Why Low Occupancy
Why Low Occupancy
is a Huge Risk for Legionella Outbreaks
Many organisations assume that lower building occupancy means lower risk. Fewer people using a building often feels like a safer, easier period to manage. In reality, the opposite can be true when it comes to water hygiene.
Low occupancy creates one of the most common conditions for Legionella growth: stagnant water. When outlets are not used regularly, water remains in pipework, temperatures drift into risk ranges, disinfectant levels reduce, and biofilm can develop. If normal use then suddenly resumes, contaminated water can be released through taps, showers, and other outlets.
This is why schools during holidays, offices with hybrid working patterns, and seasonal accommodation can all face elevated Legionella risk if water systems are not actively managed.
Why Low Occupancy Creates Risk
Legionella bacteria grow best in water temperatures between 20°C and 45°C, particularly where water is stagnant and nutrients such as scale, sludge, or biofilm are present.
- Water movement reduces significantly
- Infrequently used outlets become stagnant
- Hot water temperatures may fall below control levels
- Cold water may warm above safe limits
- Biofilm can build up inside outlets and pipework
- Problems may go unnoticed for weeks or months
When occupancy increases again, these hidden issues can quickly become a real health risk.
School Holidays and Education Buildings
Schools, colleges, nurseries, and universities often experience long closure periods during summer holidays, half terms, and festive breaks. During these times, classrooms, sports facilities, kitchens, and washrooms may see very little or no water usage.
This creates ideal conditions for stagnation in taps, showers, and little-used pipework. Large school buildings with multiple wings or older plumbing layouts can be especially vulnerable.
When staff and pupils return, systems may suddenly move from near-zero usage to full demand. If water systems have not been managed during closure, this can release poor-quality water or increase Legionella risk.
A planned holiday shutdown and reopening programme is essential. This should include regular flushing of outlets during closure periods, temperature checks, inspection of tanks where applicable, and recommissioning before reopening.
Offices and Hybrid Working: Lessons from COVID
The COVID-19 pandemic highlighted the Legionella risks associated with empty or partially occupied buildings. Many offices were left unused for weeks or months, while others moved to hybrid working models where occupancy remains inconsistent.
Even today, many workplaces have floors, meeting rooms, or washrooms that are only occasionally used. Reduced occupancy means certain outlets may remain stagnant for extended periods without anyone noticing. The challenge is that buildings may appear “open” and operational while parts of the water system are effectively dormant.
Offices should review usage patterns rather than assuming normal operation. Identify little-used areas, implement targeted flushing schedules, carry out temperature monitoring, and reassess the Legionella risk assessment where occupancy patterns have changed.
Hotels, Holiday Parks, and Seasonal Accommodation
Hotels, holiday parks, student residences, and guest accommodation often experience seasonal peaks and troughs. Entire rooms, blocks, or buildings may sit unused during quieter periods.
This creates a significant risk, especially where showers, en-suite bathrooms, and hot water outlets remain idle for long periods. When occupancy rises suddenly during peak season, guests may be the first users of stagnant systems. Reputational damage in hospitality settings can be severe if water hygiene failures occur.
Unused rooms and blocks should be included in flushing regimes throughout quiet periods. Before reopening or high occupancy periods, systems should be recommissioned through flushing, temperature verification, inspections, and additional sampling where required.
Low Occupancy Does Not Mean Low Responsibility
Protect Your Building with SAS Water Ltd
Whether a building is full, half full, or nearly empty, legal responsibilities under ACOP L8, HSG274, and wider health and safety laws still apply. Duty holders remain responsible for ensuring water systems are safe regardless of occupancy levels.
Reduced use often increases the need for active management rather than reducing it.
If your premises experiences closures, hybrid working, seasonal shutdowns, or fluctuating occupancy, your water systems may face greater Legionella risk than you realise.
SAS Water Ltd provides Legionella risk assessments, flushing programmes, temperature monitoring, recommissioning support, and full compliance management tailored to your building.
Why Low Occupancy Creates Risk
Legionella bacteria grow best in water temperatures between 20°C and 45°C, particularly where water is stagnant and nutrients such as scale, sludge, or biofilm are present.
- Water movement reduces significantly
- Infrequently used outlets become stagnant
- Hot water temperatures may fall below control levels
- Cold water may warm above safe limits
- Biofilm can build up inside outlets and pipework
- Problems may go unnoticed for weeks or months
When occupancy increases again, these hidden issues can quickly become a real health risk.
School Holidays and Education Buildings
Schools, colleges, nurseries, and universities often experience long closure periods during summer holidays, half terms, and festive breaks. During these times, classrooms, sports facilities, kitchens, and washrooms may see very little or no water usage.
This creates ideal conditions for stagnation in taps, showers, and little-used pipework. Large school buildings with multiple wings or older plumbing layouts can be especially vulnerable.
When staff and pupils return, systems may suddenly move from near-zero usage to full demand. If water systems have not been managed during closure, this can release poor-quality water or increase Legionella risk.
A planned holiday shutdown and reopening programme is essential. This should include regular flushing of outlets during closure periods, temperature checks, inspection of tanks where applicable, and recommissioning before reopening.
Offices and Hybrid Working: Lessons from COVID
The COVID-19 pandemic highlighted the Legionella risks associated with empty or partially occupied buildings. Many offices were left unused for weeks or months, while others moved to hybrid working models where occupancy remains inconsistent.
Even today, many workplaces have floors, meeting rooms, or washrooms that are only occasionally used. Reduced occupancy means certain outlets may remain stagnant for extended periods without anyone noticing. The challenge is that buildings may appear “open” and operational while parts of the water system are effectively dormant.
Offices should review usage patterns rather than assuming normal operation. Identify little-used areas, implement targeted flushing schedules, carry out temperature monitoring, and reassess the Legionella risk assessment where occupancy patterns have changed.
Hotels, Holiday Parks, and Seasonal Accommodation
Hotels, holiday parks, student residences, and guest accommodation often experience seasonal peaks and troughs. Entire rooms, blocks, or buildings may sit unused during quieter periods.
This creates a significant risk, especially where showers, en-suite bathrooms, and hot water outlets remain idle for long periods. When occupancy rises suddenly during peak season, guests may be the first users of stagnant systems. Reputational damage in hospitality settings can be severe if water hygiene failures occur.
Unused rooms and blocks should be included in flushing regimes throughout quiet periods. Before reopening or high occupancy periods, systems should be recommissioned through flushing, temperature verification, inspections, and additional sampling where required.
Low Occupancy Does Not Mean Low Responsibility
Whether a building is full, half full, or nearly empty, legal responsibilities under ACOP L8, HSG274, and wider health and safety laws still apply. Duty holders remain responsible for ensuring water systems are safe regardless of occupancy levels.
Reduced use often increases the need for active management rather than reducing it.
Protect Your Building with SAS Water Ltd
If your premises experiences closures, hybrid working, seasonal shutdowns, or fluctuating occupancy, your water systems may face greater Legionella risk than you realise.
SAS Water Ltd provides Legionella risk assessments, flushing programmes, temperature monitoring, recommissioning support, and full compliance management tailored to your building.
