Jargon buster – phrases and acronyms such as ‘WSP’, ‘Written Scheme’, RP & AP and Water Safety Group, what do they all mean?
In this blog, we explain some of the more popular phrases and acronyms being used. To make this more fun, and to help test your knowledge, we’ve created a crossword containing terms used in this and previous blogs, along with general industry terms.
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Common Water Hygiene Terms
Water Safety Plan (WSP) and Legionella Written Scheme of Control (WSC), these terms are often used interchangeably to describe a method of control that can be used to ensure the provision of safe water (including waterborne pathogens (Legionella and Pseudomonas aeruginosa) and other water-related risks, i.e. temperature (scald)).
Legionella Guidance
WSP & WSC are referenced in HSG274 Part 2, and WSP is referenced in the HTM 04-01. These guidance notes provide aid on how to comply with all aspects of water management, including management policy, Legionella risk assessment, water hygiene schematics, operational procedures, and logbooks. WSP is a term used primarily in the healthcare sector, although this does not preclude any organisation from adopting the term when developing its own control documentation.
Legionella Written Scheme of Control (WSC)
The WSC acts as an operational guide on the control measures necessary to ensure the correct operation of a water system. The objective is that once the risk of Legionella has been identified and evaluated, measures are implemented to mitigate the potential proliferation of Legionella bacteria in the hot and cold-water systems. Those systems are specific to the systems identified within the risk assessment. The WSC should include the following details:
- Management Structure – a defined ‘communications pathway’ for all involved in the control regime (i.e. Responsible Person (RP), Authorised Person (AP), independent Authorising Engineer Water (AEW)), their roles and duties;
- Legionella Risk assessment – The need for, specification and review criteria;
- Schematic drawing – to be up to date, shows the layout of the system within and around the premises, all outlets, all pipe routes, storage header tanks and domestic hot water generators, including relevant items of plant;
- Define correct and safe operation of each water risk system;
- Precautions and actions to be taken to prevent and minimise the risk associated with each risk system;
- Details of tests and checks – operational/performance checks, including their frequency and acceptable control parameters, microbiological testing, TVC, (In water testing, TVC stands for Total Viable Count, which is a measurement of the total number of live microorganisms (like bacteria, yeast, and mould) in a water sample. This non-selective test provides a general indicator of overall water quality and the level of microbial contamination present, offering a "health check" for the water system.
- Remedial actions – when a water risk system is identified as being out of control, this details the actions to be taken to return the system to control.
- Incident planning – such occurrences as loss of mains water, loss of control, i.e. temperature control, repeated high counts of Legionella, an outbreak of legionellosis (confirmed at site and source yet to be confirmed).
Water Safety Plan (WSP)
Those organisations with existing robust water management arrangements in place will have much of the WSP established. That said, the WSP essentially includes the above elements/components of the WSC, although the HTM04-01 contains additional details:
Content of the WSP will depend on the size and complexity of the water system/s;- Governance Arrangements – WSG (Water Safety Group) membership, remit, terms of reference (ToR), training competency for all staff levels of those involved in the control regime;
- It is a living document kept under review by the WSG;
- Cross-referenced with the healthcare organisation’s security management strategy and business continuity plan;
- Clinical/bacterial and engineering risk assessments are completed to identify those who are significantly at risk and the type of water risk systems that exist;
Water Safety Group (WSG)
The WSP details the WSG, which is a multidisciplinary group. Group members will often represent: estates, infection control, microbiology, health and safety and projects & design, so that both clinical and non-clinical concerns are suitably addressed, which in turn support a well-balanced approach to water safety.
The WSG, with support from the appointed AE(W), will also collectively agree upon the content of the WSP, which will be informed by risk assessments to aid the WSG in determining the appropriateness and suitability of the contents. The outcome of those risk assessments should be suitably quantified, and the WSG should review any recommendations to ensure agreed deadlines remain on schedule.
WSG members need to have their roles and responsibilities relevant to an individual’s position within the organisation defined within the WCS/WSP, along with a Communications Pathway showing the hierarchy of management control.
For example, the Duty Holder (DH) would typically be the Chief Executive, the Designated Person (DP) would generally hold a directorship (not necessarily water-related, such as the Finance Director), and the Head of Estates may be the Responsible Person (RP).
Whilst the majority of legal responsibility resides with the DH (Duty Holder), management and operational responsibility is often devolved to the RP. The RP is then supported by an Authorised Person/s (AP) – who is/are competent to execute the daily operational control of the water risk systems, as defined in the WSP.
Water Safety Audit
A continuous process – typically completed in partnership with an independent AE(W) to evaluate the performance of the WSG and to ensure the WSC/ WSP are being implemented appropriately.
In summary, numerous phrases and acronyms are used, some of which are similar. The guidance documents define these phrases and acronyms. In this blog, we’ve taken these and explained them further, highlighting the differences between various types of organisations.
Further reading is available> What is a Water Safety Plan and why have one?
Feel free to reach out if you have any questions about the issues mentioned above or if you would like to consult with one of our experts on water hygiene.
Editor's Note: The information provided in this blog is correct as of the date of original publication - January 2018. (Revised December 2025)
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