How do you know your Legionella Written Scheme complies with the law?

Previous articles I have written have shown the importance of ensuring your Written Scheme complies with the guidance provided in HSG 274 so this article is asking about wider compliance.

The HSE look at what constitutes good practice and on how relevant application of good practice contributes to the duty to reduce risks ‘so far as is reasonably practicable’ (SFAIRP) or demonstrate that risks have been reduced ALARP. In other words will your Legionella Written Scheme, or Water Safety Plan, reduce risks on site.

HSG 274 requires that we employ “good practice” to reduce risks, but what is good practice? Good practice is the generic term for those standards for controlling risk which have been judged and recognised by HSE as satisfying the law when applied to a particular relevant case in an appropriate manner.

This may take many forms. The scope and detail of good practice will reflect the nature of the hazards and risks, the complexity of the activity or process and the nature of the relevant legal requirements.

Examples of good practice will include:

  • Approved Codes of Practice (e.g.ACoP L8)
  • HSE Guidance (e.g. HSG274 and HSG282)
  • Standards produced by Standards-making organisations (e.g. BS, CEN, CENELEC, ISO, IEC, of which there are thousands of documents)
  • Guidance agreed by a body (e.g. trade federation, professional institution, sports governing body) representing an industrial/occupational sector (e.g. the Legionella Control Association or the Water Management Society).

Good practice may change over time because of technological innovation which improves the degree of control (which may provide potential to increase the use of elimination and of engineering controls), cost changes (which may mean that the cost of controls decreases) or because of changes in management practices.


Good practice may also change because of increased knowledge about the hazard and/or a change in the acceptability of the level of risk control achieved by the existing good practice.


In the definition of good practice, ‘law’ refers to that law applicable to the situation in question; such law may set absolute standards or its requirements may be qualified in some way, for example, by ‘practicability’ or ‘reasonable practicability’.

‘Good practice’, as used by HSE, can be distinguished from the term ‘best practice’ which usually means a standard of risk control above the legal minimum.

In judging compliance, HSE expects duty-holders to apply relevant good practice as a minimum. For new plant/installations/situations, this will mean the application of current good practice. For existing plant/installations/situations, this will mean the application of current good practice to the extent necessary to satisfy the relevant law.

Compliance with relevant good practice alone may be sufficient to demonstrate that risks have been reduced ALARP, it is also possible that meeting good practice alone may not be sufficient to comply with the law.

Duty-holders need to:

  1. review their accident scenarios and risk management arrangements (for prevention, control and mitigation);
  2. identify what good practice is relevant;
  3. comply with the good practice (to the extent to which it is applicable);
  4. ask the question – are there any other measures which would be effective in further reducing the risks?
  5. determine whether the extra measures are reasonably practicable and implement those that are.

In determining what is reasonably practicable, the starting point for the risk/sacrifice calculation should be the current situation. Duty-holders should also consider the adequacy of the relevant good practice. When a code or standard is updated to a higher standard, the plant, installation or situation should be examined to see if it can be brought up to the new standard. Any such upgrades should be undertaken if reasonably practicable.

So you should always review your Legionella Written Scheme and check to see whether it complies with both the relevant HSE guidance but also any other good practice is available.

If you want to have your existing Legionella Written Scheme checked to see if it is suitable and sufficient or indeed if you want a Written Scheme creating then contact Collaton Consultancy Limited via

(parts of this article have been précised from the HSE website)



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