of chlorine dioxide for biofilm control and broader-spectrum pathogen efficacy.

BPR compliance: the regulatory layer

Beyond HSE operational guidance, all biocidal products used in the UK must comply with the GB Biocidal Products Regulation (GB BPR). ChloroKlean products are BPR-compliant, covering multiple product types:

Both sodium hypochlorite and chlorine dioxide generated from sodium chlorite are recognised active substances under the BPR framework. This means ChloroKlean's chemistry - both components - has regulatory approval for the applications covered by HSE guidance.

What this means in practice

For duty holders and facility managers, the HSE guidance framework can feel complex. The practical position with ChloroKlean is simple:

• ACOP L8 compliance: ChloroKlean provides effective, documented water treatment using chemistry that is recognised throughout the HSE guidance framework
• HSG274 compliance: Chlorine dioxide is explicitly referenced as an accepted treatment method for Legionella control in building water systems. The sodium hypochlorite base aligns with the most commonly used chemical treatment approach
• HSG282 compliance: The sodium hypochlorite component satisfies the primary disinfectant requirement. The in-situ chlorine dioxide provides additional biofilm and pathogen control
• BPR compliance: Both active substance components are approved under the GB Biocidal Products Regulation
• Documentation: Full safety data sheets, technical data sheets, and BPR compliance documentation are available, providing the audit trail that HSE guidance requires duty holders to maintain

ChloroKlean does not ask operators to step outside HSE-approved chemistry. It works within the established framework, using sodium hypochlorite as its foundation, and adds the proven benefits of in-situ chlorine dioxide generation for superior biofilm control and pathogen management.

For a free consultation on how ChloroKlean fits your compliance requirements, contact our team.