* Children should drink six to eight glasses of water every day - three to four of them while at school, says the World Health Organisation

* Up to 10 per cent of schools still have no drinking water available to pupils

* Consumers in the UK are said to have drunk more than two billion litres of bottled water last year, more than twice the amount drunk in 1998. It cost them almost pound;1.2billion

* Mineral waters are tested for less than 25 per cent of the substances for which tapwater must be tested

* Bottled water can be 1,500 times the price of tap water - and it uses more than1.5million tons of plasticevery year

Water is big business these days. When Coca-Cola tries to tap into the market, you know the well of financial opportunity runs deep. The company’s bottled water, Dasani, was a multi-million-pound marketing disaster in the UK, when it turned out to be little more than souped-up Sidcup tap water (shades of Del Boy’s bottled Peckham tap), dispatched to our shelves after a much-trumpeted “state-of-the-art” purification process. Unfortunately, it had more than twice the legal limit of bromate, a known carcinogen. The point is, Coca-Cola knows a market when it sees one, even if it took a spectacular nose-dive on this occasion.

Drinking water is fashionable. Images of supermodels knocking back Evian or David Beckham reaching for the water bottle after a beautiful game have ensured its desirability. Consumption of bottled water in the UK topped two billion litres for the first time last year, up 18 per cent on 2002 and more than twice the amount drunk in 1998. Figures from food and drink consultants Zenith International also show that sales reached almost pound;1.2billion.

Chilled bottled water is appearing in every image-conscious office. Six to eight glasses of the clear stuff a day has become the new mantra for every dedicated follower of health fashion warned of the dire consequences of dehydration - anything from headaches and poor concentration to cancer.

Adults are getting the message, but do our children drink enough? How much should they be drinking and where from? A few years ago, Trevor Brocklebank, a consultant paediatrician at St James’s University Hospital in Leeds, now retired, was shocked to find that 50 per cent of his young patients, many referred to him with acute and chronic renal problems, were drinking nothing while in school. He, along with many others since, campaigned for safe water to be made freely available in schools. Much is happening but there is still more to do.

Why all the fuss?

Consumer choice has meant few of us have been drinking much water at all for the past decade, preferring fizzy, sugary drinks, fruit juices, tea and coffee. For some children the consequences have been serious. Dr Brocklebank blamed chronic dehydration for the growing numbers of children referred to him with renal problems. Over the years, schools and places of work have become dry, parched places. We spend more time indoors in centrally heated, air-conditioned rooms lit by fluorescent tubes as we sit in front of computer screens; conditions that suck moisture from the atmosphere. Children in school once drank from water fountains, or had milk, but no more. The once-common fountains have become few and far between: clapped out, broken, vandalised or placed in the toilets, where few children care to hang around, as they tend to be smelly and the haunts of bullies. Up to 10 per cent of schools still have no drinking water available to pupils. Hence children have opted for sweetened drinks, which they bring into school or buy from vending machines.

Health workers such as school nurse Radha Sethi in Manchester or Mary Cooper, community dietician in Leeds, and concerned parents such as Nicki Brander, whose research into dehydration was taken up by the Enuresis Resource and Information Centre (Eric), began to sound alarm bells. Ms Sethi, who surveyed 198 Manchester schools in 2000, found that 62 per cent had no accessible taps. She was also seeing rising numbers of irritable and lethargic children, with bed-wetting, constipation, and bowel and urinary tract problems. Sugary drinks are also blamed for aiding the rising levels of childhood obesity. Water is calorie-free, flushes the system and keeps the brain alert. Its image is on the up.

Did people drink more water in the past?

No. During industrialisation in the 19th century, drinking water was a killer, and many people drank beer instead. Way back, the Romans had systems for cleaning water and separating water supply and sanitation ducts, but they took their good practice with them. During the Industrial Revolution, water pollution increased alongside growing populations in the cities. Water “undertakers”, the companies that supplied drinking conduits, took it from rivers full of sewage. Indeed the Thames was so dirty, smelly and full of rubbish that it was called Monster Soup and in 1858, known as the Year of the Great Stink, the Houses of Parliament had to be closed and tens of thousands died from cholera and typhoid. Brandy was prescribed as a cure for cholera, delivered from shops via a “hole in the wall” - a commonly surviving pub name.

Beer was considered a therapeutic alternative for children and adults alike, as the boiling process in brewing rendered it germ-free. It was a doctor called John Snow who was able to show the government of the day the link between cholera and contaminated water. While dealing with a cholera outbreak in 1854, he realised that most people who caught it had drunk from the same water pump in Broad Street in London’s Soho. Consequently, 150 years ago, the Drinking Fountain Association set up its first source of free, clean water by London’s St Sepulchre’s Church in Snow Hill, and within a short time 7,000 people were drinking from it daily. Within 11 years 140 fountains were in place.

In the recent past we probably did drink more water. For the first half of this century there were few alternatives and people ate more vegetables with a higher water content than fatty, processed foods.

How much should we really be drinking?

There is some dispute. The standard recommendation by groups such as the World Health Organisation is that children and adults should drink six to eight glasses a day - three to four while at school - and more if the weather is warm or during exercise. Some say this is obsessive, faddish even, and those six to eight glasses could include other fluids such as juices, milk, tea or coffee and that, although diuretic, drinks such as tea are still hydrating overall.

