S Traps: A Thing Of The Past!

As a homeowner, keeping your plumbing system running efficiently is essential. But did you know that some older homes still contain outdated and potentially hazardous S traps? These relics of earlier plumbing systems need to be replaced with modern P traps to prevent clogs, leaks, and health hazards.

A Brief History of S Traps

The S trap was invented in 1775 by Alexander Cummings as one of the earliest types of plumbing traps. The distinctive S-shape was designed to prevent odors and sewer gases from entering buildings while allowing waste to drain. By the late 1800s, S traps were widely installed in homes and buildings throughout Europe and North America.

Despite being extremely common for over a century, flaws in the S trap’s design would eventually become apparent. But first, let’s understand what defines these outdated fixtures.

What Are S Traps?

S traps are U-shaped pipes or tubes installed under sinks, toilets, and other plumbing fixtures. The S-shape works to trap a small amount of water from the fixture, creating a barrier between the building’s air and the gases of the waste system.

The main components of an S trap include:

Inlet arm – Connects to the fixture’s drain pipe
Outlet arm – Connects to the main waste plumbing
Crown – The U-shaped bend

While S traps were effective at blocking gases when first installed, issues emerge over time:

Clogs – Debris gets caught in the tight S-shaped bend
Leaks – Joints and seals deteriorate, allowing gases to escape
Sewer gas accumulation – Gases bypass the worn trap and build up
Venting issues – The S-shape can cause airlocks and water to siphon out of the trap.

Despite these drawbacks, S traps can still be found in older homes and buildings, mainly constructed before the 1950s. However, they are no longer installed in new construction.

Why S Traps Were Outlawed

By the early 20th century, significant flaws with the S trap’s design and performance became undeniable. The most concerning issues included:

Frequent clogs – The narrow, horizontal segments of the “S” were prone to obstruction.
Sewer gas leaks – Deterioration and cracks allowed gases to leak into homes.
Health hazards – Exposure to sewer gases like methane, carbon monoxide, and hydrogen sulfide led to illnesses.
Plumbing code violations – Outdated S traps contradicted new requirements for anti-siphon prevention.

By the 1950s, nearly all plumbing codes in the U.S. and Canada banned the installation of S traps. Many municipalities also launched initiatives to identify and replace existing S traps in older construction.

Modern Alternatives – P Traps

Today’s plumbing codes require the use of P traps, which offer major improvements:

Benefits of P traps:

Hold water in their vertical leg to reliably block gases
Seldom experience clogs due to free-flowing design
Can be installed quickly and correctly by plumbers
Conform to all modern plumbing codes and regulations

Proper installation and maintenance are still required, as P traps can occasionally leak gases or dry out. Overall though, they provide superior performance and safety compared to obsolete S traps.

Identifying and Replacing S Traps

Homeowners wondering if they have an S trap can check for the following signs:

Frequent sewer gas odors in the home
Slow draining fixtures
Leaky pipe joints
U-shaped trap configuration

If an S trap is identified, a professional plumber should be hired to remove and replace it. DIY removal is not recommended, as it requires safely disconnecting drain lines. The plumber will:

Disconnect the inlet and outlet arms from the pipes
Remove the S trap completely
Install new P trap with proper slope and positioning
Attach water supply and fixture drain lines
Test for leaks

Replacement costs range from $100 to $250 depending on labor and material costs. This small upfront investment helps prevent far more costly damages down the road.