S-Trap vs. P-Trap: Which Toilet Trap Is Best for Your Bathroom Plumbing?

When it comes to bathroom plumbing, one of the most important components to consider is the trap system used in your WC (water closet). A well-functioning toilet trap not only ensures efficient flushing but also prevents foul odors from entering your home.

Two common types of traps used in toilet installations are the S-trap and the P-trap. While both serve the essential purpose of blocking sewer gases, they differ in design, application, and compliance with modern plumbing codes. In this guide, we’ll compare the S-trap vs. P-trap, explain how each works, and help you decide which one is best for your bathroom renovation or new toilet installation.

What Is a Trap in Plumbing?
A plumbing trap is a U- or P-shaped pipe that holds a small amount of water. This water seal creates a barrier that prevents sewer gases from coming back up through the drain and into your home. Every toilet, sink, and shower has a trap to maintain a clean and odor-free environment.

In the case of toilets, the most commonly used trap systems are the S-trap and the P-trap, each designed for different toilet plumbing layouts.

What Is an S-Trap Toilet?

An S-trap gets its name from its distinctive shape, which resembles the letter "S." This type of WC trap is designed for toilets where the waste outlet is located on the floor.

Key Features of S-Trap Toilets:

• The pipe curves downward in an “S” shape, connecting the toilet to a floor drainage pipe.
• Commonly used in older homes or traditional toilet plumbing systems.
• Ideal for floor-mounted toilets with vertical drainage.

Pros of S-Traps: 

• Suitable for floor-based toilet outlet installations.
• Often easier to install in homes with existing floor drainage.

Cons of S-Traps:

• Higher risk of siphoning, which can break the water seal and let odors escape.
• Increasingly restricted by modern plumbing codes.
• Less efficient odor control compared to P-traps.

What Is a P-Trap Toilet?

 

A P-trap is shaped like the letter "P" and is designed for situations where the toilet waste outlet connects through the wall.

Key Features of P-Trap Toilets:

• The trap forms a “P” shape with a horizontal pipe connecting to a wall-mounted waste line.
• Common in modern bathroom designs and new toilet installations.
• Designed to reduce siphoning and improve air-tight sealing.

Pros of P-Traps:

• More effective at preventing sewer gas odors.
• Compliant with most modern building regulations.
• Easier to maintain due to horizontal outlet positioning.

Cons of P-Traps:

• Not suitable for floor outlet toilets.
• Requires more space behind the toilet for wall access.

Which Toilet Trap Should You Choose?
Selecting between an S-trap or P-trap toilet depends on a few key factors:

1. Your Existing Plumbing Layout
If your bathroom’s waste pipe exits through the floor, an S-trap toilet is likely your only option unless the plumbing is reconfigured.

If the waste outlet is in the wall, then a P-trap toilet is the better and more compliant choice.

2. Local Building Codes
Many building codes now discourage the use of S-traps due to the increased siphoning risk.

P-traps are widely accepted and even required in many jurisdictions. Be sure to check your local plumbing regulations or consult a licensed plumber.

3. Renovating or Building New
In older homes, especially where the existing toilets are connected via floor drains, S-traps may already be installed.

In new constructions or modern bathroom remodels, a P-trap toilet system is usually the recommended and compliant option.

Choosing the right trap system for your WC is essential for maintaining proper function and hygiene in your bathroom. While S-traps are still seen in some older installations, they are becoming outdated due to issues like siphoning and non-compliance with modern plumbing codes.

P-traps, on the other hand, offer better odor control, are more code-compliant, and are the preferred choice in modern toilet plumbing installations. Before deciding, always assess your bathroom’s drainage setup, confirm with a licensed plumber, and review your local plumbing codes to ensure you select the most efficient and regulation-approved option for your bathroom renovation or toilet upgrade.

We stock a wide range of quality S-trap and P-trap toilets to fit any layout.
Visit us on the Spintex road near Manet Junction or call 0244334947 for help selecting the right toilet for your project. Our experts are here to help from advice to installation.