The risk assessment finds the problem. The written scheme of control is what fixes it and keeps it fixed, and it is the document that turns a report into a regime. HSE's L8 Approved Code of Practice expects a duty-holder who has identified a risk to prepare one, appoint somebody to manage it, and keep records showing it was followed.
What the legionella written scheme contains
An up to date schematic of the system. The control measures for each part of it, whether temperature, biocide or physical. Who monitors what, how often, and to what acceptable range. What to do when a reading falls outside that range, written down in advance. The cleaning and disinfection regime for tanks, showers and TMVs. And the review arrangements. A scheme that names no person and no frequency is a description, not a scheme.
Who the responsible person is
The duty-holder appoints a person to take managerial responsibility and to ensure the scheme is implemented, with enough authority and knowledge to do it. In a small business that is often the owner; in a managed building it is usually the facilities manager. Naming somebody who has neither the time nor the authority is the most common way for a good scheme to stop happening within a year.
What the records have to show
The monitoring readings with dates and the person who took them. Remedial actions taken and when they were completed. Cleaning and disinfection certificates. Changes to the system. Reviews of the assessment. Records like these are what make the difference between a system that is controlled and one that is merely believed to be, and they are the first thing an inspector reads after a case.
Legionella flushing, and when it becomes the main control
Where outlets are little used, flushing them on a defined schedule is the control that keeps water moving. It has to be recorded like any other check, and it has to be done in a way that avoids creating aerosol. In a partly occupied building it is often the single most important thing in the scheme, and it is also the one most quietly dropped when somebody is on holiday.
Legionella remediation: remedial work, cleaning and disinfection
Removing dead legs, insulating cold pipes away from heat, correcting calorifier temperatures, replacing unsuitable materials, cleaning and descaling shower heads and hoses, and cleaning and chlorinating tanks. After significant work or a positive sample, disinfection to the recognised method is normally followed by sampling to confirm it worked, which is one of the cases where sampling is genuinely warranted.
How often should legionella testing be done, and how often monitoring
The scheme sets both frequencies and they are not the same number. Monitoring is the regular one: sentinel outlet and calorifier temperatures monthly, little used outlets flushed on their own schedule, tanks and shower heads inspected at the interval the assessment named. Sampling has no universal interval, because for most domestic hot and cold water systems HSE does not expect sampling at all. Where it is warranted the frequency comes from the system rather than the calendar: routinely on cooling towers and evaporative condensers, on any system controlled by biocide instead of temperature, in healthcare and other settings with highly susceptible people, and as often as it takes to close out a period when the control measures were not being achieved. A scheme that names a sampling interval and cannot say which of those it is answering has copied somebody else's scheme.
Legionnaires testing requirements, and what the scheme has to say about them
There is no general requirement to test water for legionella, which surprises people who have been sold sampling. The requirement is to assess the risk and to write and follow a scheme of control, and the scheme decides whether sampling is indicated: where the controls cannot be relied on, where the system has been out of use, where susceptible people are present, after remedial work, and routinely on cooling towers and similar equipment that aerosolises water by design. So the honest answer to a search for testing requirements is that your own scheme carries them, and if it does not say, the scheme is the gap.
How to prevent legionella in water systems, in order of effect
The measures are not equal and the order is worth knowing, because most systems fail on the first two rather than the last. Design comes first: remove dead legs and redundant pipework, size the storage to the actual use so the water turns over, and keep cold pipes away from heat. Temperature control second, which is the main control in almost every building: cold below twenty degrees, hot stored at sixty and reaching the taps at fifty or above. Turnover third: every outlet used, or flushed, at a frequency the assessment sets, which is what stops a guest room or a cleaner's sink becoming a reservoir. Then hygiene: showerheads and hoses cleaned and descaled, tanks lidded, screened and insulated, filters and strainers maintained. Then monitoring and records, because an uncontrolled system with a full logbook is common. Chemical treatment and point of use filtration come last and are for systems that cannot hold temperature, not a substitute for the four steps above.
Questions people ask about legionella monitoring
What is a written scheme of control?
The document that sets out the control measures for the water system, who monitors them, how often, the acceptable ranges and what to do when a reading is out of range.
Who should be the responsible person for legionella?
Someone appointed by the duty-holder with the knowledge, authority and time to make the scheme happen. The duty-holder remains responsible for the appointment being adequate.
How often is monitoring carried out?
The frequency comes from the scheme and the system. Monthly sentinel temperature checks are usual for hot and cold water systems, with tank and calorifier inspections less frequently.
What happens after a positive legionella sample?
The response should already be written into the scheme: review the control measures, disinfect or take other remedial action, resample to confirm, and consider whether anyone may have been exposed.
What does the L8 legionella code of practice expect?
HSE's L8 Approved Code of Practice expects a duty-holder who has identified a risk to prepare a written scheme of control, appoint somebody to manage it, and keep records showing it was followed.
What do legionella remedial works usually involve?
Removing dead legs and capped stubs left behind by refurbishments, insulating cold pipework away from heat sources, correcting calorifier and distribution temperatures, replacing materials that support growth, descaling and cleaning shower heads and hoses, and cleaning and chlorinating storage tanks. After significant work the system is disinfected and the records are updated, because the written scheme and the schematic have both just changed. On an older building this is where the money is, and it is unknown until the assessment has been done.