Short answer: HSE's HSG274 Part 2, Table 2.1, sets the usual rhythm: calorifier flow and return and hot and cold sentinel outlets monthly; shower heads and subordinate loop returns quarterly; calorifiers, cold water tanks and insulation yearly; little-used outlets flushed weekly. The building's own risk assessment sets the actual frequencies and can change them (para 2.79).
Where these checks come from
HSG274 is HSE's technical guidance on Legionnaires' disease. Part 2 covers hot and cold water systems. It gives practical advice on the Health and Safety at Work etc Act 1974, the Control of Substances Hazardous to Health Regulations 2002 and the Management of Health and Safety at Work Regulations 1999. The copy on hse.gov.uk is the second edition, published 2024; HSE notes that only Part 1 was changed in that edition.
It sits under the Approved Code of Practice, L8 (fourth edition, 2013). The two have different status. HSE says following the guidance "is not compulsory", but if you do "you will normally be doing enough to comply with the law". The ACOP has "a special legal status": if you are prosecuted and did not follow it, you have to show you complied in some other way.
Table 2.1 is "a checklist for hot and cold water systems with an indication of the frequency of inspection and monitoring". The paragraph above it adds that "the risk assessment should define the frequency of inspection and monitoring depending on the type of use and user" (para 2.79).
The checklist, task by task
| Plant or service | Check | Target | Frequency in Table 2.1 |
|---|---|---|---|
| Calorifiers | Flow temperature | As close to 60 °C as practicable, not below 60 °C | Monthly |
| Calorifiers | Return temperature | Not below 50 °C | Monthly |
| Calorifiers | Inspect internally (hatch or boroscope) and clean by draining; with no hatch, purge debris from the base | – | Annually, or as the rate of fouling indicates |
| Calorifiers and hot water heaters | Collect the first flush from the base and look at clarity, debris and temperature | – | Annually, more often if the risk assessment or findings say so |
| Hot water, non-circulating | Sentinel outlets: nearest, furthest and long branches | At least 50 °C within one minute (55 °C in healthcare premises) | Monthly |
| Hot water, circulating | Return legs of principal loops (pipe surface readings allowed on metal pipe) | At least 50 °C (55 °C in healthcare premises) | Monthly |
| Hot water, circulating | Return legs of subordinate loops, or the last outlet on each loop | Over 50 °C within one minute at the outlet (55 °C in healthcare premises) | Quarterly, ideally on a rolling monthly rota |
| Point-of-use heaters (up to 15 litres) | Water temperature, or confirm a high turnover | 50–60 °C (55 °C in healthcare premises) | Monthly to six-monthly, or as the risk assessment says |
| Combination water heaters | Outlet temperature; header tank inspected with the cold tanks | 50–60 °C | Temperature monthly; header tank annually |
| Cold water tanks | Inspect and carry out remedial work | – | Annually |
| Cold water tanks | Stored water temperature away from the ball valve, and the incoming mains | – | Annually (summer), or as temperature profiling indicates |
| Cold water services | Sentinel taps: nearest and furthest from the tank, plus key branches | Below 20 °C within two minutes | Monthly |
| Cold water services | Thermal insulation intact | – | Annually |
| Showers and spray taps | Dismantle, clean and descale heads, inserts and hoses | – | Quarterly, or as fouling or other risk factors indicate |
| Infrequently used outlets | Flush outlets not used for seven days or more until the temperature stabilises | – | Weekly, or as the risk assessment says |
| Thermostatic mixing valves | Risk assess whether each valve is needed and remove it if not; where needed, inspect, clean, descale and disinfect strainers and filters | – | Annually or as the risk assessment says, taking account of the manufacturer |
| Expansion vessels | Flush through and purge to drain where practical; change bladders as the manufacturer or the risk assessment says | – | Monthly to six-monthly, as the risk assessment says |
| Base exchange softeners | Salt level and hardness check | – | Weekly, depending on vessel size and salt use |
Table 2.1 also has rows for point-of-use filters, softener servicing, multiple-use filters and rotating checks on other outlets to build a temperature profile. Read the full rows in the source before writing a method statement.
Sentinel outlets
In a simple cold water system the sentinels are "typically the furthest tap (far sentinel) and the nearest (near sentinel) to the supply or storage tank". HSE adds that "the layout of the distribution system should be considered rather than the location of the outlet" (para 2.59). Bigger systems have several far sentinels, such as the end of each riser, and any part of the system the near and far sentinels do not represent needs its own monitored outlet (para 2.59). In a hot system without circulation the sentinels are the taps nearest and furthest from the calorifier, plus the outlets at the ends of significant spurs (para 2.62). In a circulating hot water system the far sentinels are the return legs towards the end of each loop (para 2.63). Subordinate loops are tested so that all of them are covered each quarter (para 2.64).
The temperature regime
Where temperature is the control, hot water "should be stored at a minimum of 60 °C and distributed so it reaches a minimum temperature of 50 °C (55 °C in healthcare premises) within one minute at outlets" (para 2.82). Healthcare premises should also refer to Health Technical Memorandum 04-01, and care homes and other high-risk settings need particular consideration in the risk assessment (para 2.2).
Where a thermostatic mixing valve (TMV) is fitted, the outlet delivers blended water, typically between 38 °C and 46 °C (para 2.74). A reading at that spout cannot show whether the hot supply reaches 50 °C, so the written scheme should say where the reading for that outlet is taken. For legionella sampling, HSE says to use separate hot and cold outlets, not outlets downstream of TMVs (para 2.121).
