Around the world people use bank machines to access cash: but in the Kenyan capital's crowded slums, people now use similar machines to access an even more basic requirement -- clean water.

In a bid to boost access to clean water, four water dispensing machines have been installed in Nairobi slums that operate like cash machines -- with customers able to buy affordable water using smart cards.

It has cut costs dramatically, and is helping improve health, residents say.

"It's pure and good for cooking, and above all it is affordable," said Peter Ngui, who runs a small street restaurant.

"I used to get water from far away, but this water system is closer to my place of work."

Previously people living in Nairobi's cramped slums struggled to get clean water cheaply.

Without water pipes or plumbing in the tin-hut districts, residents resorted to buying water from sellers who dragged handcarts loaded with jerry cans or oil drums into the narrow streets.

That water was often dirty, sometimes taken illegally from broken pipes.

But the new machines, installed by the government-run Nairobi Water and Sewerage Company (NWSC), allow people to purchase water directly -- and far more cheaply -- than before.

For the government, the machines allow them to make a profit, as water was previously stolen from them, with people cracking pipes to siphon off water to sell. For the people of the slums, the clean water provided is cheaper than that sold before.

- Six times cheaper -

"The project is commercially viable," NWSC chief Philip Gichuki said. "Illegal water services are going to die off because residents are assured of good water quality."

The new machines have made water up to six times cheaper. Previously, people would buy 20 litres of water (5 US gallons) in a jerry can from a street seller for three shillings, often from unreliable sources.

That price -- the equivalent of 3 US pennies -- was difficult for many slum residents who are unemployed or who only occasionally find work for $2 a day.

Now the machines sell the same for just half a shilling -- and the water is treated and safe to drink.

"We will have more and more people accessing water in a more dignified manner," Gichuki said, standing beside one of the new machines, as long lines of women waited to fill cans full of water, heavy loads they must then carry back home.

"The people in the informal settlements will improve in terms of their health standards and they will also spend less money in terms of water services," he added.

Residents load money onto the water smart cards at a nearby kiosk or via payments sent on a mobile phone -- a common system of payment in Kenya, which pioneered the sending of cash via phones -- then tapping into the machine how many litres they want to buy.

"This water project has come at a very good time, because if I have 50 shillings, I'll deposit it onto my water-ATM card, and get water from this point for a whole month," said Francisca Mbenya, who lives in capital's vast Mathare slum.

- Lack of proper sewerage -

The machines are operated by local residents -- youth and women groups -- who earn 40 percent of the profits from the water sales as an incentive to ensure they are kept running and the system is not vandalised.

Previously, pipelines were damaged when some people tried to steal the water. Now with the new machines and water points, the governments hopes there will be less reason to damage the pipes.

Lack of efficient sewerage and toilets mean water sources in the slums are often polluted, with diarrhoea common, while over 80 people died in a recent outbreak of cholera across the country.

Kenya's slums earned a grim reputation for "flying toilets" -- when people defecate into plastic bags due to a lack of other facilities, which are then hurled somewhere else into the shanty town. Conditions are improving however.

"I used to get water close to my home, but the problem was the hygiene level -- right next to the water point was a sewer," said mother-of-three Mbenya, as she tested the new water system. "This water point is clean."

The United Nations say access to clean water is fundamental right, while the World Health Organization (WHO) guidelines say people need a minimum of 20 litres of water a day as a basic requirement.