An S-trap WC has its outlet pointing down into a drain in the floor. A P-trap WC has its outlet pointing horizontally back into a drain in the wall. Both have the same water seal inside the pan; only the exit direction differs.
Which you need depends on how buildings in your market are plumbed, not on taste. A WC with the wrong outlet type needs awkward adaptors or will not fit at all.
How each one works
The trap is the curved channel inside the ceramic that holds water and blocks sewer gas. In an S-trap pan, the channel curves down and ends at the base of the WC, over a floor flange or pipe. In a P-trap pan, the channel ends at the back of the WC, at a height above the floor, and connects to a pipe in the wall.
Wall-hung WCs are always horizontal-outlet. Floor-standing WCs come in both versions, and many factories offer the same model as S-trap and P-trap.
What markets usually use
Practice varies by country and even by building age, so treat these as broad patterns to check locally:
- The US and Canada use floor-outlet WCs set over a floor flange, described by the rough-in distance from the wall.
- Much of continental Europe and the UK use horizontal outlets for new work, often with wall-hung pans, though floor outlets are found in older buildings.
- India, parts of the Middle East and many African and Asian markets use both, with floor outlets common in many buildings.
- Projects can differ from the retail market. A hotel or apartment developer will specify one outlet type for all units.
The distance matters as much as the direction
For S-trap WCs, the key number is the distance from the finished wall to the centre of the floor outlet. For P-trap WCs, it is the height of the outlet above the floor. Both must match local practice. Toilet rough-in sizes for the US and Europe covers the standard figures.
Some suppliers offer adjustable or offset connectors so one pan fits several distances. These help, but they add parts and can reduce flush performance if poorly made. Check them in a test, not just on a drawing.
How to decide
Ask two or three local plumbers and distributors what they install most, and look at the WCs your competitors sell. If you serve both new-build and renovation, you may need both versions of your best models.
Then put the outlet type and distance on the purchase order for every model, and check them at inspection. Mixed S-trap and P-trap cartons are a common and avoidable problem. More on this in sanitaryware importer complaints.
Next step
We can check which outlet versions a factory makes for each model and confirm them on the line before loading. Book a free sourcing review.