I have lived both in Australia and in Taiwan. In both countries, bathroom floors had drains to avoid serious flooding in the case of overflows. The bathroom floor drain in Australia even dealt with the problem of blockage of the regular drains/sewers: the floor drain went straight out through the wall above the ceiling of the lower story and had an angled flap to prevent drafts but allowed the water to escape.
Why have I never encountered such in US bathrooms?
Perce