S trap and P trap – Bottle Trap Type to Choose

In this blog post, you’ll read:What if your toilet bowl has broken or stopped working properly, and you will replace it with a new one? Replacing it is easy; you only have to find and install the best brand. But here arises a question: What else is the important aspect that affects the overall quality of drain traps? Here, I will help you dive into detail about the two types of drain traps. The choice between the S-trap and P-trap is based on the following points.

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What if your toilet bowl has broken or stopped working properly, and you will replace it with a new one? Replacing it is easy; you only have to find and install the best brand. But here arises a question: What else is the important aspect that affects the overall quality of drain traps? Here, I will help you dive into detail about the two types of drain traps. The choice between the S-trap and P-trap is based on the following points.

  • Bathroom plumbing configuration.
  • The type of toilet.

S-Trap and P-Trap


Kitchen sinks, toilets, or bathtubs all have a common aspect of plumbing fixtures: traps. They play various essential roles, including creating a trap seal of water that prevents foul-smelling gases such as methane, Sulphur dioxide, ammonia, etc., from getting into the living space by drain pipes.

By definition, toilet traps are channels that connect the end of the toilet bowl and end up in the waste/ drain pipe. Replacement is required when the traps dry up as this can lead to a foul smell, vermin, and even debris accumulator, which stops the water flow through sewage pipes.

S trap is the oldest trap in the market and gets its name from its shape as it is curved on itself as an “S” and goes down without having any horizontal part. They are mainly used while installing toilets on the ground floor. P traps replaced outdated S types because of the new generation of modern houses.

Furthermore, S-type drying can cause quick access of undesired odor into rooms where P types form a P-shaped water trap refraining from the entrance of sewerage odor. They are installed in the walls. It first goes down, then curves and proceeds straight. P types are beneficial as they retain water much longer than the S types and restrain sewer-fouled smelled gases from entering your bathroom. P types are mostly installed on second floors and other top floors. Or connect the drain to the sewer system.

p trap and s trap diagram
P-trap and S-trap diagram

How P-trap works

The p-trap toilet has p shaped trap. The curved pipe design helps retain water and create a barrier between the drain pipe and the toilet bowl. This makes it impossible for the unpleasant odors to flow back into bathrooms. They are mainly used in the present era renovations and houses. Plus, importantly, they are easiest to maintain.

How S-trap work

S trap toilets do not have a horizontal part and are primarily used in plumbing systems. S-type toilets contain a straight pipe that connects the toilet bowl where the trap is a bend in the pipe ending up in the drain pipe. This bend provides flexibility and provides effective work. They were the first to come into the market, so they are part of older and past buildings where the plumbing system is not applied. They are effective regarding installation where drain pipe has various locations for the toilet placement.

p trap and s trap comparison
p trap and s trap comparison


P-traps and S-traps come in various sizes to fit different applications, especially in household plumbing. Your exact size will depend on the fixture and local plumbing codes. Here are the standard sizes for these traps:


  • 1 1/4 inches (32mm): Commonly used for bathroom sinks.
  • 1 1/2 inches (40mm): This is a standard size for kitchen sinks, tubs, and showers.
  • 2 inches (50mm): Used for toilets and some commercial applications.

Trap Arm Length:

  • This refers to the length of the horizontal piece extending from the curved trap portion to the wall. The length can vary, but the most common lengths are between 6 to 20 inches. Your length will depend on the distance between the drain and the wall pipe.

Depth (for S-traps):

  • The depth can vary based on the design. It usually references the distance from the top of the trap curve to the bottom. This is more of a concern for S-traps, as the design directly influences the trap’s water-sealing depth.

Wall Bend Length (for P-traps):

  • This is the vertical length that connects the trap to the wall. Again, the length you’ll need will depend on your specific installation.

Inlet and Outlet:

  • Inlets and outlets often come in two common sizes (1 1/4 and 1 1/2 inches) but can have different configurations. Some traps might have a threaded end for screw-on connections, while others might be designed for compression or solvent-weld connections.

When purchasing or replacing a trap, it’s crucial to:

  1. Measure the drain diameter to ensure you’re getting a trap of the correct size.
  2. Check the distance between the fixture’s drain outlet and the wall or floor drain inlet.
  3. Confirm whether you need additional components or specific connection types.

Remember that while these are standard sizes, variations exist, especially in older homes or custom plumbing setups. Always consult local plumbing codes and professionals when unsure about the correct size or type of trap to use for a particular application.

