How to Connect Waste Pipe to Soil Stack

A wastewater pipe transports greywater from your sinks, shower, washing machine or bath. On the other hand, a soil pipe transports soiled water from toilets, urinals and bidets.

How your property manages waste will depend on its age; older buildings typically feature two stacks with each stack combining and exiting into a sewer, while newer homes typically utilize only one system with an internal soil stack.


Drainage and waste systems are essential to any building; they keep airborne pollutants out, reduce the likelihood of blockages or leaks, provide proper ventilation, and help to prevent flooding. In order to connect a waste pipe to a soil stack, there are several necessary steps that must be taken.

First, prepare your soil stack and waste pipe by making sure they are the appropriate sizes for each other. Furthermore, check that they are securely connected and fitted out for use.

Once you decide where your pipes will go, it’s important to consider the materials used for connecting them together. If installing a new system, opt for high-quality UPVC materials as these are known to be both long-lasting and cost-effective when dealing with residential drains.

Another factor to consider is the age of your property. If it was constructed or renovated before 2000, then calling in an expert for inspection might be wise. These buildings could still contain elements of asbestos which poses a serious health and safety risk to those living in or working on them.

Finally, you must decide the location of your pipes and whether you want them underground or on the surface. If opt for the latter option, ensure they are protected from damp and humidity to avoid corrosion.

Once all materials are prepared, you can begin drilling your holes. This step is essential as it guarantees the hole has the correct diameter.

Drill a hole large enough for the soil pipe to fit through, yet not so large that it becomes difficult to secure with screws. Additionally, trace around the circumference of the pipe so you don’t create any gaps in its interior.


A waste pipe is a type of drain line that connects from your toilet, sink, shower or washing machine to your soil stack. This long vertical pipe sits outside your home and transports soiled water and other solids to the sewer system.

Typically, this vertical pipe measures 4 inches in diameter and extends above your roof. At its bottom end, it connects with another soil stack that goes underground to form part of your main sewage system.

Soil pipes are designed to transport soiled water from your toilet, urinal or bidet (blackwater) to the sewer. Additionally, they carry sediments like uratic salt that may accumulate in the soil stack and cause blockages.

These pipes can be made of a variety of materials, such as cast iron. While these were once popular in older properties, more modern soil pipe systems that use plastic and other materials are now replacing them.

To connect a waste pipe to a soil stack, you will need a waste pipe connector or boss adapter that reduces it down to the size of your soil pipe. Additionally, an access plug should be added at one end so you can easily clean out any blockages in the waste pipe.

Generally, it’s best to hire a professional drainage company for repairs and maintenance of this type of plumbing system. This is because there can be numerous issues with these pipes, such as structural damage.

Furthermore, waste pipes can become blocked with various items such as grease, oil and non-biodegradable products.

Maintaining waste pipes and soil stacks on a regular basis is essential to prevent them from becoming blocked or clogged. Doing this can prevent costly, inconvenient blockages that could pose major problems with the sewage system.

Boss Connection

Soil pipes transport soiled water from toilets, urinals and bidets (if you’re fancy). Waste pipes carry greywater from sinks, showers, baths and washing machines. It’s essential to know your soil and waste pipes’ differences because they will need replacing or repairing at some point.

Boss Connection: Connecting your waste pipe to a soil stack using a boss connection is the most common and straightforward method for doing so. These can be purchased from most plumbers’ merchants and adjusted to fit any size waste pipe with the aid of a boss adapter.

When selecting a boss connection for your property, there are various types to choose from depending on what suits your needs and the age of your building. Some are straightforward and can be handled by anyone with basic DIY skills; while others require professional handling.

One type of boss connection is a’strap on’ boss, which fits around the exterior of the soil pipe and already has premade boss connections attached. These ends of the strap must then be screwed together for simple installation – but if your system requires more than just a boss connection then calling in an expert plumber may be necessary.

An alternative boss connection is an ‘ORB’ connection, which utilizes an o-ring boss seal for a strong and watertight seal. These connections are commonly used in hydraulic systems but also work great with vacuum pumps and compressed air systems.

When connecting your waste pipe to a soil stack, it is essential that it creates a watertight connection. Furthermore, make sure the waste pipe does not contaminate the soil pipe.

There are a few ways to guarantee this is done, but it’s worth calling in an experienced plumber before beginning any work. This is particularly pertinent if your property has an older system which could still contain asbestos, or an external soil stack running up the side of your house.

Access Plug

When it comes to drain and waste pipes in modern residential plumbing, there are several important features you should be aware of. The primary ones include how they’re vented and what type of connection they utilize.

Soil pipe systems are designed to vent through the roof of your home, allowing gasses produced by bodily wastes to escape into the atmosphere. This prevents unpleasant gases from building up in drain traps and causing issues.

Bodily wastes produce methane and other gases that need to be vented before entering your sewer system. This process is known as a DWV system, or drain-waste-vent.

A DWV system also vents out the water that drains through sinks, showers and toilets. This allows air to enter into the pipes to maintain consistent pressure throughout the whole system, helping individual drain traps maintain their water levels and avoiding vacuum buildup that could pull up liquid from taps.

Installing this type of system correctly is essential in order to meet regulations and avoid issues. Unfortunately, it can be challenging to do so on external soil stacks since they usually need to be placed above the eaves.

An alternative option is installing an air admittance valve, which lets gases escape from the top of a soil pipe but does not prevent pressure issues in your waste pipe. This solution typically applies when terminating the soil pipe inside your property – which can be difficult.

However, it can be an effective solution in many cases. The downsides include that it’s a messy job and requires lots of work at height, so hiring a professional is recommended.

Once you’ve selected the ideal waste pipe for your soil stack, it’s time to connect it. This may be done in several different ways depending on the property layout and available connection types.

1. One of the simplest methods is to use a boss connector. These fittings fit into soil pipe runs and come with pre-made boss connections already attached.

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