Plumbing Trap

Plumbing trap is a part of the drainage system.

It is built or constructed to retain a little amount of waste water from the discharge.

In this article you’ll learn:

  • Purpose of plumbing trap.
  • Types of plumbing traps.
  • Merits and Demerits of plumbing trap.
  • Lots more.

So, if you’re ready to go with plumbing trap, this article is for you.

Let’s dive right in.

What is plumbing trap?

A trap is a depressed or twisted connection that is installed in a drainage network, which maintains a water seal by always remaining full of water.

It does not allow polluted air or gas to flow through it and it also does allow sewage or contaminated water to flow through.

 The trap is more effective the deeper the water seal, water seals range in depth from 25 mm to 75 mm.

Purpose of plumbing trap:

  • Traps are built at the end of soil or waste pipes to prevent air, insects, bacteria, cockroaches and rats from entering the habitat or structure.
  • They should be installed on almost all drainage lines and fixtures in the house.
  • Traps are necessary to prevent gutter gases from entering the house through the drainage line.

Types of plumbing trap:

According to shape:

P trap:

This trap is used in conjunction with the Indian toilet (ORISSA Pattern). Cast iron or Ultrasonic pulse velocity sheet are used to make the traps.

This trap also features a water seal, which prevents a part of noxious gases from entering the building.

Q trap:

In the toilet immersed storage chamber, these drainage trap designs are used.

 It’s almost like a S trap, and it is employed on the upper floors instead of the ground.

S trap:

This sort of plumbing trap resembles a P-shaped trap used to repair water closets in toilet facilities.

The only difference between P trap and the S trap is that the P trap is used for outlets that are accessible via the walls, while the S trap is used for outlets that are accessible through the flooring.

According to use:

Gully trap:

These plumbing traps are constructed outside the building to convey wastewater from the sink, washbasins, bathrooms, and other sources, and are connected to the nearest building drainage or sewers so that sewage fumes do not enter the home.

The depth of the water seal should be at least 50 mm.

It also keeps cockroaches and other insects out of drainage systems and trash pipes that transport wastewater.

The weight of the heavy cast iron gully traps should not be below 7.25 kg, and the frame weighing not be below 2.72 kg.

 The water seal should have a minimum depth of 50 mm.

Floor or nahni trap:

A floor trap is also called a nahni trap, collects drainage water from floorboards, kitchens, and bathrooms.

It’s made of cast iron that features a grating at the top to keep heavy items out.

This grating can be replaced to clean the trap on a regular basis.

Small water seals are used in these traps.

Intercepting trap:

This is a unique form of trap that is installed at the point where the house drainage enters the public sewer or septic system.

It is therefore installed in the last sump of the house drainage system and has a 100 mm water seal to prohibit bad odours from entering the public sewer line.

Bottles trap:

A bottle plumbing trap is provided to collect waste from washbasins, kitchen sinks, and other equipment that lack an underground trap.

Grease Traps:

These traps are only utilised in major hotels, cafes, and companies where substantial amounts of greasy waste are expected to enter the water supply.

A grease trap is a chamber made of masonry or cast iron with a twist pipe or T-pipe at the outflow end.

The velocity of flow is lowered as a result of the sudden increase in the area of flow at the entrance, resulting in the segregation of fatty and greasy debris from the wastewater.

These fatty substances that float on top can be removed early.

Drum traps:

Drum traps appear like metal drums are a significant aspect of a residential plumbing system because their big apertures make it easier to find and remove anything that needs to be retrieved or removed from the system.

Their broad caps also make it simple to slip a piping snake into the trap to clear blockages in your drain.

Water from a drainage pipe in your home enters the trap from the bottom and escapes at the top, leaving hard surfaces behind in the trap.

Because there is always water in the trap, sewer gases cannot flow into your home through it.

Running traps:

The running plumbing trap is specialized traps are available for these appliances, running traps are sometimes utilized with a washing machine waste output or cleansers.

Straight-through traps:

When there isn’t enough room for a trap, these are employed instead.

They’re also more concealable under pedestal basins.

The two tight curves in this design are the biggest drawback, as they slow the flow of water.

Low-Level Bath traps:

These are made to fit into tiny locations such as under bathrooms and shower trays.

 Because the seal on them is only 38 mm, they can’t be directly linked to the soil and vented stack.

Bell traps:

The Bell Trap Drain is designed to be used in the garage, on the balcony, or anywhere else outside.

The water is drained into the disposal unit’s pit, which serves as a sewage gas trap.

The filter attaches to the drain body with a clack 1 inch by two inches.

The Bell Trap Drain is designed to fit over 1 in.

Building traps:

Differential pressure and trap siphonage may make the sewer gas odour intolerable.

Health authorities are well aware that this may present a severe health danger, particularly in highly populated, moist, and dry places.

A peripheral line of protection against the scum and sewer gas was the building trap.

The building trap was usually a big diameter S-trap.

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Characteristics of traps:

The following criteria should be present in a plumbing trap as follows:

  • To perform the function, it must always have a suitable water seal.
  • It needs to be implemented with non-absorbent material.
  • It should be free of any internal projections, angles, or contractions that would hinder flow.
  • It should have a self-cleaning feature.
  • Appropriate cleaning access should be available.
  • Its internal and external surfaces should be smooth to prevent dirt and other contaminants from adhering to them.
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Advantages of the plumbing traps:

  1. Installation of the trap is easier and faster.
  2. The service life of traps is extended.
  3. It protects against the effects of the damage and the use of common household items.
  4. It also stops the foul gases, insects, and parasites from entering the drainage line.
  5. Traps are anti-rat and anti-self-cleaning.
  6. Most of the traps are conservative.
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Disadvantages of plumbing traps:

  1. The water in the trap quickly evaporates.
  2. The water in the trap easily evaporates.
  3. Methane gas explosion.
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Plumbing trap exist in a variety of shapes and sizes, they available in a wide range of materials including PVC, GI, and others.

Use the right and greatest kind of plumbing traps if you want your home free of unpleasant odours, bugs, and pests.

Hello, I'm Rahul Patil founder of, I had studied B.E. Civil. This blog provides authentic information regarding civil structures, equipment, materials, tests & much more.

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