Differences Between S Trap and Straight Trap in Floor Drains and Shower Channels

Differences Between S Trap and Straight Trap in Floor Drains and Shower Channels

Floor drains and shower channels are not only designed for water drainage. Their primary function is to prevent sewer odors, harmful gases, and insects from entering living spaces. The key component that determines this performance is the trap structure inside the product.

In this article, the component commonly referred to as an “inner cup” in practice is discussed by its technical term: trap. There are two main types of traps used in floor drains and shower channels:

  • Straight Trap

  • S Trap

What Is a Straight Trap?

A straight trap has a simple internal structure where water flows directly and vertically into the drainage pipe. It provides limited odor prevention by temporarily holding water inside the trap.

Technical Characteristics:

  • Simple internal design

  • Low production cost

  • Weak water seal

Disadvantages:

  • Water inside the trap evaporates if the drain is not used for a long time

  • Once the water seal is lost, sewer odors return

  • Limited protection against gas and insect intrusion

Straight traps may work in heavily used areas but are prone to odor problems in the long term.

What Is an S Trap?

An S trap features an internal structure shaped like the letter “S”, forcing water to follow a curved path before entering the drainage line. This design creates a permanent water seal inside the trap.

Technical Characteristics:

  • Continuous water seal

  • Prevents sewer gas backflow

  • Blocks insects and pests

Advantages:

  • Slower evaporation of water

  • No odor issues even in rarely used areas

  • High hygiene level

The S trap operates based on the classic plumbing siphon principle and is one of the most reliable solutions for odor prevention.

Comparison: S Trap vs. Straight Trap

Feature Straight Trap S Trap
Water Seal Weak Continuous
Odor Prevention Low High
Gas Backflow Possible Prevented
Insect Entry Possible Prevented
Long Periods of Non-Use      Odor occurs     No odor       
Hygiene Level Medium High

Conclusion

When selecting a floor drain or shower channel, focusing only on the grate design or material quality is insufficient. The trap structure determines real performance.

  • Straight trap: low cost, high odor risk

  • S trap: durable, hygienic, odor-free solution

For projects where odor and hygiene are critical, S trap floor drains and shower channels are clearly the right choice.