Example of bad feng shui practices courtesy of Fotosearch.com
Chi (energy) escapes through open toilets and drains. Remember to keep the lid down to preserve Wealth & Opportunities energy. Does this sound like crappy advice? Thousands of years of Chinese feng shui practitioners disagree! Try it and get back to us with your results. 🙂
Feng Shui By Fishgirl 
How do most Feng Shui Chinese keep chi in when most of them have open hole toilets with no cover?
You are correct that most Chinese families in China have old fashioned open hole toilets. To my knowledge, feng shui disappeared from practice in mainland China after the cultural revolution and most Chinese practicing it are elsewhere (Hong Kong, Phillipines, Taiwan, USA, etc) where modern plumbing exists. The concept of sealing the chi hole is rooted in ancient Chinese feng shui practice. Wealthier Chinese in ancient times would have practiced good feng shui by putting their open hole commode in a closed door room/cabinet. Thanks for your comment!
I was about to ask the same question when I saw your response. It makes sense and thank you for explaining it.