Worked example: a three-storey office
The plant: one calorifier with a pumped return, two principal hot water loops and four subordinate loops, a cold water storage tank in the roof plant room, two showers, and a cleaner's sink used about once a fortnight. The building's risk assessment adopts the Table 2.1 frequencies unchanged. A contractor's plan could look like this:
- Every month: calorifier flow and return; return legs of both principal loops; cold sentinels nearest and furthest from the tank; one subordinate loop, so all four are covered each quarter on a rolling rota.
- Every 3 months: strip and descale both shower heads and hoses.
- Every 12 months: calorifier inspection and drain-down; first flush from the base; cold water tank inspection; tank and mains temperatures in summer; insulation check; mixing valve strainers, if any are fitted.
- Every week: flush the cleaner's sink while it goes unused for seven days or more. A weekly contractor visit rarely makes sense, so this is usually agreed with someone on site and logged there. HSE says that once started, the procedure "has to be sustained and logged" (para 2.78). Ask the assessor whether the sink could be removed instead and its pipe cut back (para 2.77).
If the building housed a high-risk population, such as a care home, HSE says "more frequent flushing may be required as indicated by the risk assessment" (para 2.78).
Who does what
- The dutyholder is the employer, a self-employed person, or whoever is in control of the premises or systems in connection with work (L8, para 28). They make sure the risk assessment is done and appoint a competent person to help (L8, para 48).
- The responsible person is the competent person appointed to take day-to-day responsibility for controlling the risk (L8, para 51).
- The maintenance contractor often carries out the monitoring. L8 allows this: it can be done by "an external contractor or an independent third party" (para 65). Work to the frequencies in that building's risk assessment and written scheme, not a generic list.
- Site staff usually do the weekly flushing, because it falls between monthly visits.
Hiring a contractor "does not absolve the dutyholder of responsibility" (L8, para 57).
What to record, and for how long
L8 lists what records should include, among them "the results of any monitoring inspection, test or check carried out, and the dates" (para 71). Keep monitoring records "for at least five years". Keep the other records, such as the risk assessment and written scheme, "throughout the period they are current and for at least two years afterwards" (para 72).
For each reading, record:
- the outlet or plant item, described well enough for the next person to read the same point, and whether it is a near or far sentinel;
- the date;
- the temperature and how long the water ran before it was reached;
- who took the reading, verified by a signature or an electronic equivalent (HSG274 Part 2, para 2.54);
- any action taken, and who it was reported to.
Our Legionella monthly temperature log template sets this out as a table and a CSV file.
When the risk assessment needs a review
L8 sets no fixed number of years. It says to review the assessment "regularly and specifically whenever there is reason to suspect it is no longer valid" (para 47), for example after changes to the system or the building's use, or when checks show the controls are no longer working. A run of monthly readings below target is exactly that kind of evidence. Read more in Legionella risk assessment review: how often and what triggers one.
Running these checks in Field Suite
- Contracts: a maintenance contract holds visits that repeat every set number of months, each with a form attached. A job to book is created a set number of days before each visit is due. Monthly, quarterly and yearly checks fit this directly. Weekly flushing does not: contract visits are set in whole months, so the weekly log stays with the site.
- Build your own temperature log in the form builder: Field Suite has no ready-made Legionella form. Use number fields with a unit (°C, seconds), a repeating group for each outlet, and a pass/fail question for each reading. A fail answer marks the form failed and alerts the office. Number fields do not fail on a limit by themselves, so the engineer answers the pass/fail question against the target.
- Equipment register: calorifiers, tanks and vessels listed at each site, with their service interval and job history. Signed forms are kept as PDFs with the job.
See planned maintenance software and pump and water services software, read booster set servicing, or book a demo.
Questions
Is Table 2.1 a legal requirement?
No. HSG274 is guidance: following it is not compulsory, but if you do you will normally be doing enough to comply with the law. The legal duties come from the Health and Safety at Work etc Act and COSHH, with L8 as the Approved Code of Practice.
Can the risk assessment set different frequencies?
Yes. HSE says the risk assessment should define the frequency of inspection and monitoring, depending on the type of use and user (HSG274 Part 2, para 2.79). Some rows, such as point-of-use heaters and expansion vessels, give a range for that reason.
What does "within one minute" mean for hot outlets?
Run the outlet and read the temperature: it should reach at least 50 °C within one minute (55 °C in healthcare premises). For cold outlets the target is below 20 °C within two minutes (Table 2.1).
Do we need to sample for legionella every month?
Table 2.1 is about temperature checks, inspection and cleaning. Whether sampling is needed is a separate decision for the risk assessment; HSE's landlord guidance says testing "should not be confused with temperature monitoring".
Field Suite is job management software, not a water hygiene consultancy. The building's own risk assessment and written scheme decide what is checked and how often.
Sources
- HSE, Legionnaires' disease: Technical guidance, HSG274 Part 2: The control of legionella bacteria in hot and cold water systems (second edition, 2024), paras 2.2, 2.54, 2.59, 2.62, 2.63, 2.64, 2.74, 2.77, 2.78, 2.79, 2.82, 2.121 and Table 2.1. https://www.hse.gov.uk/pubns/priced/hsg274part2.pdf
- HSE, HSG274 publication page. https://www.hse.gov.uk/pubns/books/hsg274.htm
- HSE, L8 Legionnaires' disease: The control of legionella bacteria in water systems, Approved Code of Practice and guidance (fourth edition, 2013), paras 28, 47, 48, 51, 57, 65, 71 and 72. https://www.hse.gov.uk/pubns/priced/l8.pdf
- HSE, Legionella and landlords' responsibilities. https://www.hse.gov.uk/legionnaires/legionella-landlords-responsibilities.htm
Last checked: 5 November 2026 against the sources above.
Field Suite is job management software for UK building services firms, not a consultancy. Your own risk assessments, contracts and advisers decide what applies to your work. Spotted a mistake? Email info@fieldsuiteapp.com and we correct it.