Landlords of rented accomodation are required to assess the risk of exposure to Legionella in the houses they rent. The guidance HSG 274 part 2, states that a simple risk assessment is required, but does not define the word 'simple'.
The risk in residential homes is generally low as the water systems installed are not complex and more importantly the house is lived in, which means the water system is used on a daily basis.
One of the main factors which cause the growth of Legionella bacteria is stagnation. This can be a big problem in businesses where areas of a building are not used frequently. In houses however, the showers, water heaters, taps and water tanks are all used on a daily basis, so the water never gets a chance to go stagnant.
A residential Legionella risk assessment is likely to highlight a few areas that need attention, for instance shower heads should be cleaned and descaled quarterly to stop the buildup of scale which can harbour bacteria.
One other thing that can cause problems in rented houses is the times when the property is empty, such as between tenants moving in and out. If a property is left empty for more than a week, stagnation can occur which can promote the gowth of bacteria. This can be combated by weekly flushing, but if the house is going to be left empty for an extended time, it may be necessary to drain the water system, including any water heaters and cold water storage tanks for the duration the property is empty.