What Are Sink Traps? [Answers & Explanations]


A sink trap is a sort of plumbing device that is attached to the end of a fixture, commonly discharge and drainage systems; they are used to maintain and prevent the release of foul odor into the home or surroundings.

Sink traps are curvy in shape, usually having sharp bends at their edges.

A fixture, on the other hand, is an exchangeable device that delivers or drains water from your house. For example, showers, pipes, kitchen sinks, flush toilets, etc. are all part of your plumbing fixtures.

Sink traps are a fundamental part of such or all fixtures.

Traps are located in various parts of your home’s plumbing system. They are so important you have to have them attached to plumbing systems one way or the other.

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When wastewater is drained from your home into your sewage system, they stay there for a long time until nature acts.

septic tank-side view

At this stage, decomposition within the sewage system or septic tank starts to happen. When all these reactions begin, gases are released.

Make no mistake; these gases are choking and unbearable. In large amounts, especially hydrogen sulfide, they can burn the eyes and lead to instant death.

Because of these instances, traps are installed in every home. They prevent harmful gases from your sewers and even your drains from gaining access into your living area.

What a lifesaver!

How Does A Sink Trap Work?

Sink traps are attached to the tail ends of plumbing fixtures like your bathroom and toilet sinks, floor drains, and any various kinds of drainages.

To confirm, go to your toilet or kitchen. Look under your sink area or behind your toilet bowl. If you find any pipe that looks snaky or has paths that are bent and directly facing each other, you just found your kitchen/toilet trap.

So how does something as small as that rids your home of unwanted sewer gases? It’s simple.

If you live in a trailer, when you flush using your toilet or drain dishwater using your kitchen or RV sink, the water goes through your drain trap pipes into your sewage tank.

As you perform any of these activities, wastewater is collected by your drain pipes to your sewage chamber. When decomposition happens in the chamber, a lot of foul air is released.

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Because the pipe leading to the chamber is an open path, the foul air travels up the path. At this point, it enters the trap.

When this happens, the foul air is blocked by a wall of small water called a seal trap. The seal trap is between the inlet and outlet of your trap.

This is what prevents the pungent smell of sewer gases from filing your entire living area. As you continue to use your toilet or sinks, the water in the seal trap is continuously replaced.

Common Traps Used For Kitchen And Bathroom Sinks

Traps for sinks at homes, recreational vehicles, and industries come in varying shapes.

The most commonly used trap in kitchen and bathroom sinks is the P-trap. However, there are other alternatives that can be fitted to sinks used in kitchens and bathrooms. Examples are:

  • S-trap
  • Bottle Trap
  • Shallow Trap
  • Shallow Trap with inlet
  • Washing Machine S-trap
  • Magic waste trap

What Is a P-trap?

A P-trap is a kind of trap popularly used in kitchen and bathroom sinks at home that blocks sewage gases. P-traps come in two variants: Polymer Vinyl Chloride (PVC) and metal (made with chromium finish).

A P-trap is easily identified by the addition of a 90-degree fitting on the bend of the U-shape pipe, usually on the outlet side of the P-trap, forming a P.

The P-trap is located under your kitchen and bathroom sinks, and is sometimes hidden if the kitchen or bathroom sink is sitting on a countertop with shelves.

Parts of a P-trap

The P-trap has two openings. One collects wastewater from your sink, known as the inlet. The other, that sends the wastewater to your sewage pipes, is known as the outlet.

These outlets are connected by a U-bend which houses the seal trap. This chamber retains water when the P Trap drains water from your sink. It is usually called the seal.

The water or seal trapped at that U-bend prevents the foul smell from your sewer pipes from infiltrating into your home through your kitchen or bathroom.

How to Install a P-trap

Installing a P-trap is quite easy. However, before buying one and sticking it directly under your home or RV kitchen sinks or bathroom sinks, there are certain guidelines.

These guidelines should be followed strictly to prevent your P-trap from backing up.

