Greg Allgood has had some difficult jobs in his career at Procter & Gamble Co.

First, he was tasked with convincing the world that Olestra, P&G's fake fat, was safe to eat at a time when such products carried a label from the U.S. Food and Drug Administration warning consumers of gastrointestinal disturbances. (The label since has been removed.) Later, he started flying to developing countries, trying to sell a water-purifying powder to the world's poorest people. And just after that product had failed commercially, he was in Sri Lanka, working to persuade people like Mohamed Irshad that the powder would transform the water in his contaminated well, covered with a muddy layer of dirt and debris, into something that was safe to drink.

Dr. Allgood's latest task is part of P&G's effort to help with tsunami relief. Like plenty of multinationals, the U.S. consumer-products maker rushed to offer aid to victims of the tsunami, shipping 28 million packets of the water purifier to affected parts of southern Asia. What is different is that the product P&G is airlifting was a corporate bust.

Called Pur, the water purifier was envisioned as a revolutionary way to clean the world's drinking water. P&G realized it needed to develop a product that not only purified water but removed the sediment and dirt that makes water look dirty. The company started using iron sulfate, a coagulant that works like a "dirt magnet" to make dirt fall to the bottom of a container, in addition to chlorine salt in its powder mix. It spent four years and $10 million for research and development before launching the product in late 2002. Chief Executive A.G. Lafley championed the project, as had his two predecessors in the job.

The company decided to explore three different business models for the water purifier: selling the the small, powder-filled packets commercially for about nine cents to 10 cents each; selling it to not-for-profit organizations for eight or nine cents; and selling it at cost, about 3 1/2 cents, to emergency-relief agencies.

P&G first distributed packets commercially in Guatemala and later expanded distribution to countries including Morocco, the Philippines and Pakistan. Simultaneously, P&G sold Pur to Unicef to use in the aftermath of the December 2003 earthquake in Bam, Iran. The International Rescue Committee placed a big order to use during the Iraq war. Some markets, though, proved too difficult to crack. In Iraq, for example, after several International Rescue Committee workers were kidnapped, the organization realized that gathering people around to do product demonstrations of Pur was a bad idea.

But last year, P&G abandoned plans to sell the product for a profit in developing countries and drastically cut back its water-purification ambitions. The small packets of chlorine salt and iron sulfate are relatively complicated to mix and relatively expensive as well, prohibitive factors for most of the world's poor. In November, Dr. Allgood, who runs P&G's safe-drinking-water project, was worrying about how he would unload the millions of packets of the product sitting in a factory in Manila.

Then, shortly after the Dec. 26 tsunami, his cellphone started ringing with calls from AmeriCares, Unicef and the International Federation of the Red Cross with orders for Pur. Initially, P&G sold the packets to aid organizations at cost, but later decided to donate them because of the enormity of the disaster.

Still, the water purifier isn't always an easy sell, even when it is free. One problem, P&G concedes, is that the product practically needs an instruction booklet. The powder, which kills bacterial diseases such as typhoid and cholera as well as various viruses, needs to be mixed with a specified amount of water and then allowed to sit for several minutes. The clean water then must be filtered through a cloth, to separate it from any debris, before it can be consumed.

"It isn't something you can just throw off the back of a truck," Dr. Allgood says.

That is part of the reason that when Dr. Allgood arrived in Sri Lanka last month, he had to do some basic marketing to make sure people understood how to use the water purifier. In Sri Lanka, the product was unknown and Dr. Allgood, who has a doctorate in toxicology and a master's degree in public health, spent long days driving from village to village giving demonstrations of how Pur works and distributing samples. In his car, he carried bright-blue buckets and a trunkful of Pur packets.

On one visit to a refugee camp in Galle, on Sri Lanka's southern coast, he brought his bucket to a well that had been under 1 1/2 meters of water after the initial waves subsided and was contaminated and covered by dirt and debris. After filling the bucket with water, he asked the people gathered around to cut open one of the packets with a pair of scissors he had brought from his daughter's school kit. He talked them through the process step-by-step, telling them to pour the powder into the water and mix it for five minutes. The crowd made comments as clumps of dirt appeared in the water, and eventually fell to the bottom of the bucket. The last steps were to pour the water through a cloth into another container and wait for 20 minutes.

Dr. Allgood, laughing enthusiastically, urged children and adults to drink the treated water. When they hesitated, he chugged the water and challenged them to do the same.

Mr. Irshad, who saw the demonstration, said he wanted to use the packets Dr. Allgood left for him. But after the tsunami washed away many of his belongings, he wasn't sure how he was going to mix it. Although Dr. Allgood had left some buckets at the nearby refugee camp, Mr. Irshad didn't have one.

Eric Mintz, chief of diarrheal diseases at the Centers for Disease Control and Prevention in the U.S., says that introducing a new product in disaster zones is difficult. Dr. Mintz has worked with P&G on Pur and helped distribute the CDC's own water-purifying powder, which he says is slightly less sophisticated than P&G's and doesn't remove debris.

At a disaster site, Dr. Mintz says, relief workers typically are working at top speed. They are concerned about safe drinking water but also are dealing with people who are injured and need vaccinations. "They'll often do what they've done before, and if they have experience digging a well for water, that's what they'll do," he says. "We've found that an emergency isn't the best time to introduce them to a new way of doing things."