Legionella control under L8 and HSG274, with temperatures logged all year
In Great Britain, the HSE Approved Code of Practice L8 and technical guidance HSG274 set out how duty holders control Legionella in water systems: assess the risk, appoint a responsible person, write a scheme of control, implement it, monitor it and keep records. Aqueduct supplies continuous temperature and flow data at instrumented points, with drift and low use flagged. Your responsible person runs the scheme.
What L8 and HSG274 are and who they apply to
The Health and Safety Executive's Approved Code of Practice L8, Legionnaires' disease: the control of legionella bacteria in water systems, explains how employers and people in control of premises meet their legal duties to manage Legionella risk. HSG274 is the technical guidance that sits under it, in three parts: evaporative cooling systems, hot and cold water systems, and other risk systems. Together they apply to workplaces and premises with water systems where Legionella could grow and spread.
The duty holder must identify and assess the risk, appoint a competent responsible person, prepare a written scheme of control, put it into practice and keep records. For hot and cold water systems, HSG274 Part 2 describes temperature control, routine checks at sentinel outlets, flushing of little-used outlets and inspections. Healthcare premises follow further guidance such as HTM 04-01 in England. Check the current ACoP and guidance for the temperature limits and check frequencies that apply.
L8 and HSG274 duties and the evidence Aqueduct supplies
Aqueduct supplies continuous measurements. Your duty holder and responsible person own the scheme of control.
| Requirement | Evidence needed | How Aqueduct supplies it |
|---|---|---|
| Risk assessment | Understanding of the water system and where risk arises | The WaterGuard digital twin and flow data showing system layout, storage and low-use areas |
| Written scheme of control | Defined control measures and checks | Control points modeled in aQ Core with the limits your scheme sets |
| Hot water temperature control | Records of temperature at calorifiers, returns and sentinel outlets | Continuous temperature at instrumented points, with drift below your limit flagged |
| Cold water temperature control | Records that cold water stays cold at tanks and outlets | Continuous temperature on cold feeds and tanks where sensors are fitted, with warm periods flagged |
| Little-used outlets | Evidence of flushing or use | Flow data on branches showing use and no-use periods, so flushing can be targeted and confirmed |
| Cooling towers (HSG274 Part 1) | Monitoring of system operation and treatment | Make-up and bleed flow, conductivity where measured and fan and pump status from the BMS; water treatment testing stays with your contractor |
| Records | Records kept for the period the ACoP requires | Stored readings and exports by point, building and date range, with device health |
How to prepare Legionella records for an inspection
Check the risk assessment is current
Review it against the building as it is today, including any changes in use, occupancy or plant.
Instrument the scheme's key points
Fit temperature sensing at calorifier flows and returns, sentinel outlets and cold tanks, and flow sensing on low-use branches where practical.
Run continuous monitoring alongside rounds
Keep the manual checks your scheme requires, and let continuous data show what happens between them.
Act on drift
Route temperature and low-use alerts to the responsible person and record the action and the recovery reading.
Assemble the records
Export temperature histories, flushing evidence and corrective actions for the inspection period, next to your scheme and risk assessment.
What stays with your duty holder and responsible person
Legal duties stay with people. Aqueduct supplies measurements.
Risk assessment and scheme
A competent person assesses risk and writes the scheme of control.
Sampling and treatment
Legionella sampling, water treatment and disinfection are done by your team and specialist contractors.
Legal responsibility
The duty holder remains responsible. Aqueduct does not certify water systems as safe.
Related guidance
Often used alongside L8 and HSG274.
sites in 21 countries run on Aqueduct.
and 9 clinics in one of India’s top hospital chains.
US airport running water intelligence on Aqueduct.
of commercial real estate under Aqueduct.
FMCG manufacturing campus.
operations run on Aqueduct.
Related
Common questions
L8 is the HSE Approved Code of Practice on controlling Legionella bacteria in water systems. It explains the duties to assess risk, appoint a responsible person, control the risk and keep records. Aqueduct supplies continuous temperature and flow records at instrumented points.
HSG274 is HSE's technical guidance on Legionella control, in three parts covering evaporative cooling systems, hot and cold water systems and other risk systems.
Some organizations use continuous monitoring to support or partly replace manual checks, but the scheme of control and the responsible person decide. Aqueduct supplies the data and keeps the record.
Where flow is metered on branches, Aqueduct shows when outlets go unused, so flushing can be targeted and confirmed by the flow it creates.
No. Sampling and lab analysis stay with your team and accredited labs. Aqueduct supplies the operating data that helps explain results.
The duties apply to employers and people in control of premises where there is a risk, and the risk assessment decides what is needed. Check current HSE guidance for your premises.
HSG274 is technical guidance supporting legal duties in Great Britain. ASHRAE 188 is a US consensus standard for water management programs. The goals are similar, and Aqueduct supplies measurements for both.
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