Raw Materials

S and P-traps are commonly made from brass, stainless steel, PVC (polyvinyl chloride), or PP (polypropylene) plastics.

Polyvinyl chloride (PVC):

When used in plumbing systems, PVC pipelines are made of white plastic. PVC pipes, commonly used in plumbing, can be molded to suit and attach to your home’s pipes. Typically, P-traps are constructed from PVC.

pvc p trap components
pvc p trap components

ABS (Acrylonitrile Butadiene Styrene):

  • Properties: ABS is a black plastic material known for its strength, toughness, and resistance to temperature fluctuations.
  • Usage: Another popular material for residential plumbing systems, especially in regions with significant temperature variations.

Cast Iron:

  • Properties: This is a heavy, durable material that has been in use for centuries. It’s resistant to high temperatures and can be quite robust.
  • Usage: Older homes and buildings often have cast iron traps, though they are less common in newer installations due to their weight and the ease of use of plastic alternatives.

Chrome-plated Brass or Copper:

  • Properties: These are essentially brass or copper traps that have undergone a chrome-plating process. This gives them a shiny silver finish.
  • Usage: Used in visible plumbing setups, like under a bathroom or kitchen sink, where aesthetics matter. The chrome finish is also somewhat more resistant to tarnishing than uncoated brass.
  • Brass is used to make p-traps and other plumbing pipes. Although less common than plastic p-traps, some residences may have brass pipes. Brass is durable, but other steels, like galvanized steel, are also preferable for plumbing applications. Among China’s best P-trap manufacturing companies, Hofen Sanitary is one of the leading P-trap manufacturing companies in China. Most of its p-trap is built with durable brass with excellent corrosion resistance.

PE (Polyethylene) & PP (Polypropylene):

  • Properties: Both are types of plastic materials known for their flexibility, resistance to many chemicals, and durability.
  • Usage: PE or PP might be chosen over PVC or ABS for their specific material properties in some regions or specific applications.

Galvanized Steel:

This conduit material is known for its corrosion resistance. It is a popular choice for p-traps due to its resistance, but it is more expensive than plastic material.

However, specific raw materials for “s and p” traps may vary depending on the manufacturer and any recent developments in the industry. It’s highly recommended to buy from reliable and best p-trap manufacturers and suppliers as they use high-quality raw materials to manufacture the p-traps.

Stainless Steel:

  • Properties: Stainless steel is an alloy made primarily of iron, carbon, and chromium. When exposed to oxygen, the chromium forms a passive oxide layer, which gives the material its corrosion resistance. Depending on the grade, it might also contain elements like nickel, molybdenum, or manganese. Stainless steel is known for its strength, durability, and resistance to rust and tarnish.
  • Usage: Stainless steel P-traps and S-traps are often used in commercial establishments, upscale residential areas, and areas where high corrosion resistance is needed. For instance, stainless steel traps might be preferred in labs or areas with high exposure to chemicals. They’re also used for visible plumbing setups where aesthetics are important, given their sleek and modern appearance.
    • Grades: The most common grades of stainless steel used in plumbing applications include 201,304 and 316. The 304 grade is the most versatile and widely used, known for its excellent forming and welding characteristics. The 316 grade, often called marine-grade stainless steel, has an added element – molybdenum – which offers even greater resistance to corrosion, especially from chlorides like salt.

Stainless steel’s resistance to high temperatures, staining, and corrosion makes it an excellent choice for traps. They are also more environmentally friendly as they last longer and can be recycled at the end of their service life. When selecting stainless steel traps, it’s essential to ensure that you’re getting a genuine stainless steel product and not a cheaper, plated imitation.

stainless steel P trap
stainless steel P trap

Spare Parts

The spare parts of a toilet trap are typically

  • Rubber gaskets or seals  
  • Ball float valve (for older models)
  • Flapper valve
  • Fill valve or inlet valve
  • Flush valve
  • Trip lever or push button assembly
  • Overflow tube
  • Bolts and nuts for securing the trap in place
spare parts of P trap
spare parts of the P trap

Installation of P-trap

Installation of P-type is easy and cost-effective. You only need to cut out a hole in the drain pipe and then attach it to the drain. You need an elbow, wrench, pipe tee, and compression nut to install a P trap.

S type is installed under the ground floor. PVC glue is required for installation. You only need to consult the plumber for installation, which could be problematic.

