In an NHS hospital the water system has four named people sitting above it, and they are not interchangeable. The Authorising Engineer (Water) advises and audits. The Authorised Person operates. The Competent Person does the hands-on technical work. The Responsible Person carries the day-to-day duty. Confuse them and you get an audit finding, or worse.
HTM 04-01, NHS England’s guidance on safe water in healthcare premises, layers these roles deliberately so that the people who design the regime, the people who run it, and the person who independently checks it are not the same person marking their own homework [1]. That separation is the whole point. Below is how the hierarchy actually works, where it overlaps with the HSE’s L8 framework, and the failure modes I see most often.
The four roles, kept distinct
Start with the trap. Estates teams often collapse “Responsible Person” and “Authorised Person” into one job because the same individual frequently does both in a smaller trust. They are still separate functions with separate accountabilities.
The Authorising Engineer (Water), or AE(W), is the independent advisor. They are appointed by the trust to provide impartial advice, audit the water safety arrangements, assess the competence of the Authorised Persons, and report to the Water Safety Group. Crucially, the AE(W) does not operate the system or hold operational responsibility for it. Independence is their value [1]. If your AE(W) is also writing your operating procedures and then auditing them, you have lost the assurance the role exists to give.
The Authorised Person (Water), or AP, is the operational lead for the water systems. They take day-to-day managerial responsibility for the safe operation, implement the written scheme, hold the technical knowledge of the system, and direct or supervise the Competent Persons. The AP is appointed in writing by the duty holder, usually on the AE(W)‘s recommendation that they are competent.
The Competent Person (Water), or CP, does the technical tasks: flushing little-used outlets, taking temperatures, descaling and disinfecting TMVs, cleaning shower heads, sampling. They work under the direction of the AP and need defined training for the specific tasks they perform. The HSE’s L8 ACoP frames the broader legal duty to appoint a competent person to help manage legionella risk; HTM 04-01 sharpens it into this named operational rung [2].
The Responsible Person, often the duty holder’s appointee for legionella across the estate, holds the management duty for ensuring control measures happen and records are kept. In legionella terms this maps closely to the Responsible Person concept in L8 and HSG274 [2]. In a healthcare setting their work is co-ordinated through the Water Safety Group rather than done in isolation.
A model for who sits where
Picture the structure as four horizontal bands rather than a single chain of command.
At the top band sits the duty holder and the board — ultimately accountable under health and safety law, but not operating valves. Below them, a wide middle band is the Water Safety Group: a multidisciplinary committee chaired by a senior manager, with the Responsible Person, infection prevention and control, microbiology, estates, and the AP all feeding in. Running alongside that band, deliberately drawn as a vertical line touching every level but inside none of them, is the AE(W) — connected to the board for assurance, connected to the WSG for advice, but standing outside the operational chain so the independence holds. The bottom band is delivery: the AP directing, the CPs executing, contractors slotting in under the AP’s control.
The single most useful thing that diagram shows is the AE(W) as a side rail, not a rung. Draw them in the chain of command and you have misunderstood the role.
How the roles differ at a glance
| Dimension | AE(W) | Authorised Person | Competent Person | Responsible Person |
|---|---|---|---|---|
| Core function | Independent advice and audit | Operational lead | Hands-on technical tasks | Management of control regime |
| Independence | Required | No | No | No |
| Appointed in writing | Yes | Yes | Task-specific | Yes |
| Directs others | Advises, does not direct ops | Yes (directs CPs) | No | Co-ordinates via WSG |
| Sits in chain of command | No | Yes | Yes | Yes |
The table flattens nuance, so treat it as a map, not the territory. Trusts vary in how they title posts, and one person can legitimately hold more than one role provided the independence of the AE(W) is never compromised.
Trade-offs and failure modes
The recurring failure is false independence. An AE(W) drawn from the same contractor that delivers your flushing regime cannot credibly audit that regime. The pragmatic call is to check, at appointment, that there is no commercial or line-management thread between your AE(W) and your delivery side.
The second failure is competence drift at CP level. The role depends on task-specific training, and a CP cleared to take temperatures is not automatically cleared to disinfect a calorifier. When the AP cannot evidence what each CP was trained and authorised to do, the audit unravels fast.
The third is records. Every temperature reading, every flush of a dead leg, every TMV service is evidence that the regime is live. In my view this is where paper logs quietly fail healthcare estates: a missing month on a printed sheet looks identical whether the task was skipped or the page was lost. Moving temperature logs, task schedules and the asset register into a digital logbook makes the gap visible the moment it appears, which is precisely what the WSG and the AE(W) need to see.
A note on scope
This is general guidance on how the HTM 04-01 roles relate, not a competence assessment or a substitute for one. The exact appointments, the training each Competent Person needs, and the boundaries between overlapping posts must be set by your own site-specific risk assessment and your Water Safety Group, informed by a suitably qualified AE(W). Titles and structures also differ between trusts and across the devolved nations.
Where to start today
Pull your appointment letters and lay them against these four roles. If any role is unfilled, doubled up in a way that breaks AE(W) independence, or held verbally with no written appointment, you have your first action. From there, check that each Competent Person’s authorised task list matches what they are actually doing on the wards.
FAQ
Can the Estates Officer be the Responsible Person and the Authorised Person at once?
Often yes in practice, particularly in smaller trusts. The two operational roles can sit with one competent individual. What must not happen is for that same person to also act as the independent AE(W) auditing their own arrangements.
Does every healthcare site need its own AE(W)?
The AE(W) is engaged to provide independent advice and audit across the trust’s premises; they are typically appointed at organisation level rather than per building. Your Water Safety Group decides the scope, informed by HTM 04-01 [1].
Who chairs the Water Safety Group?
A senior manager with the authority to make things happen across estates and clinical services, not the AE(W). The AE(W) attends to advise and is kept outside the operational chair so their independent assurance stands.
Sources
[1] NHS England, “Health Technical Memorandum 04-01: Safe water in healthcare premises”. https://www.england.nhs.uk/publication/safe-water-in-healthcare-premises-htm-04-01/ [2] HSE, “Legionnaires’ disease. The control of legionella bacteria in water systems - ACoP and guidance (L8)”. https://www.hse.gov.uk/pubns/books/l8.htm