Vacant property is particularly at risk where stagnant water is more likely to build up and prove fatal to future occupiers. It only takes four days for legionella bacteria to multiply to dangerous levels in stagnant water found in purpose built water systems, such as industrial water-cooling systems, dishwasher and washing machine pipes or any system where stagnant water could be present.
For organisations, landlords and building owners, there is a requirement to manage properties that are not in service or not fully occupied. The duty holder remains responsible for the building.
Duty holders are often unaware of their responsibilities in regards to empty and vacant properties and so exclude such properties from water hygiene risk assessments and monitoring programmes on the grounds that they are not in use and therefore do not present a risk to personnel.
However the following practices may lead to exposure to stagnant water that has the potential to contain pathogenic bacteria including legionella.
- Security services, engineers/surveyors, maintenance personnel – although the building is no longer in use - works personnel may be in attendance and use the water services on an infrequent basis.
- Property Viewings – buyers and sellers, potential tenants and agents may attend property for viewings and in the course of the viewing may operate water services.
- Partial occupancy – a larger building designed for a greater number of occupants but is operating at a reduced capacity in a limited area such as one floor in a multi-floor building. These water systems remain operational however turnover is a fraction of that required leading to stagnation and increased risk.
- Empty properties incorrectly re-activated – a void property is re-populated without first disinfecting and flushing the water services leading to exposure of personnel to the stagnant water.
With empty and vacant properties, the legionella risk assessment is different from that required for an occupied building as there is likely to be a lower water turnover (increased risk) but a lower exposure (decreased risk). Cold water tends to warm up to room temperature, increasing risk but as room temperatures will be lower this results in a decreased risk.
Normal routine inspections may be reduced (decreasing the frequency of exposure) but any works carried out could involve contact with water which has become stagnant (increasing the intensity of exposure). Buildings that are empty for a period longer than 28 days require the water services to be de-activated.
Controling the Risks
A control policy is required for communication and management as the building transitions from normal occupancy to partial occupancy or complete vacation of the premises. This involves a handover procedure to include any control measures required to make the water system safe and any required methods by which this will occur.
Full Vacation of property – Defining the timescale is important to determine wheter vacation occurs within 1 month or is there a gradual reduction in occupancy levels. If the former, then as the building is vacated the water system should be completely de-commissioned.
Partial or Reduced Occupancy - if there is a gradual reduction in occupancy that is likely to occur over a period exceeding 1 month, or where a building occupancy is reduced to a level of 75% or less on a permanent basis then a Legionella Risk Assessment should be carried out to determine the appropriate method of control. Additional provisioning would need to be made for any gradual reduction in water storage to meet the needs of remaining occupants whilst maintaining a 24 hour turnover. All de-commissioning of the water services must be carried out by a specialist contractor who should implement clear labelling, lockable valves and detailed instructions to reduce the risk of un-authorised use. The Legionella Risk Assessment should be reviewed in all instances.
Re-commissioning of empty or Partially Occupied Properties - There are many serious documented outbreaks which have occurred in situations where both poor communication and bad management have lead to empty properties being re-occupied prior to correct re-commissioning procedures.
Plant and Assets with multiple outlets, such as air conditioning units, pose an especially large risk given the large number of people that they service. It is essential for property owners and managers to check, disinfect and maintain vacant property and to re-commision plant and assets as per the ACoP L8 requirements to ensure the risk of legionella bacteria is mitigated, especially if buildings house vulnerable people such as the elderly and children.
Simple precautions that will protect against legionella include a complete disinfectant flush of the property's water system four days before re-occupancy to eradicate any potential legionella before new tenants move in and which is certified. Once the system is re-activated, a review of the water hygiene risk assessment should be carried out to take into account the current and future use of the building.
Properties vacant for a short time only require a weekly water system flush with a suitable disinfectant to kill legionella bacteria present in the water system. One simple water test will demonstrate the lack of legionella bacteria present.
Failure of property owners and managers to carry out the correct precautions and adhere to the Approved Code of Practice L8, can lead to fines, prosecution and even imprisonment under the Corporate Manslaughter Act 2007 if deaths occur. It is therefore essential, and a legal requirement, to demonstrate due diligence in relation to legionella control.