How to Select Between S-Trap and P-Trap Toilets? Working, Differences, and Applications.

In this blog post, you’ll read:A toilet trap is an essential plumbing component present in the drainage system of a toilet. The trap blocks sewer gases using a U-shaped or S-shaped bend in the drainpipe. They retain a small amount of water within the curve. You need to know here before selecting between s-trap and p-trap toilets. S-Trap consists of a curved pipe that goes downward, forms an S shape, and then connects to the drainage system. S-traps are less common today and do not apply in modern plumbing installations. S-traps have been replaced mainly because P-traps are more effective. They excel at preventing sewer gas from escaping and are less prone to siphonage issues.

Table of Contents

What is a Toilet Trap?

A toilet trap is an essential plumbing component present in the drainage system of a toilet. The trap blocks sewer gases using a U-shaped or S-shaped bend in the drainpipe. They retain a small amount of water within the curve. You need to know here before selecting between s-trap and p-trap toilets.

p trap and s trap toilet
p trap and s trap toilet

What are S-Trap Toilet Bowls?

S-Trap consists of a curved pipe that goes downward, forms an S shape, and then connects to the drainage system. S-traps are less common today and do not apply in modern plumbing installations. S-traps have been replaced mainly because P-traps are more effective. They excel at preventing sewer gas from escaping and are less prone to siphonage issues.

What are P-Trap Toilet Bowls?

p trap toilet bowls
p trap toilet bowls

A P-trap toilet has a P-shaped pipe that keeps water in the bottom. It results in a barrier that prevents sewer gases from entering the drain. In a bathroom, the P-trap is built into the toilet bowl itself. That part of the toilet curves down and connects to the sewer pipe or drainage system.

Working of S-Trap Toilets:

When you flush an S-trap toilet, the wastewater and waste inside the bowl flushes down the drain. The wastewater and waste exit the toilet bowl and flow into the drainpipe.

The unique feature of an S-trap toilet is its S-shaped bend in the drainpipe. An S-trap toilet has a curved, S-shaped section of the drainpipe. The S-trap dips below the floor level and then curves back up before connecting to the sewer or drainage system.

The S-trap contains water in its bottom curve. This water blocks sewer gases and odors from traveling back up through the drainpipe and into the toilet. The water in the S-trap acts as a barrier to keep these gases contained in the sewer or drainage system.

S-trap toilets also require a ventilation system to prevent siphonage of water from the S-trap. It maintains proper drainage and allows air into the pipes to prevent airlock. The vent system is essential for the effective functioning of the toilet.

Working of P-Trap Toilets:

Working of p trap and S trap toilets
Working of p trap and S trap toilets

When you flush a P-Trap toilet, the water and waste inside the bowl are pushed down the drainpipe. As the wastewater and waste travel down the drainpipe, they encounter the P-trap. It is usually built into the toilet or lies below it. This shape of the trap gives it the name “P-trap.” The P-trap contains water in its bottom curve. This water prevents sewer gases and odors from traveling back up through the drainpipe and into the toilet or the bathroom.

In addition to the P-trap, the toilet plumbing system has a ventilation system. Ventilation is essential to prevent the siphoning of water from the P-trap. Its absence could break the seal and let sewer gases enter the living space. The vent system allows air into the pipes, preventing airlock and enabling smooth wastewater flow.

p trap working diagram
p trap working diagram

Applications Of S-Trap and P-Trap Toilets: 

S-Trap.

  • S-trap toilets are common in older buildings constructed before modern plumbing standards. These toilets may still be used in such structures for historical reasons.
  • S-trap toilets are used in some areas or countries due to plumbing standards and practices variations. They are becoming rare in modern construction.
  • S-trap toilets still apply in portable toilet installations at construction sites or outdoor events.

P-Trap:

  • P-trap toilets are the more applicable type in residential bathrooms. They are well-suited for typical household use.
  • Many offices, restaurants, and hotels also use P-trap toilets in their restroom facilities. These toilets suit high-traffic areas and provide efficient, odor-free waste disposal.
  • P-trap toilets are often mandated in regions with current plumbing codes and regulations. They have superior performance and reduced risk of odor issues. They are the standard for most plumbing installations.

Pros and Cons of S-Trap Toilets:

Pros:

  • Space-Saving:

S-trap toilets need less space behind the toilet bowl than P-trap toilets. Aesthetic Considerations:

S-trap toilets can maintain aesthetics because of existing plumbing configurations.

Cons:

  • Siphonage Risk:

S-trap toilets are more prone to siphonage. It can break the water seal in the trap, allowing sewer gas entry. This can create odors and potential health hazards.

  • Less Common:

S-trap toilets are becoming less common in modern construction. Finding replacement parts or plumbers familiar with their installation makes it challenging.

  • Compliance Issues:

S-trap toilets may need to meet up-to-date standards to ensure proper drainage. It could lead to compliance issues during inspections.

p trap vs s trap
p trap vs. s trap

Pros and Cons of P-Trap Toilets:

Pros:

  • Effective Odor Control:

P-trap toilets are more effective at preventing sewer gases from entering the bathroom. The shape of the trap retains water and forms a seal.

  • Compliance with Modern Codes:

P-trap toilets comply with modern plumbing standards, making them suitable for most construction projects.

  • Availability:

P-trap toilets, replacement parts, and plumbing services are readily available. It makes maintenance and repairs more straightforward.

Cons:

  • Space Requirements:

P-trap toilets take more space behind the toilet bowl than S-trap toilets.

  • Less desirable Appearance:

Sometimes, the appearance of a P-trap toilet may not be desirable, as it can differ from the aesthetic of older plumbing fixtures.

General Differences Between S-Trap and P-Trap Toilets: 

Here is a comparison between S-Trap vs. P-Trap toilets.

PropertyS-Trap ToiletP-Trap Toilet
Trap ShapeS-shaped bend in the drainpipe.P-shaped curve in the drainpipe.
Space RequirementsThere needs to be more space behind the toilet bowl.It needs more room behind the toilet bowl.
Modern Plumbing CodesIt may only meet modern plumbing code standards in some regions.Generally, in compliance with current plumbing codes and standards.
Availability and CommonalityBecoming less common in modern construction.Widely available and used in contemporary construction.
S-Trap Vs. P-Trap

S-Trap vs P-Trap: Which One is Best?

P-trap toilets are generally considered the better option due to their superior odor control. They offer reduced siphonage risk, compliance with modern codes, and proven performance. S-Traps are ruling out of the industry due to certain limitations.

Conclusion:

By now, you can select between s-trap and p-trap toilets. In comparison between S-Trap and P-Trap, both have specific properties. P-Traps being more convenient and efficient are the choice of the majority. At the same time, S-Traps can be suitable in some conditions while inappropriate in others. Yet, the selection of traps depends upon their usage and buyer demand.

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