Duty holders must assess the risk of legionella in their water systems, put a written control scheme in place, implement it, and keep records. Most of the actual control is temperature, turnover and cleanliness – and most failures come from dead legs and stored water nobody uses.
Who the duty falls on
Under the Health and Safety at Work etc. Act and the Control of Substances Hazardous to Health Regulations, employers and those in control of premises must assess and control the risk of exposure to legionella bacteria. The Health and Safety Executive’s Approved Code of Practice L8 and the associated HSG274 guidance set out how.
The duty holder is the employer, the person in control of the premises, or the self-employed person. It does not transfer to a contractor. You can appoint competent people to carry out the work – and you should – but the legal responsibility for it happening stays with you.
It applies to far more premises than people assume: offices, shops, pubs, restaurants, hotels, care homes, schools, gyms, salons, farms and landlords of residential property. The scale of what is required varies enormously with the risk, but the duty to assess does not.
For many small premises with a simple system, the assessment may conclude that the risk is low and that routine good practice is sufficient. That is a perfectly legitimate outcome – but it has to be a documented conclusion reached by assessment, not an assumption. The absence of an assessment is the breach, regardless of how simple the system is.
What creates the risk
Legionella bacteria are naturally present in water. They become a problem when three conditions come together: a temperature range that lets them multiply, stagnation or low turnover, and a means of creating breathable aerosol – a shower, a spray tap, a cooling tower, a hose.
- Water stored or circulated in the wrong temperature range. Too cool to be safe, too warm to be inert. Hot water stored below the recommended temperature, and cold water allowed to warm up, are the two classic failures.
- Dead legs and blind ends. A pipe to a fitting that was removed, or a branch to an outlet nobody uses. Water sits there indefinitely at room temperature. This is the single most common finding in commercial systems, and it accumulates over years of alterations.
- Little-used outlets. A shower in a rarely-used changing room, a tap in a store cupboard, a whole floor that is currently empty.
- Scale, sediment, biofilm and corrosion, all of which give bacteria somewhere to live and protect them from temperature and biocide.
- Cold water tanks that are uninsulated, unlidded, in warm plant rooms, or oversized for the actual demand so the water turns over slowly.
- Aerosol-generating equipment – showers, spray taps, humidifiers, cooling towers, vehicle washes, misting systems, and fountains.
In a hard water county, scale is a compounding factor – it gives biofilm somewhere to establish and it insulates the surfaces that temperature control relies on.
What the control scheme involves
| Element | In practice |
|---|---|
| Risk assessment | A written assessment of the system, the population at risk, and where control is needed. Reviewed periodically and whenever the system or its use changes |
| Schematic | An up-to-date drawing of the water system. Very few buildings have one, and producing it usually finds the dead legs |
| Written control scheme | What is monitored, how often, by whom, and what the action levels are |
| Temperature monitoring | Hot water at the sentinel outlets, cold water at the sentinel outlets, and stored temperatures – recorded, not just checked |
| Flushing regime | Little-used outlets run regularly, and recorded. The most commonly neglected element and one of the most effective |
| Tank inspection and cleaning | Cold water storage inspected, and cleaned and disinfected where the inspection requires it |
| TMV servicing | Thermostatic mixing valves serviced and their performance verified on schedule |
| Showerhead cleaning and descaling | Heads and hoses cleaned and descaled at defined intervals |
| Records | Kept and available. Inspectors and insurers ask for these, and so do prospective buyers of the building |
| Responsible person | A named, competent person with authority to act on findings |
The remedial work we carry out
Assessment identifies problems; plumbing resolves them. The work that usually follows an assessment:
- Removing dead legs. Cutting back redundant branches to the live main rather than capping them a metre away, which simply produces a shorter dead leg.
- Correcting temperatures. Raising stored hot water to the right temperature, insulating cold pipework so it stays cold, and separating hot and cold runs that have been strapped together.
- Fitting or servicing TMVs, so water can be stored hot enough while being delivered safely.
- Cold water tank work – lidding, insulating, screening, resizing where turnover is too slow, and cleaning and disinfecting.
- Pipework insulation, which is a temperature control measure as much as an energy one.
- Showerhead and hose replacement, and establishing a cleaning regime.
- Scale control, which in this region is a genuine contributor to biofilm.
- Chlorination and disinfection of systems and new pipework before it is brought into use.
We do the plumbing side and can carry out monitoring. Where a system is complex or high-risk enough to need specialist sampling and analysis, that is a water treatment specialist’s work and we will say so rather than stretching.
Where it goes wrong
- Buildings that changed use – an office converted to a gym, adding showers to a system never designed for them.
- Partially occupied buildings, where an empty floor’s pipework is stagnant and connected to the occupied system.
- Post-closure reopening. A building that stood empty needs its system flushing and, depending on the assessment, disinfecting before reoccupation. This is routinely skipped.
- Alterations that leave stubs. Every removed fitting is a potential dead leg if the branch is not cut back properly.
- Assessments that sit in a drawer. The assessment identifies actions. If nobody does them, the assessment is evidence that you knew.
- Records nobody keeps. Monitoring that happens but is not recorded is, for enforcement purposes, monitoring that did not happen.
Reopening a building that has stood empty? Flushing and, depending on risk, disinfection come before reoccupation, not after.
Questions we get asked about this
Do we legally need a legionella risk assessment?
If you are an employer or in control of premises, you must assess the risk from your water systems. For a small, simple system the assessment may conclude the risk is low and routine good practice suffices – but the assessment itself has to exist and be documented.
How often should it be reviewed?
Periodically, and whenever there is reason to think it is no longer valid – a change to the system, a change of use, a change in occupancy, or a case of illness. A two-year cycle is common practice for stable systems.
Does this apply to landlords of residential property?
Landlords have a duty to assess and control the risk in the properties they let. For a typical domestic system with a combi boiler and no stored water, the risk is usually low and the assessment straightforward – but it should still be done and recorded.
What is a dead leg?
A length of pipe where water sits without moving – a branch to a removed fitting, or to an outlet nobody uses. It is the most common finding in commercial systems, and the fix is to cut it back to the live pipework rather than capping it short.
What temperatures should our system run at?
The guidance sets out target temperatures for stored hot water, for hot water at outlets, and a maximum for cold water, with specified times for reaching them at the tap. The important thing is that they are monitored at sentinel outlets and recorded, not just assumed.
Can you do the risk assessment as well as the remedial work?
We can carry out assessment and monitoring for straightforward systems, and the remedial plumbing in all cases. For complex or high-risk systems requiring specialist sampling and analysis, that is a water treatment specialist’s role and we will tell you.
Sources
- HSE, Legionnaires’ disease: The control of legionella bacteria in water systems (ACOP L8) and HSG274 — https://www.hse.gov.uk/legionnaires/
Regulations and standards referenced on this page
- Legionnaires’ disease: the control of legionella bacteria in water systems (Approved Code of Practice L8) — Health and Safety Executive
- HSG274: Legionnaires’ disease – technical guidance — Health and Safety Executive
What happens when you call
Call and describe it
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We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
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The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
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