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 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.
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.
Remedial work, and 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.
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.