✅ Updated March 2026
Legionella Risk Assessments for HMOs:
What Rent to Rent Operators Must Know
Legionella is a legal compliance requirement for all residential landlords including rent to rent operators. This guide covers exactly what you need to do, how often, and what happens if you do not comply.
What This Guide Covers
The Legal Requirement for Legionella Assessments
The Health and Safety at Work Act 1974 and COSHH Regulations 2002 require all landlords to assess and control the risk of legionella. For residential properties including HMOs and SA, the risk is generally lower than for commercial buildings, but the legal obligation remains. As the rent to rent operator acting as the landlord in the tenant relationship, this obligation falls on you.
What a Residential Legionella Risk Assessment Covers
For a typical HMO, the assessment covers: mapping all water sources (taps, showers, water heaters), assessing risk factors (water temperatures in the danger zone of 20-45 degrees, dead-leg pipework, cold water storage tanks, infrequently used outlets), control measures (hot water reaching 60 degrees at the cylinder, cold water below 20 degrees, regular flushing of infrequently used outlets), and a written record of findings and controls.
For most standard HMOs with a combi boiler (no storage tank), the risk is very low and a straightforward written assessment confirming low-risk findings is sufficient.
Practical Steps for Rent to Rent Operators
For properties with a combi boiler: the risk is very low. You can conduct the assessment yourself using HSE guidance. Document the water system type, confirm hot water is supplied directly and not stored, note risk factors checked, and confirm control measures. Keep the written assessment on file.
For properties with a hot water storage cylinder or cold water storage tank: a qualified legionella assessor (typically 80-150 pounds) is recommended. Assess annually as standard, or after any property that has been unoccupied for more than a month – flush all outlets thoroughly before re-occupation.
Frequently Asked Questions
Do I need a professional to carry out a legionella risk assessment?
For simple domestic properties without storage tanks, the HSE guidance allows a landlord to conduct this themselves if competent to do so. For more complex systems a qualified assessor is recommended. Many operators use a professional for all assessments to ensure documentation is robust.
Can legionella survive in a standard HMO?
Legionella thrives in water between 20-45 degrees that is allowed to stagnate. In a well-occupied HMO where hot water reaches 60 degrees and all outlets are regularly used, the risk is very low. Highest risk scenarios: prolonged void periods, cold water storage tanks, and infrequently used showers. For more detail, see how to minimise void periods.
What should I do when a property has been empty for several weeks?
Before tenants move back in, flush all cold and hot water outlets for at least 2 minutes to remove potentially stagnant water. Run showers and taps throughout the property. If there is a hot water cylinder, confirm it reaches 60 degrees. Document that you have done this.
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Property Accelerator covers every compliance requirement for rent to rent HMOs and SA properties.
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