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020 4532 7773When a property sits empty, it is easy to assume there is nothing to worry about. No tenants, no complaints, no issues. But from a water hygiene perspective, a vacant property can actually present more risk than one that is occupied, particularly over the winter months when water temperatures fluctuate and systems go unused for extended periods.
Legionella bacteria thrive in stagnant water. When taps, showers and outlets are not being used regularly, water sits still in the pipework. If the temperature of that standing water falls into the range of 20 to 45 degrees Celsius, the conditions become ideal for bacterial growth. In the colder months, this is a very real concern for any unoccupied residential or commercial property.
This article sets out what landlords and property managers need to understand about Legionella risk in vacant buildings, what the law requires, and what practical steps should be taken before the winter period takes hold.
Occupied properties naturally flush their water systems every day. Tenants use the taps, showers and toilets routinely, which keeps water moving and prevents the kind of stagnation that allows Legionella to develop. When a property becomes vacant, that natural daily flushing stops entirely.
Over time, water sitting in cold pipes, storage tanks and dead legs begins to stagnate. If the building's heating is left low or switched off, temperatures in parts of the system can drift into the danger zone. Add to that any build-up of scale, sediment or corrosion in older pipework, and you have a combination of factors that significantly increases the risk.
This is not a theoretical concern. Legionella is present in many water systems at low, manageable levels. The issue arises when the bacteria are allowed to multiply unchecked due to poor water temperatures, stagnation and inadequate maintenance.
Landlords in England and Wales have a legal duty to assess and manage Legionella risk under the Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health Regulations 2002. This applies to both commercial premises and domestic rental properties.
Under the Health and Safety Executive's Approved Code of Practice, known as ACOP L8, the duty holder is required to identify whether conditions exist that could give rise to a Legionella risk and take steps to manage those risks. A Legionella risk assessment is the standard way to fulfil this duty.
Where a property is vacant and stagnant water is present, a risk assessment is strongly recommended. If the assessment identifies any concerns, flushing, cleaning and chlorination of the pipework and cold water storage tanks would typically be required before the property is let again.
Failing to carry out the necessary assessments and remedial work is not only a legal risk. It is a risk to the health of anyone who subsequently uses the property.
Many older residential and commercial properties in London have cold water storage tanks, often located in loft spaces or plant rooms. These tanks are particularly vulnerable during periods of vacancy.
Without regular use, water in the tank can become stagnant. If the tank lid is not fitted correctly, debris and contamination can enter the system. In the winter months, loft temperatures can fluctuate considerably, moving in and out of the temperature range that supports Legionella growth.
A tank inspection during a vacancy period should check that the lid is tight fitting and in good condition, that there is no evidence of corrosion or sediment build-up, and that the water temperature and turnover is acceptable. Where any of these conditions are not met, a professional tank clean and disinfection is the appropriate course of action.
If you are concerned about the condition of a cold water storage tank in a vacant property, our water tank cleaning service covers residential and commercial properties across London.
If you have a property that is currently vacant or is likely to become vacant over the winter period, there are several practical steps worth taking before the colder weather arrives.
First, arrange a Legionella risk assessment if one has not been carried out recently or if the property has been empty for an extended period. The assessment will identify any specific risks in the system and set out what remedial work, if any, is required.
Second, carry out a full flush of the water system. Running all taps, showers and outlets for several minutes flushes out any standing water and replaces it with fresh water from the mains. This should be done before any period of extended vacancy and repeated periodically during the vacancy if the property remains empty for more than a week.
Third, consider the temperature settings for the property. Hot water should be stored at a minimum of 60 degrees Celsius and cold water should remain below 20 degrees wherever possible. Leaving the heating completely off in a vacant property over winter is not always advisable from a water safety perspective.
Fourth, arrange a professional inspection and, where necessary, a chlorination of the system. Where there is an existing cold water storage tank, a professional clean and disinfection may also be recommended.
If any of the following apply to your property, a Legionella risk assessment should be booked as a priority:
The property has been vacant for more than one month. The water system has not been flushed or inspected recently. There is a cold water storage tank on the premises. The property has a complex water system, dead legs or redundant pipework. The property is about to be re-let to new tenants.
At London Water Treatment, we provide same-day Legionella risk assessments across London for both residential and commercial properties. Our assessments are carried out in line with current ACOP L8 standards and BS8558 specifications, and all findings are documented clearly for your records.
If you need a Legionella risk assessment for a vacant property ahead of winter, or if you have concerns about the condition of a water storage tank, get in touch with our team today. Call us on 020 4532 7773 or visit our Legionella services page for full details of what we cover.
