Secondary drainage is mainly to prevent water from infiltrating into the subfloor, and the invisible floor drain at the bottom can drain water through the floor drain.

This special attention, especially when the bathroom sinks, why do you do this?

Fu Shuo, an engineer who listens to the family, many people only made the foundation waterproofing of wall and floor tiles. If there is only one drainage, everyone knows that the water in the bathroom enters the sewer through the floor drain, and some enter the bottom of the porcelain plate through the gap. If there is no secondary drainage, water will invade bubbles and cause mildew, which will seriously enter the downstairs, causing mildew on the other wall. Therefore, the secondary drainage of the bathroom is necessary and not very troublesome. It's good for your family and neighbors.