Working for water supply is my expertise. And working for latrines is my interest. I love to share with friends about water supply before dinner, and share with friends about toilet construction after dinner. Good design of toilet plays an important role in the hygiene in the camps or health structures. Latrines and wastewater disposal point are one of the major sources of spreading the virus. In the outbreak of SARS in Hong Kong, the toilet flushing is suspected to have caused the widespread of disease. In the field, one of the most popularly latrine designs is the V.I.P. (Ventilated Improved Pit) latrine. Pipe is heated up by sun. Air rises up through the pipe. Air is drawn down into the pit, passes through the pipeline. This creates ventilation. Air assists bacteria will break down the organic matters in the pit. There is little smell because of the ventilation. A well designed V.I.P. latrine can last for 5 years or more. The power of nature is amazing. The design of toilet has to fit the local context. In my first mission in Afghanistan, I was asked to design a toilet in a hospital. I flipped through the guidelines, and designed a fancy toilet block with 10 flushing latrines. Later I discovered that the hygiene condition is terrible and the latrines were often broken. The reasons are: No people have flushing toilets at their home. They don’t know how to use them. And more importantly… they do not use tissue paper after using but rough stones to wipe their butt, which damage the pipelines. In many occasions, simple idea can work better than the fancy ones.