S-traps vs. P-traps: a Mitcham plumber explains different types of toilet configurations (2024)

Planning a minor bathroom renovation or considering some basic upgrades? Is your toilet looking a little bit old and not performing as it once did?

Before diving into the nitty-gritty of your bathroom upgrade, you need to make a choice: what type of toilet are you going to choose?

We’re not just talking about appearance, either – toilet configuration is something you should think of before starting your project.

Toilet configurations such as S-traps and P-traps stop foul gasses and water from flowing back into the bowl and your bathroom. They also serve as a filter for debris and other objects that might stop wastewater from flowing through your sewage pipes.

If you don’t have the foggiest about what type of trap your new toilet uses, don’t worry – by the end of this article, you will understand how plumbing traps work, and which type is best for your plumbing needs!

It’s a trap! The only question: what does it do?

Any plumbing fixture – tubs, sinks and toilets alike – features a trap.

A plumbing trap is a system of bending and curving pipes that block sewer gases from passing through drain pipes back to your home or building.

Sewage systems produce a whole range of foul gasses:

  • Methane
  • Hydrogen Sulphide
  • Nitrogen
  • Carbon Monoxide

Many smell terrible. Some are even lethal in high enough concentrations!

Plumbing traps protect your home from the risks that come with nasty sewage odours by ensuring that harmful gases (and waste – shudder!) don’t make their way back up.

Every time you flush, water goes down your toilet. Some of this water doesn’t go down to the sewer, instead getting trapped (hence the name) in the bend in the pipe.

This water creates a seal that prevents gas from passing back into your bathroom.

Fun fact: thanks to the bend in the trap, they also have a tendency to catch heavy objects that inadvertently fall in to the loo. That means things like watches and jewellery can often still be saved (though we’re not sure how comfortable you’d feel wearing them afterwards!)

S-traps and P-traps: what’s the difference?

When we talk traps, in our experience there are two types that appear in the vast majority of Melbourne homes (and toilets in particular): S-traps and P-traps.

What’s an S-trap, and how does it work?

The first is the S-trap.

Generally favoured for ground floor installations of floor mount-types of toilets (toilets where the pipe goes through the floor), this pipe got its name – how else? – thanks to its shape.

Resembling a sideways “S”, water from the bowl goes straight down and soars upwards before going down again, creating a trap at the bottom of the first bend.

As one of the oldest types of trap on the market, S-traps are extremely prevalent.

However, that also means that there are some sides to the design which are a little bit dated.

Firstly, S-traps take up more room around the waste outlet (which is why they’re more common for ground-level toilets).

A more pressing issue however is that they’re easier to siphon dry than other traps.

This can lead to the water level dropping, opening up gaps for sewer gasses to creep in. This can be remedied by pouring a glass of water in to re-establish a seal – regardless, it shouldn’t reach that point to begin with!

What about P-traps?

Imagine an S-trap, only instead of going down-up-down to create an S-shape, it goes down, curves up, then becomes straight, creating an open P-shape. That’s a P-trap!

More commonly installed in top floors and in wall-mounted toilets, P-traps are more commonly used in kitchen and laundry sinks.

P-traps are generally considered by most to be more effective and consistent in maintaining water trap compared to S-traps.

Their design makes them less vulnerable to drying out and losing seal: a properly installed P-trap will never lose its water seal.

When they’re not installed properly however, P-traps are just as prone to losing seal and allowing foul gasses into your home.

Make sure your toilet is installed properly by calling a fully licensed Mitcham plumber today!

Why does the trap my toilet uses matter?

Simply put, because you don’t have unlimited space!

Before committing to one type of trap over the other, you’ll need to ensure that the measurements work.

Both types of trap take up space, but in different ways – depending on your bathroom, you might only be able to support one type!

You’ll need to set out an imaginary blueprint of your bathroom and start measuring.

  • How much space do you have from the centre of the toilet bowl to the wall? This determines whether or not you can fit an S-trap.
  • How much space from the centre of the toilet bowl to the floor? This will determine whether you can get a P-trap to work.

No two bathrooms are identical, so you’ll want to go in with accurate measurements. If space is tight, you might even resort to a skew trap (where the drainage pipe is offset at 90 degrees and connected to an adjacent wall).

If you’re unsure whether you have enough space for a new toilet installation, don’t worry. Call H2-Pro’s Mitcham plumbers – we’ll know what to do!

S-traps vs. P-traps: a Mitcham plumber explains different types of toilet configurations (1)

Need a plumber in Mitcham? Call H2-Pro today!

