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S-Trap vs. P-Trap: The Drain Line Savior

Black pipes and a p-trap underneath a sink in a wooden cabinet

S-Trap vs. P-Trap

Have you ever wondered what’s keeping sewer smells from coming back up your drain? Everything is connected, so why doesn’t the odor just come right back up? The answer is simpler you think!

Due to a now-standard plumbing apparatus, the P-trap, water is all that is needed to seal off unwanted smells from your sewer. A similar attachment, the S-trap, has a similar function but has been out of commission due to it being less effective. Yet, some older homes likely still have an S-trap as part of their drain system.

Here are the details on p-traps and s-traps and how they fit in your plumbing system.

How They Work

P-traps and S-traps both work by using water to create a barrier in your drain pipe, just under your sink. The barrier creates a seal that prevents sewer gases from coming back up your drain.

The P-trap is now the standard since the S-trap was deemed ineffective and prohibited in new construction under the Universal Plumbing Code. The S-trap was found to be prone to siphoning and drying out, which leaves the apparatus ineffective.

The Difference

The difference between the two traps is simple: the shape. An S-trap flows down from the drain, curves up, then curves back down. The P-trap also flows down from the drain and curves, but the curve finishes on a horizontal pipe that takes the waste out.

Once the trap dries out, sewer gases can start flowing back into your home. The quick fix is to run some water to recreate the seal. If you have an S-trap installed and frequently smell sewer gases in your home, consult with our plumbing team about switching to a P-trap.

Plumbing Solutions for Your Home

For efficient plumbing service from a highly qualified team, Lloyds Plumbing is the right option. Contact our experts today at (805) 495-8766 for the absolute service you deserve.