Sewage and drainage system in bathrooms can be designed in two ways:
Sunken system, which is what has been traditionally done in homes and is still being used in most builder floors/ villas which are under construction. In this all plumbing for sewage and drainage is buried below the floor of the bathroom in a sunken area created.
Under-slung system which is followed in hotels and now, mostly as group housing projects by all prominent big developers. In this system, plumbing for sewage and drainage is taken from below the slab.
Benefits of under-slung systems to the owner are:
If there is any leakage in sewage or drainage pipes in bathrooms, it becomes visible very soon, before the problem becomes too big.
Repair of any pipe is easy as no floor is to be damaged.
Family which is negatively impacted by the leakage, can get the work executed independently.