The pump installed in Haiti's largest slum of Cite Soleil spews out clear but unprocessed water -- residents must add chlorine themselves to ward off cholera.
The problem is such chemicals are expensive, so most of the estimated 300,000 inhabitants of this desperately poor shanty town on the northern rim of the capital take a deadly risk every time they need a drink.
"When I have money, I buy packets of (chlorine)," mother-of-six Fifi Saint-Luce told AFP next to the pump on Monday morning. "Sometimes I cannot (afford it), so you drink the water as it is."
The epidemic has killed some 1,350 people. The toll is rising steadily and in this neighborhood -- its streets filled with garbage and pools of polluted water -- over 200 cases are admitted each day to the area hospital.
Haitian authorities hand out pamphlets written in creole with crude drawings explaining how to protect yourself against the water-borne Vibrio cholerae bacterium.
The instructions highlight the main defenses: washing your hands, diluting each liter of water with a drop of chlorine, and keeping human waste in deeply-dug latrines.
This new emphasis on sanitation has boosted the income of soap-seller Fanis Joseph.
"I sell more since the cholera," she told AFP, carrying around bags of soap and chlorine on her head. The chlorine sachets, enough to purify five liters of water, are sold for five gourdes (more than 10 cents) each.
Eying the soap-seller was Daniel Rosemont, father of two-year-old Davidson.
Asked whether he will buy the potentially life-saving chemicals, Rosemont gestured at the empty pockets of his grubby jeans.
"I have no money," he said, as his son drank the unsafe water.
"I am very scared for him. Also, I can't buy soap," he said.
The line at the pump was tense, and arguments broke out in the rush for water. Voices rose as one woman shouted at a man in the queue. Suddenly, she threw a glass bottle that shattered. The man pulled out a knife before the pair were separated by members of the crowd.
Nearby at Saint Catherine's Hospital, which is run by the leading medical aid group Doctors Without Borders (MSF), people arrived constantly for treatment.
A United Nations truck was parked near the entrance, with soldiers on hand pointing their guns at residents in this infamously violent neighborhood.
Inside the dank facility, patients lay on wooden cots with holes cut in the center for human waste.
"Cholera arrived two-and-a-half weeks ago in Port-au-Prince. At the start the number of cases was doubling each day. Since last week it has stabilized," MSF's Isabelle Janson told AFP
"Cite Soleil is a hotbed for the cholera in Haiti," said Renato Souza, one of the nurses. "We need to treat victims very quickly," he said, adding that without proper care victims can die from the disease in less than 24 hours.