Martin Schweiger, a consultant in communicable diseases for Leeds North East Primary Care Trust, who has campaigned for accessible, safe drinking water in schools, prefers the commonsense approach. Children and adults, he says, should check their urine. If it’s dark yellow and smelly, they are not drinking enough. If it’s a pale straw colour and odourless, water consumption is about right. If it’s virtually colourless and frequent trips to the loo are required, they’re probably drinking a bit too much.

Bottled versus tap?

What a raging battle this one is. The fall of Coca-Cola’s Dasani left suppliers of tap water triumphant. The water companies are fiercely defensive of claims by the bottled water business, often subliminal, that tap water is a less healthy alternative. According to Water UK, the umbrella organisation for the water utilities, the suggestion that any bottled brand is healthier than tap water is misleading. Indeed, mineral waters are tested for less than one-quarter as many substances as tap water. Regulations on spring waters are even more relaxed. Levels of sodium in some bottled water are as much as seven times the limit allowed for tap water. In a test of 51 bottled waters, Chester’s public health laboratory found that only 22 were within the limits for bacterial content set for tap water.

But surely people plump for bottled because of taste? At blind tastings between bottled and tap, many cannot tell the difference. Moreover, bottled water can be 1,500 times the price of tap water and the containers use up an awful lot of plastic. According to the Worldwide Fund for Nature, more than 1.5million tons of plastic are used to bottle water every year; toxic chemicals can be released into the atmosphere during manufacture and disposal and transport contribute to greenhouse gas emissions.

What are the benefits of hydration?

Our brain is almost 80 per cent water; two-thirds of our body weight is water; a human embryo is 80 per cent water, so if we are fully hydrated we function better on every level: our energy and concentration levels are higher and our skin is more supple. Teachers in schools where children are encouraged to drink, and have regular access to drinking water, note that pupils can concentrate for longer, that there are fewer dips in energy (notably before lunch and in the afternoon), that they are less irritable and have fewer headaches. Alan Heath, a brain gym instructor in schools who runs the Learning Solutions company in Bradford, says: “It’s like oiling a car. The brain is largely water and water is essential to aid its processes.”

Small amounts of water throughout the day are best. If children drink too much too quickly, mental performance can dip as the body works to rebalance water and salt levels. John Flockton, headteacher of Newhall Park primary school in Bradford, was aware of water problems in his school when he became head in 1996. “It was a well-designed, newly built school, but the drinking fountains were in the toilets and children wouldn’t use them,” he says.

Mr Flockton embraced an initiative by Yorkshire Water to donate water coolers to schools, giving a constant supply of chilled mains water. His pupils helped to design the smart, sports-type bottles for Yorkshire Water’s “Cool Schools” campaign. “This is a poor area, so I approve of anything for children that is beneficial and free to them. The children now fill their water bottles three times a day and they are just a lot brighter,” he says. “They don’t complain of headaches, and parents say they are not wetting the bed any more.”

What are the effects of dehydration?

Believe it or not, bed-wetting is one. People who do not drink end up with reduced bladder capacity. If children become thirsty at school and try to make up by drinking lots when they get home, their bladders cannot cope and they wet their beds.

Studies have shown that children’s mental performance is significantly impaired, even if they are only 1-2 per cent dehydrated. In the long term there may be health problems such as constipation, chronic incontinence, kidney and urinary tract infection, kidney stones and some cancers such as colon and breast cancer. In some studies, a decreased cancer risk was specifically associated with water. Obesity can also be exacerbated by dehydration, as poor hydration may stimulate a desire for fatty foods.

Where should schools get their water from?

Many school staffrooms already have chilled bottled water available, but storing large, wide water bottles in the quantities required to guarantee a steady supply in an average-sized secondary is difficult. There is also a health and safety issue as someone would have to hump them about. A mains system therefore seems more sensible.

What are schools doing?

Increasing numbers of schools, helped by recent government and water company initiatives, are doing a great deal. In Yorkshire more than 240 primary schools have taken advantage of a pound;700,000 investment by Yorkshire Water to donate 450 water coolers. The company aims to install coolers in all of the county’s 1,600 primaries, prioritising areas of social deprivation. Schools have to pay pound;199 for the installation and two years’ servicing.

The company’s Cool Schools initiative comes with educational material and “Cool Fuel” sports bottles designed for durability, as well as S-Cool, a free rap performance from an artist who goes into schools to educate children about the importance of drinking water. In Wales, in a joint pound;225,000 project between the Welsh Assembly and Welsh Water, 400 schools in Communities First areas - the 100 most deprived electoral wards in Wales - are also being offered water coolers, including installation and initial servicing costs. Pembrokeshire council, ahead of the game, started installing coolers two years ago. Sally Francis, head of Mount Airey infant school, Haverford West, says bottles are filled twice a day from the coolers and placed in crates in the classrooms A pound;1.5 million initiative from Glasgow City Council called Refresh20, starting this month, will also supply water coolers and bottles to 400 primaries.

What should staff be doing?

Drink water themselves. Make sure the water supply or cooler is in an open place, in full view. Allow children to fill up as much as they need and to go to the loo when they require. If pupils are not asking to use the loo at some point in the day, they are probably dehydrated. When a drinking water supply is first introduced, children will probably need to go to the toilet frequently, but over time their bladder capacity should increase and they will need to go less.

Will they throw it about?

Generally, no. After the initial excitement, schools that install a drinking water supply and allow children to drink water when they need it, fill up water bottles accordingly and keep them on or by their desks, find that pupils appreciate being able to quench their thirst and tend not to be silly with it.

Main text: Elaine Williams

Main photograph: Photonica

Additional research: Sarah Jenkins Next week: Homophobia