Building services (sanitary work): For installing an Indian-type W.C. (squatting pan) on a reinforced concrete (R.C.C.) floor slab, what should be done to the slab level in the toilet portion to accommodate the pan, trap, and proper slope to the gully?

Introduction / Context:An Indian-type W.C. (squatting pan) requires room below the finished floor to place the pan, water-seal trap, and to provide a gentle gradient for the outlet pipe. Civil engineers commonly “sink” the slab in the toilet area for proper fitting and finished levels.

Given Data / Assumptions:

• Conventional Indian-type squatting pan with P- or S-trap.
• Nominal floor finishes and bedding mortar thickness.
• Need for adequate fall to the gully or branch sewer without raising the floor elsewhere.

Concept / Approach:

The sunk slab provides vertical space for the fixture and trap so the final toilet floor can be flush with adjacent rooms while still maintaining pipe gradients. A typical practice is a 20 cm sunk depth, which suits common pan depths and trap geometry without excessive excavation or step-downs.

Step-by-Step Solution:

Verification / Alternative check:

Check the finished floor level continuity with adjacent spaces and confirm the outlet pipe has the minimum gradient recommended (for example, 1 in 40 to 1 in 60, as per local practice and pipe size).

Why Other Options Are Wrong:

(b) Raising the slab complicates access and creates unwanted steps; (c) 50 cm is excessive and wasteful; (d) not sinking generally forces unsatisfactory pipe fall or raised platforms.

Common Pitfalls:

Insufficient sinking causing trap clashes; ignoring waterproofing, leading to leakage; not coordinating with tiling thickness and thresholds.

Final Answer:

Should be sunk by 20 cm