Once you have received your legionella risk assessment and have completed your remedial works to remove or reduce the identified risks, you won’t typically have to undertake the same works again. For example, installation of isolation valves, insulation, signage, etc.
You may however need to undertake further remedial action for ongoing tasks that may continue to change as time passes. For example, cold water storage tanks develop sediment, fill with scale, and debris over time. Temperature adjustments may be required over time. Thermostatic Mixing Valves (TMV’s) will require ongoing maintenance to ensure they remain within the compliant temperature range. And to ensure the filters are cleaned.
So whilst you won’t need to update or change the design of the water system, you will often need to continue with maintenance and service works. Also, if you change your water system in anyway, the works undertaken must be completed to the HSG 274 guidelines.
It is also worth bearing in mind that signage may fall off or be taken off by service users or customers, insulation may fall or become inadequate, or assets such as water heaters may fail and need replacing overtime.
In conclusion, whilst the majority of your remedial works won’t need further action, and you shouldn’t see them reappear in your legionella risk assessment. It is foreseeable to see cold water storage tanks requiring cleans in your legionella risk assessment every few years. Risk ratings can go from low to high from a lack of control and management from simple corrections. Non-compliant temperatures or heavy stagnant water may lead to high risk ratings from low as an example.