Seasonal Risk: Why Summer and Low Occupancy Are When Legionella Thrives
The Quietest Months in Your Building May Create the Biggest Water Hygiene Risks
When a building empties, water use drops. It’s important to understand Legionella compliance requirements to ensure water systems remain safe during periods of low usage.
Schools close between terms. Offices operate with fewer staff. Hotel rooms remain unoccupied. Residential properties can sit vacant.
But the water system remains in place.
Reduced water use can lead to stagnation, creating conditions that allow Legionella bacteria to multiply.
It is also one of the most preventable water hygiene risks we encounter.
What Changes During Low Occupancy?
Reduced occupancy means reduced water flow.
Outlets normally used several times a day may go untouched for days or weeks. Water remains in pipework for longer and temperatures can move outside recommended control limits.
Without an effective flushing and monitoring programme, these changes can increase Legionella risk.
The Temperature Problem
Legionella bacteria can grow between 20°C and 45°C.
During warmer weather, cold water temperatures can rise above 20°C. Reduced demand can also affect hot water temperatures and circulation.
Regular temperature monitoring helps identify these problems.
If monitoring stops during periods of low occupancy, you lose the evidence needed to demonstrate that your water system remained under control.
An unrecorded temperature is not evidence of a safe temperature.
Which Buildings Face Greater Risk?
Any building with fluctuating or seasonal occupancy can face increased water hygiene risks.
Schools and universities: Buildings may experience weeks of low or zero occupancy before students and staff return.
Hotels and leisure facilities: Rooms, showers and other outlets may remain unused for extended periods.
Offices: Reduced staffing can leave individual outlets, floors or entire sections of a building with little water use.
Residential buildings and HMOs: Individual rooms or properties may remain vacant during holiday periods or between tenancies.
Healthcare facilities: Wards or areas may temporarily close or operate at reduced capacity.
In each case, changes in building use can affect the effectiveness of existing Legionella controls.
What Should You Have in Place?
Low occupancy does not remove your existing Legionella compliance responsibilities.
Your control measures need to reflect how the building is actually being used.
Maintain Flushing Regimes
Identify outlets that are not receiving regular use and implement an appropriate flushing regime.
Complete scheduled flushing consistently and keep accurate records.
Continue Temperature
Monitoring
Continue scheduled hot and cold water temperature checks during periods of reduced occupancy.
Investigate temperatures that fall outside your required control parameters and record any corrective actions.
Review Your Legionella Risk Assessment
Changes in occupancy, building use or the water system may affect your existing risk assessment.
Review whether your current assessment and control measures still reflect the building and how occupants use it.
Maintain Clear Responsibility
Make sure responsible persons and appropriate cover arrangements remain in place during holidays, staff absence and other periods of reduced operation.
Close Outstanding Actions
Do not allow identified water hygiene issues to remain unresolved simply because occupancy has fallen.
Address outstanding actions and verify that appropriate controls are in place.
Don’t Overlook the Reopening Period
The return to normal occupancy deserves particular attention.
Outlets may have experienced reduced use for several weeks or months. Before normal occupancy resumes, review the condition and operation of the water system.
This may include:
- Checking monitoring and flushing records.
- Verifying hot and cold water temperatures.
- Identifying outlets or areas that have experienced little or no use.
- Completing additional flushing where required.
- Reviewing outstanding remedial actions.
- Considering whether further investigation, sampling or disinfection is required based on the system and identified risks.
This becomes particularly important in buildings occupied by people who may have increased susceptibility to Legionella infection.
Could You Demonstrate Compliance?
Consider what your records would show if someone reviewed your Legionella compliance today.
Could you demonstrate that monitoring continued?
Could you show that little-used outlets were identified and managed?
Are your temperature records complete?
Have you addressed outstanding actions?
Does your Legionella risk assessment still reflect the building’s current use?
If you cannot answer those questions confidently, you may have gaps in your current water hygiene controls.
Review Your Legionella Compliance
Changes in occupancy can expose weaknesses in water hygiene management that remain unnoticed during normal building use.
Irrigonics supports duty holders across schools, offices, healthcare settings, residential buildings and commercial properties with Legionella risk assessments, water monitoring and structured compliance programmes.
Request a Legionella Risk Assessment to identify potential gaps in your current compliance arrangements and establish whether your existing control measures remain suitable.
📞 Call: 0333 038 6286
✉ Email: Admin@irrigonics.co.uk