Neither is inherently better. Choose a P-trap toilet for a wall waste outlet or an S-trap toilet for a floor waste outlet. Before buying, confirm the existing outlet direction and check that the toilet’s specified set-out range matches your plumbing. These are core checks when choosing a compatible replacement toilet.
What is the difference?
The difference between S-trap and P-trap toilets is the direction in which the pan connects to the sanitary drainage system.
| Configuration | Waste outlet | Connection direction |
|---|---|---|
| P-trap | Wall | Horizontally through the wall |
| S-trap | Floor | Down through the floor |
The letters describe the waste path, not the toilet’s quality or flushing performance. The configurations are not automatically interchangeable.
How to choose the right configuration
Check the outlet direction: A visible connection entering the wall indicates a P-trap arrangement; a connection through the floor indicates an S-trap arrangement. If the connection is concealed, check reliable installation records or ask a plumber to inspect it. Do not disconnect the toilet yourself.
Confirm the set-out: Set-out is the waste connection’s position relative to the finished wall or floor. For an S-trap, drawings usually specify the distance from the finished wall to the centre of the floor outlet. For a P-trap, they usually specify the outlet centreline height above the finished floor.
Check the exact model’s specifications: Use the manufacturer’s technical drawing to verify its permitted set-out range and required pan connector. Connector adjustment is limited and varies between models, so a near match may not fit. Incorrect set-out or connector selection is a common cause of toilet installation faults.
Changing between floor and wall discharge can involve sanitary drainage, concealed services, waterproofing or structural penetrations. Do not cut or relocate the waste pipe yourself. Contact our licensed Sydney toilet replacement team to check the outlet, set-out and model before purchase and complete any regulated connection work.