What are Traps in Plumbing?

A trap is a device that prevents sewer gases from entering the structure. The traps hold a small amount of water and are installed beneath or within a plumbing fixture. The holding water acts as a water seal, keeping foul gases from drain pipes from entering the structure. Therefore, traps are put in every plumbing appliance, including toilets, sinks, and washbasins.

Any device or fixture in the house that uses water can be drained using drain lines. It is linked to the main sewer system. As a result, the pipe should have a trap that can be used to seal the drain. A net is installed in the gully trap to keep debris out. The water seal’s height in the gully trap is between 60 and 70 mm.
The plumbing traps are of excellent quality. A bent pipe is used to create a water seal in any trap. In the plumbing fixtures in your home, you might have noticed floor traps, alley traps, p-traps, and other types of design traps.

Purpose of Plumbing Traps

Plumbing is made up of pipes that transport water to the building and sewage away. 

The sewer pipe transports the sewage to the disposal method. Sewer gases have a foul odour and may contain potentially flammable methane. 

Wastewater solids naturally break down due to bacterial activity, which results in the formation of sewer gases. 

The most common gases produced by the sewer system are nitrogen, carbon monoxide, methane, and hydrogen sulphide.

Traps are built at the ends of soil or waste pipes to prevent gases, insects, bacteria, cockroaches, and mice from entering the home or building. 

A trap should be installed on nearly all drainage pipes and fixtures in the home. Traps are necessary because they prevent sewer gases produced in drainage pipes from entering the house. 

As a result, traps are installed in all plumbing fixtures such as basins, bathtubs, kitchen sinks, and toilets, etc.

Plumbing Trap Specifications:

• The trap should be constructed from the right materials for adequate strengthening.
• To prevent gases from entering the house, the trap should be properly filled with water.
• To allow water to drain quickly, the trap should be free of grooves and have a flat surface.
• The inside of the trap should be smooth to allow water to escape quickly.
• If the trap is of good quality, the water should be able to clear itself.
• The trap’s connection to the drain should be simple.
• A simple and low-cost trap design is required.
• To keep debris out of the gully trap, a net is installed. The water seal stands between 60 and 70 mm tall in the gully trap.

Read more: Types of fitting in Plumbing | Types of Fixtures | Types of Pipes

Different Types of Plumbing Traps: 

Traps are commonly used in plumbing and come in a variety of shapes and sizes. These are as follows:

• Bell Trap
• Bottle Trap
• Building Trap
• Drum Trap
• Floor Trap or Nahni Trap
• Gully Trap
• Intercepting Trap
• Low-Level Bath Trap
• P Trap
• Q Trap
• Running Trap
• S Trap
• Straight-Through Trap

Bell Trap

The bell trap design makes it suitable for use in garages or outdoors. The water flows into a drain system well, which acts as a trap for foul air. A water seal inside the trap prevents sewer gas from entering.

Bottle Trap

A bottle trap is useful for collecting waste from the kitchen sink, wash basin, as well as some other sanitary items that lack a built-in trap. It consists of a vessel with a larger diameter than the plumbing pipe coming from the basin.

Building Trap

Building traps are pipes that connect a building’s drain to the sewer and have a U-shaped trap in the middle and an outdoor vent at the end. To maintain the water seal and maintain its cleanliness, a building trap must be vented. Although building traps can take on a variety of forms, they are typically a larger, more stable version of an S-trap to handle the increased demand. 

They are just as effective at repelling odours as they are at keeping unwanted bugs and vermin out of the house or structure. Building traps are used to avoid dangerous siphonage, which could result in the release of poisonous gases from the drain.

Drum Trap

The plumbing system in our home includes a device called a drum trap, which resembles a metal drum. Its large openings make it easier to locate and remove objects. Users must only retrieve or remove it from the plumbing system. 

Its wide caps also make it easy to insert into the trap. Clogs in the drain can be removed with a plumbing snake. It is frequently used in bathtubs. 

When water flows from the drainage to the plumbing trap, the bottom of the trap fills with water and always remains filled with a significant amount of water, preventing sewerage gases from entering our home.

Floor Trap or Nahni Trap

Floor traps are also known as Nahni traps. The Nahni Trap provides a water seal that prevents filthy vapours from entering the structure. A water seal of at least 50 mm depth should be provided. If wastewater flows, the floor trap stops foul gases (horrific odours) from entering the building. 

A floor trap, also known as a Nahni trap, is installed on the floor to collect wastewater from various locations such as the bathroom, wash zone, washbowl, and kitchen sinks. There are floor traps made of PVC, UPVC, and CI; they lack a vent pipe but have a detachable grinding that is visible at the top of the traps.

Some plumbing trap types used in the regions may lose their water seal due to dissipation. A plan should be devised to re-establish the seal by supplying water on a regular basis. By connecting the trap to a waste disposal system, it should be feasible.

Gully Trap

These traps are built outside the building to collect wastewater discharge from sinks, washbasins, and bathrooms. To prevent filthy sewer gases from entering the residence, they are connected to the nearest building drain/sewage. These are deep seal traps with a water seal depth of at least 50 mm. It also keeps cockroaches and other insects out of waste pipes that transport wastewater from the sewage line.

Intercepting Trap

Although intercepting traps are not required for homeowners, they are common in large buildings and intercepted sewer systems. They are effective and can handle large amounts of wastewater from various plumbing applications throughout a large structure. Most office buildings and large corporations require traps to meet their plumbing requirements while preventing sewage odours from escaping. 

Intercepting traps keep bugs and other pests at bay due to their depth and strength. Trap intercepting is more difficult than with other types of plumbing traps because of the duty they carry. Intercepting traps can be found in large buildings’ final main hole, where the sewer system enters the structure.

Low-Level Bath Trap

Low-level bath traps allow for overflow access, which is useful if there is a blockage. Low-level bath trap seals usually measure 38-40 millimetres and are quickly vented. Low-level bath traps may seem inconsequential, but they have robust seals that can keep out sewage odours. 

Due to their narrow design, low-level bath traps are perfect for use underneath bathtubs and showers. A low-level bath trap may not be suitable for all vent stacks, but it is well worth it.

P – Trap

This trap is appropriate for an Indian water closet. It is made of PVC or cast iron. It has a U-shaped tube that retains and prevents foul gases from entering. The P-traps are useful for a wall outlet.

Q Trap                             

These plumbing trap types are used in the submerged storage room of the latrine. It is similar to a S-trap and is used in the upper story rather than the ground floor.

Running Trap

These are typically found in public restrooms, where a single running trap is used to catch a variety of untrapped washbasins. It could be used in residential installations where a P or S trap setup is impractical. Although these appliances have specific traps, running traps are sometimes used with a washing machine waste output or dishwasher.

S Trap

This plumbing trap type is similar to a P-shaped trap and is used to fix water closets in latrines. The only difference between the P trap and the S trap is that the P trap is used for an outlet through the wall, whereas the S trap is used for an outlet through the floor.

Straight-Through Trap

This trap is ideal for small spaces and can be easily hidden behind the basin pedestal. However, the issue with this trap is that the water flow is slowed down by two tight bends. 
It contains a silicon membrane that acts as a non-return valve, allowing water to flow from its buds while preventing foul air from entering. 
This trap is ideal for pedestal basins and comes with various adapters, making it suitable for a variety of situations.