In geomantic omen, there are real water and virtual water. Real water represents a place where water is as real as rivers, lakes and seas, while virtual water is a place relative to water. At home, the toilet is empty of water. Although it doesn't always contain a lot of water, compared with other rooms, it is the land of water in the home. The relative principle of Feng Shui is that one inch high is a mountain and one inch low is water. Therefore, as a place with water at home, its floor is lower than other rooms.
Someone here must have asked, the bathroom is not really water, so it doesn't matter if it doesn't have to be lowered by an inch? Actually, it is not, because the bathroom is the main water in geomantic omen, so if it is higher than other floors, it will violate the taboo that water does not return to its place, leading to the disorder of the five elements in the home, which is very unfavorable to the health and career development of family members.