HSG274 Part 2 2024 Changes: The Complete Guide for Assessors

The 2024 edition of HSG274 Part 2 brought the most significant changes to legionella guidance in over a decade. For qualified risk assessors carrying out risk assessments, these changes affect what you assess, how you report, and what you recommend.

This guide covers every significant change in the 2024 edition, with practical guidance on what each one means for your assessments.

Why the update matters

HSG274 Part 2 was last substantially revised in 2014. In the decade since, the industry learned from outbreaks, enforcement action, and advances in water treatment technology. The 2024 edition reflects these lessons. Assessors who continue to work from the 2014 edition risk producing assessments that are no longer aligned with current HSE expectations.

The 2024 edition took effect immediately upon publication. There is no transition period. Assessments carried out after the publication date should reflect the new guidance.

Scalding risk assessment

One of the most significant additions in the 2024 edition is the requirement to consider scalding risk alongside legionella risk. Previously, scalding was treated as a separate issue. The 2024 edition makes it clear that the two risks must be balanced within a single assessment.

This means assessors must now:

• Identify areas where vulnerable persons are at risk of scalding (care homes, hospitals, schools, nurseries)
• Assess whether TMVs are fitted and appropriate in those locations
• Consider the impact of TMV installation on legionella risk -- TMVs can create warm water conditions downstream that favour bacterial growth
• Recommend a TMV maintenance programme as part of the legionella control scheme

The key tension is that lowering water temperatures to prevent scalding can increase legionella risk, and vice versa. The 2024 edition expects assessors to navigate this trade-off explicitly.

Solar thermal and renewable heating systems

The 2024 edition includes new guidance on solar thermal heating systems and heat pumps. These systems were barely mentioned in the 2014 edition, but their increasing prevalence made updated guidance necessary.

Key points:

• Solar thermal systems can produce variable water temperatures, particularly in periods of low solar gain
• Assessors must check that stored water reaches 60 degrees C regardless of the heat source
• Backup heating must be adequate to maintain safe temperatures when solar gain is insufficient
• Heat pump systems that store water below 60 degrees C require additional controls or treatment

Point-of-use water heaters

The 2024 edition provides clearer guidance on instantaneous water heaters (combi boilers, electric point-of-use heaters). The previous edition was ambiguous about whether these systems required the same assessment rigour as stored water systems.

The 2024 edition clarifies:

• Instantaneous heaters that do not store water are generally lower risk
• However, they must still be assessed for dead legs, infrequent use, and downstream risks
• Systems with small internal storage volumes (even a few litres) should be treated as stored water systems

Incident planning and response

The 2024 edition places greater emphasis on incident planning. Assessors are now expected to check whether the duty holder has:

• A documented incident response plan for suspected legionella cases
• A communication procedure for notifying the responsible person, the HSE, and local public health authorities
• Pre-arranged access to specialist cleaning and disinfection services
• A procedure for managing the water system during and after an incident

This moves incident planning from a "nice to have" to an expected part of the control scheme.

Enhanced record-keeping requirements

The 2024 edition is more prescriptive about what records must be kept and how they should be maintained. Specifically:

• Records must be kept for a minimum of five years (previously guidance was less specific)
• Electronic records are explicitly acceptable, provided they are secure and accessible
• Records should include not just monitoring results but also evidence that results have been reviewed and acted upon
• The responsible person should sign off on monthly and quarterly monitoring reviews

Updated Table 2.1 monitoring frequencies

Table 2.1, which sets out the minimum monitoring and inspection frequencies, was updated in the 2024 edition. The key changes include:

• Monthly TMV checks are now explicitly required (previously implied)
• Six-monthly cold water tank inspections are clarified as a minimum
• The annual risk assessment review is now framed as a requirement, not just good practice
• New entries for solar thermal and heat pump system checks

Little-used outlets and building closures

The 2024 edition provides more detailed guidance on managing infrequently used outlets and buildings that have been temporarily closed (a lesson from the COVID-19 pandemic). Key additions:

• A clear definition of "infrequently used" as any outlet not used at least weekly
• Recommissioning procedures for buildings that have been closed for extended periods
• Flushing requirements before and after periods of non-use
• The need to re-assess the risk if a building's occupancy pattern has changed significantly

What assessors should do now

If you are a qualified assessor, here is what you should do in response to the 2024 changes:

1. Read the full 2024 edition -- do not rely on summaries alone
2. Update your assessment template to include the new conditions (scalding risk, solar thermal, incident planning)
3. Review your standard recommendations to ensure they align with the updated guidance
4. Brief your clients on the key changes, particularly around scalding risk and incident planning
5. Check your CPD -- ensure your training reflects the 2024 edition

L8Pro was updated to reflect all 2024 changes from day one. The 67 risk conditions in L8Pro include every new requirement from the 2024 edition, including scalding risk assessment, solar thermal checks, and incident planning.