Can’t decide between P-traps and S-traps on your toilet project? Contact Tony and the H2-Pro team today!

We’ve been in business since 2000 – that’s 18 years of repairing and installing toilets in homes all over north-east Melbourne. Trust us when we say we know a thing or two about choosing the most suitable toilet for your home!

Get immediate plumbing advice from Tony and the H2-Pro team today. Call (03) 9844 1444 or get in touch with us online for plumbing advice from a real professional… and a real local too!

S-traps vs. P-traps: a Mitcham plumber explains different types of toilet configurations (2024)

FAQs

S-traps vs. P-traps: a Mitcham plumber explains different types of toilet configurations? ›

Imagine an S-trap, only instead of going down-up-down to create an S-shape, it goes down, curves up, then becomes straight, creating an open P-shape. That's a P-trap! More commonly installed in top floors and in wall-mounted toilets, P-traps are more commonly used in kitchen and laundry sinks.

What is the difference between an S-trap and P-trap toilet? ›

Unlike an S-trap, a P-trap features a pipe that exits the toilet through the wall. Instead of creating an S shape by going first up and then down, a P-trap creates a P shape by going down, curving up and then proceeding straightly. Its specific form makes it ideal for wall-hung toilets.

What is the difference between a p-pan and a s-pan toilet? ›

An S-trap pan has a waste pipe that's connected to the floor. The P-trap pan pipe connects directly to the wall. The older style skew trap pan extends either side of the bowl.

Why are S-traps banned? ›

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 toilet pan? ›

January 14, 2022. S-trap toilet pans are a very traditional option and used where the waste outlet is located on the floor directly behind the pan. The 'S' refers to the shape of the porcelain waste outlet which comes up from the floor and finishes in the mouth of the toilet bowl.

What is the purpose of an S-trap? ›

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.

How do you tell what type of toilet you have? ›

Where can I find the model number of my toilet? Carefully remove your tank lid, and place it gently on the floor. You'll notice a four-digit number located on the back of the tank, near the water level mark. This is your tank model number.

Why do plumbers use P traps? ›

Your plumbing system, however, is a two-way street. A specialized fitting called a p-trap creates a powerful barrier that stops sewer gas and odor from entering your home. The trap is employed in any plumbing system that uses a drain and accepts sanitary waste from tubs, showers and sinks.

Can you replace an S-trap with a P-trap? ›

P-traps can be used for plumbing that exits through both the wall and the floor, making them usable for any plumbing fixture. There may be some difficulty in replacing your old S-trap to a P-trap so it would be advisable to seek professional help before taking on the replacement yourself.

What does an S-trap look like in plumbing? ›

An S-trap, like a P-trap, features an inverted curve, but it lacks the horizontal arm. Instead, it curves down, then up, then down again, like the letter "S," and connects to the drain pipe in the floor. What is P trap toilet? This is a P trap toilet.

What are the disadvantages of the S-trap? ›

One of the main cons of the S-trap toilet bowl is that the water in it is likely to evaporate if not used for a long time, especially during dry and hot weather. In addition to the foul smell, vermins such as rats and co*ckroaches from the sewerage system can come up from toilets through the dry strap.

Do you always need a P-trap? ›

Compliance with plumbing codes: P-traps are required where an open drain line discharges wastewater into a drain waste-vent system. Prevention of blockages: P-traps help trap solids that might otherwise clog the drain or sewer line.

Which trap is best for toilet? ›

The water in the P-trap prevents sewer gases from entering the room, as the gases are unable to flow back up through the trap. P-trap toilets are more common in modern construction and renovations, as they are more effective in preventing odors and are easier to maintain.

Do I need an S-trap or P-trap? ›

The water usage for each type of trap is generally similar. However, P-traps are often more effective at maintaining the water seal due to their design. S-traps, on the other hand, are more prone to siphoning, which can result in the water seal being compromised and allowing sewer gasses to enter your living space.

Does trap size matter in a toilet? ›

Sanitary Bar: Found on two-piece models, the sanitary bar blocks liquid from collecting under the tank at the back of the bowl. Trapway: The snakelike tubing on the sides of your toilet through which water flows. A larger trapway diameter (2-3/8 inches) reduces the chance of clogging and overflow.

Do you need a P-trap for a toilet? ›

Because of its bend, it always contains a bit of water to prevent dangerous sewer gas from seeping into your home. It's also something of a catchall for anything you accidentally drop down your sink drain. Toilets and bathtubs have P-traps, too. It is a necessary part of your home's plumbing system.

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