HC Deb 15 October 1990 vol 177 cc646-7W
Mr. Simon Hughes

To ask the Secretary of State for Health what advice he has received from the chief medical officer of the possible dangers to public health from the presence of viruses in water mains; and if he will make a statement.

Mr. Dorrell

Viruses are removed from mains water during the process of water treatment. These treatment processes are designed to ensure that the water supply meets microbiological standards and is not therefore a risk to public health.

Mr. Simon Hughes

To ask the Secretary of State for Health what assessment he has made of the possible dangers to public health from viruses in water mains and from leakage of harmful organisms and viruses from(a) water mains and (b) sewage pipes to (i) water services and (ii) land; and if he will make a statement.

Mr. Dorrell

As drinking water conveyed in water mains is treated to remove harmful organisms and viruses, leakages do not present a risk to public health. Potentially harmful organisms leaked from sewage pipes will be attenuated by natural decay and dilution, thus minimising the risk to public health. No land is free from naturally occurring bacteria or viruses and any additional risk from leaked sewage, unless in sufficient quantity to cause flood conditions, is minor.

Mr. Simon Hughes

To ask the Secretary of State for Health what assessment he has made of the possible damages to public health from(a) the flushing of water mains and (b) the reduction of water pressure in respect of any harmful organisms or viruses which may be present in water mains; and if he will make a statement.

Mr. Dorrell

As flushing is done with disinfected mains water which is flushed into sewers or surface water drains, there is no risk to public health. Following any significant drop in mains pressure due to some loss of integrity of a distribution system it is routine procedure for pipes into which contaminated water may have entered to be disinfected and flushed. The water is then sampled and analysed before it is returend to the public supply. Reductions in pressure for operational purposes are controlled to prevent contamination and minimise the risk to public health.