By Alex Kirby BBC News Online environment correspondent

A community at work in Lusaka

They are working for nothing to build and maintain new drains that will not spread disease.

The capital cost of the drains themselves is being paid by the UK Government.

The incidence of malaria, cholera and other water-borne diseases has already fallen significantly.

The experience of the people of Mandevu is one of the subjects of City Slickers, a film made by Television Trust for the Environment (TVE) in its Earth Report series and shown on BBC World.

Click here to watch the programme

It is one of the Hands On films, made by TVE and the Intermediate Technology Development Group as guides to how poor communities are working to improve their lives.

Danger drains

Mandevu is home to 20,000 people, and conditions there can be grim.

Bamboo houses are cheap

One long-established resident, Joyce Phiri, tells TVE: "My family normally has malaria because of the mosquitoes in this drain... the water is stagnant, which makes it a breeding ground for the mosquitoes.

"In the rainy season the drains overflow, flooding our house and spreading malaria and cholera."

Most people in Mandevu use pit latrines, which can leak into the water supply, especially at times of high rainfall.

Lusaka city council has the know how to remedy the problem, and the UK's Department for International Development (DfID) is providing the money, through its City Community Challenge Fund.

The people of Mandevu provide the third component, their labour. Their aim is to build and then care for nearly 1,500 metres of flood-resistant drainage.

All their own work

Not far away in Chazanga, the British fund is paying for a VIP, a ventilated improved pit latrine. It is in the marketplace and near a bus stop, and is designed not to leak into the water table.

Vacutug to the rescue

One local resident, Irene Nkanga Mulundika, says of the townspeople building the latrine: "They have a sense of responsibility and ownership, and therefore you find there's sustainability - whatever it is you've done there is maintained."

Another project featured in City Slickers is a motorised rickshaw, the Vacutug, designed to extract human waste from pit latrines and septic tanks in the Bangladeshi capital, Dhaka.

Better homes

This means the job no longer has to be done by traditional human "sweepers", whose health is put at risk by their work and who usually tip their loads into the nearest pond or ditch.

Other initiatives by city communities to improve their lives covered in the film include a scheme to help squatters in Ecuador's second city, Guayaquil, to acquire inexpensive bamboo houses.

A poor Thai community is establishing its claim to be allowed to stay on its land in Chiang Mai by repairing a historic ciity wall and caring for an old canal.

And residents of an inner-city district in Bristol, UK, are co-operating to build their own sustainable homes.