DIY S-Trap Toilet Installation | Hero Plumbing (2023)

S-Trap replacement

Almost all toilets, with the exception of composting and top-flushing toilets, have an internal S or P-trap. If the toilet is floor-mounted, it has an S-trap, and if it is wall-mounted, it has a P-trap . Both types of traps are used to collect sewage.

Due to the fact that the plumbing code prohibits the use of a double trap, installing a second trap in the waste line of a standard toilet is not allowed and is also unnecessary. This is because the toilet already has a trap. Read on to learn more about S-trap toilets and how to install an S-trap toilet yourself!

Gravity Flush Toilet Waste System

The toilet trap is built into the bowl. This means that the contours of the trap are visible when looking at the toilet from the side. The trap rises from its lowest point, immediately beyond the waste entrance, to a height about half way up the bowl. If the toilet is placed on the floor, the trap has a shape similar to the letter "S" and bends towards the floor.

On the other hand, the trap for a wall-mounted toilet continues horizontally to the back of the toilet, forming an inverted letter "P." After the waste passes through the opening at the top of the trap, it will go straight into the waste line. If the toilet is installed on the floor, a fitting called a closet bend is often placed just below the floor.

This fixture is angled 90 degrees and is placed just below the floor. Its purpose is to funnel the waste into a vertical stack that goes down the drain. Garbage produced by a wall-mounted device is sent straight to the landfill.

A guide to installing an S-Trap toilet bowl

S-trap toilet bowls have been around for a long time and are often used in situations where the waste outlet is on the floor directly behind the pan. The letter "S" refers to the shape of the porcelain waste outlet that starts from the floor and ends at the mouth of the toilet bowl.

(Video) How to install S Trap WC Complete

This exit rises from the floor. In many cases, toilet designers choose to rise from the waste hole in the floor and hide it either behind a set of drains or behind a small false wall. This allows you to use attached waste pipes to bring the opening up and out of the wall so you can use back-to-wall and wall-mounted toilets.

However, many people prefer to keep the classic look of S-trap toilets, and in some cases, they may aim to maintain the original theme of the facilities, such as in old buildings and oversized existing school toilets. A major reason for this preference is that S-trap toilets are more accessible to clean than other types of toilets. Here's how to install an S-trap toilet bowl in your bathroom.

Removing the old toilet

It is necessary to remove the outdated toilet as soon as you have itshut off the water supply networkpowering and disconnecting it. While doing this, you need to pay close attention to the area where the toilet bowl meets the waste outlet on the floor. You should aim to ensure that the waste outlet is slightly disturbed by your work. Debris may be held in place with cement mortar in some cases. If this is the case, you should remove it very gently.

Finding the S trap under the toilet bowl

When you have finished cleaning and securing the waste outlet and installing a pan connection, you will need to install the toilet bowl. Adjust the alignment of the toilet bowl so that the vertical waste outlet can be connected to the floor via the bowl connector.

It should provide a seal that is impervious to water. After you have set up your toilet and made sure it is level, you will need to use the safety fasteners provided to screw or tighten the toilet bowl bolt to the floor.

Installation of the water supply network and the tank

After the pan is secured in place, the next step is to attach the cistern to the pan, paying particular attention to creating a tight seal. This is often done by inserting a rubber flap or seal into the connection. You can find this connection between the cistern and the pan.

(Video) How To Install A Toilet

Once this is ensured, you can turn the mains water supply back on. Once the water supply is back on, the toilet can be checked for leaks or water that has escaped.

Need for ventilation

Although building a trap into a toilet waste line is not necessary, a vent is required to be placed in the line. This is a pipe that extends upward to reach the home's main vent stack, which is installed in the roof. Ventilation is a necessary ingredient in successfultoilet operation.

Without it, waste won't be able to flow easily through the pipes, and the suction it causes can empty the water out of the toilet trap, exposing the bathroom to sewage gases. So if you don't have ventilation, you should get it. The architecture of the waste system determines the placement of the vent. This means that in some cases, it is embedded in the waste pile, rising up to the point where the waste goes down the drain.

In other cases, the vent is located elsewhere. The plumbing code defines the maximum distance this vent can be from the toilet trap. While this maximum distance can also vary depending on the layout and diameter of the pipe, it is usually between 6 (1.8 m) and 10 feet (3 m).

Sometimes it makes sense to use the vent pipe from the sink to vent the toilet, depending on how the plumbing is set up in the bathroom. Other times, no. This process is known as wet venting and is something that should be done by a licensed plumber who knows all the regulations that apply in your area.

