What is the difference between HTM 04-01 and HSG274?
On this page
Key points
- HSG274 is the general guidance for controlling legionella in all premises; HTM 04-01 is the healthcare-specific layer on top of it.
- The headline technical difference: hot water at 50°C at outlets under HSG274, 55°C under HTM 04-01; storage at 60°C under both.
- HTM 04-01 adds structure: a water safety plan, a multidisciplinary water safety group, and named roles including an independent Authorising Engineer.
- HTM 04-01 Part C adds pseudomonas controls for augmented care, which HSG274 does not cover at all.
- Same law underneath. Both are routes to satisfying HSWA and COSHH; the difference is the standard expected for the occupants.
HSG274 is the HSE's general technical guidance on controlling legionella, and it applies to every kind of premises. HTM 04-01, Safe water in healthcare premises, is the healthcare-specific guidance published for NHS trusts and similar estates, and it tightens almost everything HSG274 asks for. If you run a hospital, HTM 04-01 is your working document; if you run anything else, HSG274 is.
Both are covered in depth on HSG274 explained and HTM 04-01 explained. This page is the comparison: what exactly changes when you move from the general regime to the healthcare one, and how to tell which side of the line your building sits on.
The two regimes compared
| HSG274 | HTM 04-01 | |
|---|---|---|
| Published by | Health and Safety Executive | Department of Health and Social Care (NHS estates guidance) |
| Applies to | All premises: landlords, offices, schools, hotels, most care settings | Healthcare premises: NHS trusts, hospitals, similar estates |
| Hot water at outlet | At least 50°C within one minute | At least 55°C within one minute |
| Management framework | Risk assessment, written scheme of control, competent responsible person | Formal water safety plan owned by a multidisciplinary water safety group |
| Named roles | Duty holder and responsible person; competence is the test | Duty Holder, Responsible Person (Water), Authorised Person (Water), independent Authorising Engineer (Water) |
| Pseudomonas | Not covered | Part C: dedicated controls for augmented care, including outlet sampling |
| TMV regime | Serviced at the interval the risk assessment sets | Tighter, specified commissioning and in-service checks |
Why healthcare gets a stricter regime
The logic is vulnerability, and it runs through every difference in the table. A hospital concentrates people who are elderly, immunosuppressed, post-surgical, or on invasive devices, precisely the people a waterborne infection hits hardest. So the margins widen: the outlet temperature target rises by five degrees to shrink the zone where water can drift into the 20 to 45°C growth range; the management framework becomes a formal water safety plan with a named group rather than resting on one responsible person; and an independent Authorising Engineer is built in to audit the arrangements from outside the chain of command, a second opinion general premises are not required to have.
Part C is the clearest illustration. HSG274 is a legionella document. HTM 04-01 accepts that in augmented care units the threat list is longer, Pseudomonas aeruginosa above all, and adds outlet sampling and point-of-use controls that simply do not feature in the general guidance. The comparison of the two organisms is set out in legionella versus pseudomonas.
Which regime does your building fall under?
The dividing line is clinical function, not the word "care" in the building's description. Hospitals and NHS estates sit squarely under HTM 04-01. A standard residential or nursing care home usually manages water safety under HSG274 and ACOP L8, as our care homes guide explains, though the resident population means its risk assessment must take vulnerability seriously. Settings that blur the line, hospices, specialist units, community hospitals, should look at how much of their activity resembles a hospital ward and take advice accordingly, because regulators will judge them against the regime that matches their function.
The temperature difference is five degrees, but the real difference is five layers: higher targets, a water safety plan, a named group, independent audit, and pseudomonas controls. Healthcare water safety is the general regime with every margin widened.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
What stays the same
For all the differences, the spine is identical, because both documents exist to satisfy the same law. Hot water is stored at 60°C and cold kept below 20°C. Little-used outlets are flushed weekly. Monitoring is scheduled and every check is recorded, with records kept for at least five years. And neither document certifies anything: they structure a continuing duty to assess, control, and evidence. Whether your targets come from HSG274 or HTM 04-01, the temperature checker will tell you whether your readings meet them, and a log book is where the proof lives. The temperature chart shows both sets of figures side by side.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
Frequently asked questions
What is the difference between HTM 04-01 and HSG274?
HSG274 is the HSE's general technical guidance on controlling legionella, used in offices, rented property, and most other buildings. HTM 04-01 is the healthcare-specific guidance, Safe water in healthcare premises, applied to NHS trusts and similar estates. HTM 04-01 is more demanding: hot water must reach 55°C at the outlet rather than 50°C, a formal water safety plan and multidisciplinary water safety group are required, named roles including an independent Authorising Engineer (Water) are defined, and Part C adds Pseudomonas aeruginosa controls for augmented care. Both sit under the same legal duty.
Does a care home follow HTM 04-01 or HSG274?
A standard residential or nursing care home generally works to HSG274, the general guidance, within the ACOP L8 framework, although the vulnerable resident population means the risk assessment must reflect that. HTM 04-01 is written for healthcare premises, primarily hospitals and NHS estates. The dividing line is the clinical character of the setting: the more the premises functions as a hospital delivering care to acutely ill or immunosuppressed people, the more the HTM 04-01 regime applies.
Why is the hot water temperature different in HTM 04-01?
HSG274 expects hot water to reach at least 50°C at the outlet within one minute. HTM 04-01 raises that to 55°C at the outlet within one minute for healthcare premises, while storage stays at 60°C. The higher target gives a bigger safety margin against the legionella growth range, reflecting the greater vulnerability of patients. It also sharpens the scalding conflict, which is why thermostatic mixing valves at outlets, with their own servicing regime, are central to the healthcare approach.
Is HTM 04-01 a legal requirement?
Not directly. HTM 04-01 is guidance, like HSG274, and creates no new law. The legal duty comes from the Health and Safety at Work Act and COSHH. But within the NHS, HTM 04-01 is the expected standard, and it is how a healthcare organisation demonstrates that it has met the legal duty in a high-risk setting. A hospital that ignored it would need very strong evidence that its alternative arrangements controlled the risk equally well.
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