What are S-Traps and Why are They No Longer Allowed? (2024)

What are S-Traps and Why are They No Longer Allowed? (1)All of the sinks in your home should have traps. In fact, your home has many other traps below toilets and other fixtures. Traps prevent sewer gases from getting up into your home so that it remains fresh and safe. Due to their design, traps may also collect clogs, but they’re conveniently close to the start of the drainpipe, so it’s simple to clean out those clogs. Plus, traps tend to catch lost jewelry or other small objects that are accidentally dropped down the drain.

While traps are essential, they aren’t all made the same. We’re advanced our trap design to make more consistent safer traps. In fact, a once quite common trap, an S-trap, is no longer allowed by most building codes. Yet, you may find one in your home, and it may be the cause of some of your plumbing issues. Here’s what you need to know about S-traps.

What are S-Traps?

S-traps look like the letter “S” on its side. It consists of two bends back-to-back, and it does not have a vent.This is critical because, without a vent, the S-trap eventually fails. You can still buy S-traps in stores, because they have some legitimate uses, but they aren’t suitable for beneath your sink. If you currently have an S-trap, it may have been installed before the building codes outlawed them.

What’s Wrong with S-Traps?

S-traps are known for siphoning water out of the trap. All traps are supposed to have water in the low point, which sewer gasses cannot pass through. However, when you run waterin an S-trap, the momentum of the stream may draw all of the water out of the trap. This breaks the seal and allows sewer gases to escape up into your bathroom.

This empty trap can be a health hazard. Leaking sewer gases may affect your health if inhaled and may create an explosion if they are flammable and exposed to a spark.Depending on the severity of the gas, they may not affect your health, but they will certainly make your bathroom smell.

For the short term, you can run the tap very slowly, and it may fill with enough water to seal off. However, the long-term solution is to have your plumber replace the trap and bring your home up to building code standards.

What’s an Alternative to an S-Trap?

There are many other types of traps that your plumber may use to replace your S-trap. For homes, the usual remedy is a P trap. It looks like a “P” on its side, with a deep drop that contains a lot more water than an S-trap could. It is vented, right at the bend and therefore avoids the siphoning problem. With the introduction of a bit of air, the water no longer siphons out to the drain.

Your plumber may need to make some larger changes to the bathroom in order to accommodate the new trap. As P-traps are vented, they need a vent stack, or to connect with one, to allow outside air down into the trap.

By Simpson Plumbing|2020-10-12T19:44:41+00:00October 8th, 2020|Uncategorized|

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What are S-Traps and Why are They No Longer Allowed? (2024)

FAQs

Why are S traps not allowed anymore? ›

The S-Trap's Major Flaw

The “s” design could cause a water siphon, removing the water built up in the curve, opening the seal, and allowing sewer gas to pass through. This flaw is whys-traps are no longer allowed in plumbing code and should be replaced if you have one.

What is an S trap used for? ›

What is an S-trap? S-traps are a type of plumbing trap that blocks sewer gases in sinks and other plumbing fixtures. The S-shaped pipe configuration traps wastewater before it drains to the sewer line, creating a water seal that prevents gases from flowing up through the drain.

When were S traps used? ›

History. An S-shaped trap is also known as an S-bend. It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880. The new U-bend could not jam, so, unlike the S-bend, it did not need an overflow.

Why are bottle traps illegal? ›

Bottle traps aren't code-compliant with modern building codes. Modern code doesn't allow for a pipe within the trap (also known as an internal partition), as if it cracks or fails, the homeowner won't be able to see it, and sewer gas may pass by.

What is considered an S-trap? ›

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.

What are prohibited traps? ›

The following types of traps are prohibited: Bell traps. Separate fixture traps with interior partitions, except those lavatory traps made of plastic, stainless steel or other corrosion-resistant material. "S" traps.

Why is it called S-trap? ›

They are named as such due to the shape of the bend in the pipe. For example, the S bend trap has the shape of an S, while the U bend has a U shape, and the P bend is shaped like a P. How the trap works is that it the bend fills with water.

Where are S traps found? ›

The most common places you'll find "S" traps are at plumbing fixtures that aren't vented, such as an illegal basem*nt bathroom sink, a DIY basem*nt bar sink, or a kitchen sink where the old steel drain in the wall was so corroded and blocked that someone installed a new drain, but never bothered to vent it.

Is S-trap or p-trap better? ›

The P-trap can prove to be a wise choice. The S-trap may let poisonous sewer gasses move into your home because of its design, something you certainly will not want. An S-trap may even let vermin move into your house if the trap remains dry for too long a duration.

What are three prohibited traps? ›

The following types of traps shall be prohibited: Traps that depend upon moving parts to maintain their seal. Bell traps. Crown vented traps.

Are S-traps legal in Texas? ›

The “S-Trap” is prohibited under the Uniform Plumbing Code throughout the United States. This is because an “S-Trap” does not maintain a water seal between the fixture and the trap and as such, “S-Trap” can siphon or suck water out from the trap as wastewater flows through the piping.

Are bottle traps OK? ›

Many building codes and regulations mandate the use of traps in plumbing systems. Installing bottle traps ensures compliance with these codes and helps avoid potential legal and regulatory issues.

Why are drum traps illegal? ›

Because of their design, drum traps are more challenging to clean than other types of traps, and their location can make it challenging to access the trap for cleaning. Another issue with drum traps is that they can corrode over time, leading to leaks and damage to the surrounding plumbing system.

Are bottle traps any good? ›

If you regularly clean out your bottle trap, it will prevent your sink from getting clogged. This is because the bottle trap's design contains the clog to a manageable area within the cannister. Without a bottle trap, any clogs would form deeper in the pipes which are not easily accessible or fixable.

Why are P-traps better than S-traps? ›

In addition to the different shape, a P-trap also has a vented pipe that rises from the fixture to and through the roof. This helps maintain air pressure in the drain, which in turn prevents gravity from pulling all the water through the pipe and leaving a dry pipe behind.

Is S-trap or P-trap better? ›

The P-trap can prove to be a wise choice. The S-trap may let poisonous sewer gasses move into your home because of its design, something you certainly will not want. An S-trap may even let vermin move into your house if the trap remains dry for too long a duration.

When did they stop using house traps? ›

House traps stopped being used around 1990. It was discovered that the problem they were meant to solve (sewer gases) could better be addressed by properly venting the house, having a P-trap in every drain line and also having sewer cleanout.

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