  • Do not connect more than 3 sinks to a single P-trap. Never connect more than 3 sinks to a single P-trap. In addition, these sinks should not be too far apart from each other. Sinks should not be 30 inches apart each from the center of the drain that leads to the P-trap.
  • P-traps should be properly leveled to prevent backflow. The seal trap and the trap level in relation to the inlet and the crown on the outlet must be equal in height.
  • P-traps with larger outlets should never be connected to the ends of fixtures unless they are of the same width.
  • P-traps should be used more frequently. However, in cases where P-traps are seldomly used, a trap primer should be installed inside the P Traps. This is applicable in areas with high temperatures where evaporation is high. When the water in the seal trap is dried up, sewer gases will always travel back into your home.
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P-traps form an integral part of your plumbing system. Installing a P-trap to your kitchen sink is very easy. Below is an easy, step-by-step guide to installing one:

  • Connect the trap to the tailpiece that extends away from your sink drain.
  • Remove the trap arm from the P-trap and insert the trap arm in the drainpipe sticking out of the wall. Keep driving the arm until its entire length is inside the wall drain.
  • Take the trap arm and try to see if it fits without any adjustments into the lower part of the P-trap, which is the outlet. If the trap arm is a little too long, use a hacksaw to cut off the excesses. If the trap arm is too short, have it changed and get a longer trap arm.
  • If you get the alignments well, where the seal trap and the trap level are equal, insert the trap arm into the trap. Then, insert the slip nuts but don’t tighten yet.
  • Finally, once the parts joining the sink drain to the P-trap and the wall fitting have been carefully aligned, tighten the slip nuts.

And that’s it. You have just fitted a P-trap by yourself.

Benefits of P-traps in Sinks and Drains

It is okay if a P-trap eats up an ample amount of space underneath your sink area whether it is made from PVC or metal. This, perhaps, is the only downside here. Yet, it is as valuable to your house as having a roof on that same house.

Some of the benefits of the P-trap are:

  • For deep seal traps with vertical length reaching 4 inches, they trap enough seal, which is usually deeper. If installed in areas of high temperature, the water in the seal trap won’t evaporate quickly.
  • Deep seal traps can handle a large volume of water from drains.
  • P-traps help collect and trap debris at the bottom dip in the bend, and also prevent clogs. In turn, costs of maintenance and repairs are lessened.
  • P-trap saves you from property loss. Losing things through kitchen drains is common. It could be a special ring gifted to you by someone special, or anything of value small enough to pass the strainer in the sinks. Just know it won’t be going anywhere though, because it would be caught in the trap.
  • Sewer gases are extremely dangerous even in smaller amounts (e.g. hydrogen sulfide). However, they are easily trapped and prevented from infiltrating your living area by P-traps.
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Drain Odor: A Common Problem With Sink Traps And How To Fix It

There’s is nothing worse than having to sit inside a place that’s engulfed with bad odor.

Bad odor is one of the signs that there’s a problem with your drainage system. For this reason, it is important you give attention to it immediately.

Trap Failure

Traps in the sink prevent bad odor from sewers. The trap area is filled with a small amount of water that acts as a barrier.

When water is drained, the water normally should be replaced. However, there are instances where that may fail to occur, leading to drain odor.

When this happens over time, that particular sink trap should be replaced. On top of this, you can install an anti-trap siphon to prevent the drawing away of water especially if you live in a hot region.

Clogged Traps

Traps are clogged when debris and other scrapings occupy the body of the trap preventing proper water flow, thereby inducing wastewater odor.

To get this solved, unscrew the center of the trap and clean out every debris or clog material before fitting it back in place.

Poor Ventilation

Where ventilation is absent or just not enough, wastewater will drain slowly through your sink drain channels, or may not even drain at all.

This in turn leads to an outbreak of awful and noxious release of sewage gases. Solving this involves placing vents in a good spot that has plenty of air. This will improve the atmospheric pressure allowing wastewater to flow freely.

To End

Nobody loves getting invited into dirty and smelly homes. I know you don’t.

Therefore, it is important that your sink’s trap should be properly maintained and monitored to avoid the release of sewage gases in your home. They are as important as every plumbing equipment in your home.