Water Supply in your flats 

Times have changed since Basil Fawlty worried about the pigeons in the water tank in “Basil the Rat” in 1975. The following year the bacterium Legionella pneumophila was identified after a large outbreak at a convention of the American Legion. Since 1976, building managers have become aware that “Stick some ply over it” as a precaution against vermin and “Brush your teeth in it but don’t drink any” are inappropriate to the problem. Organic materials, including wooden lids, as well as some gaskets and pipe fittings, are not permitted as they promote bacterial growth. Tanks should be cleaned when sediment, scale and biofilm have built up. These items are covered by two sets of legislation: The Water Supply Regulations (an Act of Parliament) and L8, the HSE’s guidance on the prevention of Legionnaires’ Disease. A water hygiene risk assessment is the starting point, and will consider the hot and cold water system as a whole.

The surveyor will pay particular attention to stagnation, the presence of organic materials and the water temperatures. Linked tanks and outlet arrangements where there is poor flow cause concern, and the recommendation will be to re-plumb the pipework so that water moves through most of the tank or tanks. The design and settings of hot water cylinders are checked to ensure that temperatures throughout the vessel are high enough to kill Legionella. In some instances it will be necessary to fit a shunt pump to move hot water through the whole of the cylinder during a period of low demand. A recent requirement is that where vents from the hot water system are found to discharge into the water tank they should be diverted to a tundish, which eliminates the possibility of warming and contamination. The primary method of Legionella control is temperature, which at outlets should be low enough to keep Legionella dormant or high enough to destroy it. This is controlled by adjusting stored water temperatures and improving insulation.  It is usual now for the report to back up recommendations with photographic evidence of corrosion, poor insulation, ramshackle lids, and on rare occasions remains of unfortunate drowned creatures.