Method of Hydraulic Wet Aeration Toilet

If you want to vent a toilet line into the sink drain, you can do so according to the International Plumbing Code (IPC) and the Uniform Plumbing Code (UPC). Unlike a dry exhaust, a wet exhaust needs a pipe diameter of at least 2 inches (5 cm) since it carries water and air.

(Video) Rimless toilet installation, back to wall

To vent a toilet line through a sink drain, a popular method is to connect the sink drain to the toilet waste line with a descending sanitary mesh with the sweep oriented in the direction of flow. Perpendicular to the drain pipe, the outlet of the T-shirt should be facing upwards.

In environments, such as basements, where gravity does not work well because the drains are above the toilet, a riser toilet is used. Waste from the toilet is collected in a tank located behind the toilet. It is here that it is then crushed and ejected by a pump through a water pipe that is either one or three-quarters of an inch (2.5 or 1.9 cm) in diameter.

Although pumps often come with their own internal traps, local plumbing codes may require that you install a P-trap (rather than an S-trap) in the discharge pipe in addition to the trap already in place. You should send this question to your local plumbing authority.

The three common ways to ventilate a toilet

Connects directly to the vent stack

It is sometimes beneficial to extend a vertical vent upward from the point at which the pipe leading from the toilet drain drops vertically into the drain. You do this by gluing the vent pipe to the upward facing port on the sanitary tee, which is used to make the waste connection.

The sweep of the sanitary t-shirt should be oriented towards the drain. It is also advisable to route the waste pipe into an existing soil stack and tie it to the stack using a wye fitting with the wye facing down. This method is commonly referred to as the "straight and tie" method.

Both of these tees are often used in drainage fittings. In contrast, the inlet of a wye fitting, which is shaped like the letter "Y", is long and straight. A healthy T-shirt, on the other hand, has a slight curve at the intake port. You can reduce the vent size to 2 inches (5 cm) by tacking on a taper ring, but if you live in a UPC jurisdiction, keeping the diameter the same is more beneficial.

(Video) How to install P Trap WC Complete

This is because the UPC (Uniform Plumbing Code) states that at least one of the vents in the home must be the same diameter as the sewer line. This would then become the main vent stack in the hydraulic system, to which all other vents would connect.

Bring it all together using a wye and a street elbow

A typical method for venting is to install a wye in the horizontal drain line with its sweep directed toward the drain and taping a 45-degree tee at the outlet of the wye to direct the vent vertically upward, usually to the wall behind the toilet or on another wall in the area.

This method is also known as the "wye and sweep" method. When transitioning from a 3- or 4-inch (7-10 cm) diameter drain line to a 2-inch (5 cm) diameter drain line, use a decreasing lump. Point the sweep of the wye fitting in the direction of the sewer.

Install the toilet vent adapter

You can install the vent in the standpipe before installation if the toilet waste pipe descends vertically in a long sweep elbow. This allows you to avoid cutting the pipe. To do this, you would use a reducer vane with its sweep facing down, then use elbows to adjust the direction of the vent pipe as needed.

Hiring a plumber to install a toilet

Toilet installationor, specifically, an S-trap toilet bowl is not the most complicated of tasks. However, trying to do it yourself without the required skills can be fruitless. If you want to be sure that your vent system is installed correctly, you should hire a plumber.

Plumbing vent regulations can be complex, particularly when you consider the fact that some jurisdictions have their own standards in addition to the criteria set by the IPC and UPC. That way, you won't have to worry about failing any necessary inspections.

(Video) How To Vent & Plumb a Toilet (in 2022)

Althoughtoilet facilitiesThey aren't that time-consuming, there are usually complex plumbing jobs, so it's best to plan on a day or two of work and anywhere from $500 to $1,000 in fees. Licensed plumbers charge at least $65 an hour on average.

If you are in the process of renovating or building a new home and the walls are exposed, you or a professional can complete the job in less time. In any case, the assurance that comes with a professional installation is often worth more than the added cost.


How do you install an S type toilet? ›

Locating the S-trap toilet pan

Align the toilet pan so that the vertical waste outlet fits into the pan connector on the floor. It should create a water-tight seal. Once in place and level, you then need to screw, or bolt your toilet pan to the floor using the secure fixings provided.

How far from the wall is the S-trap toilet? ›

S-trap set-out measurement

For an s-trap toilet, the measurement is taken from the wall to the centre of the waste pipe. An s-trap toilet usually requires a set-out of 140mm. Your existing set-out measurement needs to be within 20mm of the proposed set-out measurement to avoid modification to your existing plumbing.

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

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.

Should you put a trap under a toilet? ›

All plumbing fixtures need to have a trap. Inside a p-trap is 2-4 inches of standing water. This standing water is called the trap seal. The trap seal is what blocks sewer gas from invading into your home.


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