  • The Advantages of the P-trap

P trap toilet is efficient as it maintains the water trap with consistency. P traps act as a natural seal of water. Water may enter the overflow pipe but would be restrained from entering the toilet bowl. This is because the water seal at the trap bottom stops the sewerage gas from entering the trap.

  • Why P-type is better than S-type?

S traps are least efficient as they dry out, leading to gas flow. Further, they are difficult to clean. Plus, damage leads to the complete replacement of the S-trap, which is quite costly. Further bacteria accumulation leads to foul odor and other issues.

  • How to turn an S-trap into a P-trap?

The efficiency of S traps lowers over time as it dries up. A pipe trap has a large diameter, which helps hold water more effectively. If there is any foul smell, add a cup of banking soda with one cup of vinegar and submerge the drain. After 10-15 minutes, pour a gallon of water that should be boiling. This would help in drain unclogging and removing the foul smell.

An S-trap and a P-trap have the same save for horizontal arm-length pipe on outside flow where the vent is connected. Incorporation of a 4-inch pipe and attaching it to the vent can lead to the conversion of an S trap into a P trap.

  • Selection

The trap type selection depends on the local building codes, plumbing design, and particular fixing requirements.

p trap vs s trap
P-trap vs. S-trap

Concerns while purchasing

Ensure you select a trap that uses local plumbing codes and maintains fixtures properly. Traps are competitively easy to install, repair, or replace. Regular maintenance can stop clog formation and ensure the proper functioning of the trap.


S traps are traditional and more convenient, while P traps are commonly employed in innovative plumbing based on their performance. General information on installing and repairing S and P toilet traps is below. However, most importantly, specific details depend upon the model and P and S-trap manufacturer.


ShapeResembles the letter “S.”Resembles the letter “P.”
Size1 1/4 inches (32mm),1 1/2 inches (40mm),2 inches (50mm)1 1/4 inches (32mm),1 1/2 inches (40mm),2 inches (50mm)
DrainageUsed when the outlet downwardly ends up in the floor drainUsed when the outlet ends up in the wall drain horizontally
InstallationHighly suited for floor-mounted toiletsSuitable for wall-mounted toilets
MaintenanceSlightly difficult to provide maintenance because of its S-shapeEasy to get maintenance access
CloggingHighly susceptible to clog because of designLess prone to clog
Visual Appearance after InstallationInvisible after installationResembles the letter “P.”
Odor ProductionThe S-trap placement produces a foul odorP-trap installation emits no odor
S-trap and P-trap specs comparison


  • First, start by turning off the water supply.
  • Remove the previous toilet trap.
  • Place the new S type for the ground floor or the P trap for wall mounting into the back of the toilet bowl.
  • Assure that the trap and the bowl are correctly connected.
  • Use a wax ring, gasket, or any other appropriate sealing material to create a watertight seal.
  • Re-attach the bowl to the trap.
  • Reconnect the water supply.
  • Finally, check for any leakage.
P-trap 0072b
P-trap 0072b


  • For trap leaking, turn off the toilet water supply.
  • Check for damage, cracks, or damage in the trap that can be the possible reason for the leak.
  • You can use epoxy or any plumber’s putty for minor cracks for sealing.
  • Replacing severely damaged traps with a new one is compulsory.
  • Follow the installation mentioned above steps to install the new trap properly.


Suppose you are unconfident, unsure, or uncomfortable with repairing or installing a new one. In that case, it’s always better to seek assistance from a professional plumber to prevent potential damage or issues.


  • Are chemical cleaners effective in cleaning clogged traps?

It’s better to use a plunger rather than cleansers as they can damage it.

  • Can I replace the toilet trap on my own?

It’s better to ask a professional as it’s complex to handle issues.

  • How to figure out a fault in a toilet trap?

Bad smell, slow drainage, water leak.

  • What is a toilet trap?

It’s located at the base of the toilet bowl. It acts as a water seal to prevent odd smells.


You will have to choose from several toilet bowl goods available on the market if you intend to install a new toilet bowl since your old toilet bowl has started to exhibit problems, such as a toilet bowl leak. Deciding between a toilet bowl with an S-trap or a P-trap would be best. Moreover, buying the S or P-trap from the best accredited and best bottle trap manufacturer is essential. It is crucial to understand their differences above. Every home has a wide selection of toilet bowl brands and models to suit your demands if you want to purchase one. Remember that a skilled plumber should install the trap you choose regardless of the type.

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