The water we drink


Seasoned British travellers are well aware that 30 to 50 % of their visits to developing countries and popular holiday areas are estimated to result in traveller’s diarrhoea. Known as Montezumas revenge, delhybelly etc, the episodes usually last no more than 2 or 3 days but can extend to weeks or months of illness. People from the UK have a higher incidence of diarrhoea than those travelling from other industrial nations. Toxin – producing strains of E. coli are the most common cause, contaminated food and water pass them into the gut and diarrhoea is the body’s response to get rid of the invading organism. Adults in areas of poor sanitation and hygiene develop resistance to such organisms, having survived their effects in childhood. This resistance persists on moving to another developing country. A study of expatriates in Nepal found that the incidence of diarrhoea began to fall after 3 months residence. (1) The body reacts to unfamiliar bacteria as well as those causing infection. Traveller’s diarrhoea can have a long term effect on the bowel (2) and may account for 1 in 10 cases of IBS. (3) The pockets in the colon with DD are an ideal breeding ground for bacteria, can traveller’s diarrhoea cause diverticulitis?

 Strains of bacteria are not the only differences encountered in waters, mineral content and pollutants can also differ from what a person is used to. Can holidaymakers in the UK or people in their own homes be affected by the water supply? People with DD can be sensitive to different foods which have no effect on the healthy, can there be the same effect with water? We all need water and are recommended to drink 2 litres a day in addition to that used in food preparation, cooking etc. Should we consider what we drink as well as what we eat?


The Drinking Water Inspectorate regulates the public water supply in England and Wales. Their website (4) provides a lot of information and links to water companies supplying water to different areas of the country. They carry out tests at water sources, service reservoirs (containing ready-to-use treated water) and at taps. There are rigid standards for the content of minerals, chemical pollutants and micro-organisms. Sometimes markers are used which show likely sources of contamination. For example, the presence of E. coli and other coliform bacteria indicate faecal contamination from animal or human sources, nitrate levels can indicate contamination by farm fertilizer. Any abnormalities will be investigated. The systems used in treatment works removes contamination, clarifies and disinfects water so that it is safe to drink. Water will have different tastes and hardness in different parts of a region or country and chlorine levels can be increased if there is increased risk of bacterial contamination. In an individual area, water can be obtained from more than one source, eg. a major source such as the Lake District or Welsh Mountains, a local upland reservoir, boreholes, rivers and springs. Different sources can have different tastes but this does not reflect the chemical and biological safety of the supply. Bottled water has quality standards imposed by the Food Standards Agency (5). The different tastes of these waters are due to their different mineral contents.


The water which comes from the mains to the taps is of high and safe quality for drinking. However, that supply chain does need repairs and maintenance. Repair of burst pipes, flushing and relining mains sometimes gives black or brown water and silt. Major works can last for weeks. How do we know when it is safe to use after such contamination? A local press report described, with pictures, how disinfected divers vacuumed sludge from the bottom of a service reservoir, such an incident did not encourage confidence. There is reliance on the dilution factor to overcome possible effects of such interventions but this is not the case with phosphates which can be added to the water locally to reduce leaching of lead from old (pre 1970) piping when this is detected. It is a good idea to flush out a tap and household piping which has not been used for some time or even overnight. This will reduce the levels of lead and any leaching from other piping materials which may affect the taste of water and get rid of micro-organisms which can grow on washers and the insides of taps. The supply pipes between the water main and the taps on a property are not the responsibility of the water companies. Nor are they responsible for installed water filters and softeners or portable kitchen filters. These require meticulous maintenance according to manufacturer’s instructions or can themselves become a source of contamination of water by micro-organisms from the gunge that builds up in them.

In high-rise apartment blocks and large public buildings such as schools, office blocks, hospitals etc., the continuity of supply of water is ensured by using storage tanks. Water quality deteriorates on storage even when strict guide-lines are followed. People should only drink from a tap or source labelled “drinking water” in such buildings. In apartments only the kitchen may be supplied directly from the mains and not the bathroom. In tower blocks even the drinking water may come from a storage tank for gravity feed. Some older houses also have a tank in which drinking water is stored, this may have been untouched in the attic for years. The Drinking Water Inspectorate (4) recommends procedures to avoid contamination of these tanks including annual cleaning and disinfection, and that the water is sampled and tested for bacteria 2 to 4 times a year 


About 1% of the population of England and Wales have private sources of water. The owner of the source is responsible for repairs and maintenance and many private supplies are not treated in any ways to remove chemical and microbiological contamination. These supplies are checked by local councils. A private supply to a single dwelling is not even required to be monitored routinely. Like residents in developing countries regular consumers of such water are not affected by it but their visitors and guests are at risk of serious illness and should use boiled or bottled water for drinking. If up to 25 people use a private source of water then it must be tested only once every 5 years. Holiday cottages are tested annually and hotels, camp sites etc. twice yearly. The quality standards applied are basic and not the same as to public water supplies. The water can change between tests. More monitoring takes place when a private water supply is used for food production (5) (6) but the system can fail occasionally (7). Many imported food products may also have been processed using indigenous water. It is good practice to wash fruits, salads, vegetables etc which are eaten uncooked.

When diet does not account for bowel problems with DD or the origin of an infection is unclear then perhaps water should be considered. Does the timing of symptoms coincide with a change of water? There is emphasis on sensitivity to diet of people with DD but the water supply is assumed to be blameless or not even thought about as a potential source of trouble. There is no medical research to support this article, it is based on personal and anecdotal experiences. Once again we have a situation which is investigated and researched for IBS but DD is not considered even when the effects of an infection could be life-threatening. 


(1) Conner BA  Sequelae of traveller’s diarrhoea: focus on post infectious irritable bowel syndrome. Clin Infect Dis 2005, 4,1 Suppl 8, S577

(2) Neal KR, Barker L, Spiller RC  Prognosis in post-infective irritable bowel syndrome: a six year follow up  study.  Gut, 2002, 51, 401.

(3) Goodyer L   Travellers’ diarrhoea. Pharm J 2002, 268, p917

(4) The Drinking Water Inspectorate

(5) The Food Standards Agency

(6)  Information on private water supplies

(7)  Sagoo SK et al   Microbiological study of ready-to-eat salad vegetables from retail establishments uncovers a national outbreak of salmonellosis   J Food Prot. 2003, 66, p403

© M Griffiths 2006

Note This article was used in the 2006 autumn/winter issue of Incontact magazine

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