What are The Types of Drainage, and How to Tell Them Apart?

Knowing the different types of drainage systems, and discovering which one is on your property, can help you massively in the future. If you ever need to make any changes to your current drainage system, either due to a fault or because you need to add drainage to a new extension, you’ll need to know which types of drainage system you have and what they do. This is so that you can safely make changes to your current system without any guesswork – preventing any hazardous cross-contamination. 

What are the Different Types of Drainage?

What is drainage and what are the different types of drainage? In the UK, most homes have just two residential drainage systems. These are typically made up of two different types of pipework which are often referred to together as the mains drainage. The reason these two systems of pipework are kept separate is that one contains surface water; which takes away rainwater, runoff from roofs, downspout, and gutter systems. The other is used for foul water: removing water from toilets, showers, and even washing machines. 

Residential drainage systems are designed to remove excess water from residential areas – helping to remove this excess water from walkways, driveways, and roofs in order to prevent any risk of flooding. They also assist in preventing rotting, mould, mildew, and structural damage in buildings that can be caused by a buildup of water. 

Residential drainage solutions often consist of:

Surface Drainage Systems

Surface drainage systems are made up of shallow ditches dug in a parallel pattern. These ditches act as canals for surface run-off water. They also direct the water into the main drainage system to prevent any form of water pooling and flooding. 

Subsurface Drainage Systems

Also known as a French drain, subsurface drainage systems are located beneath the top layer of soil in order to remove excess water at the root level. Subsurface drainage systems also require the creation of deeper ditches and the installation of underground pipes which will lead to a large collector drain – designed to collect any water from the underground pipes. 

Slopes

Slope drains allow excess water to flow downward from a structure with the help of pipes moving down a slope. A pipe is installed and then connected into a small incline; allowing water to flow through the pipe and away from the structure. 

Downspout and Gutter Systems

Downspout and gutter systems collect water from gutters and direct it to the ground. A downspout is usually connected to a gutter system on a building, carrying water away from the roof straight down to the ground. This all happens on a slope, preventing water from pooling below. 

Residential drainage systems may have pipework, such as a twinall or land or surface drainage, and this water drainage will never be discharged into a septic tank. This water is returned into watercourses and can be very dangerous if mixed with foul water. 

If you have a soakaway crate in your garden, it will hold this water and gradually percolate back into the ground at a suitable rate – ensuring that it doesn’t pose a danger to the local environment or public health. If you find that you have an attenuation crate in your garden, which is similar in appearance to a soakaway crate, this will remove excess water and redirect it into a watercourse or a predetermined area that has been deemed suitable for drainage. 

The only place foul or wastewater should be discharged is into the main sewer drainage system and drainage pipes, where it can be treated in a sewage treatment plant before being safely returned into the water system. If you’re in a rural property, you may have a septic tank or cesspit buried in your garden which also aids subsurface drainage. 

Identifying Your Drainage Systems

There are multiple different types of drainage systems in the UK, all found on different types of property. Below, we describe each type of drainage system that may be on your property – and how to identify each one in the easiest way possible. 

Manholes

If you have twice the number of manhole covers as a conventional property, it is most likely that you have a dual drainage system. This type of drainage system carries away soil and wastewater to where it can be treated safely. 

Property Age

Newer properties, namely those built after 1969-1971 will typically have a dual drainage system. Older homes, built before the 1970s, can usually have separate pipes for soil and waste. 

Watch the Water

Run a tap or flush the toilet, watching the water from an open manhole cover and seeing where it flows will show you which pipework the water runs through is your foul water drainage system. 

Run a Hosepipe

By running a hosepipe down your drainpipe and watching where the water runs will show you where your domestic/residential drainage system is. 

Rural Areas

If you have a drain cover in your garden that is raised and has an electric box outside, this will mean that you have a sewage treatment plant on your property.
If you have just one manhole cover above ground, then it is more than likely that you have a cesspit in your property – this will need to be emptied very regularly or replaced with a septic tank in order to prevent any potential damage to the local environment or public health.


If you find that you have between 2 and 4 manholes in close proximity to one another, and vent pipes above ground, this signifies that you have a septic tank on your property.

Your Responsibilities Regarding Your Drainage System

As the owner of a property, you are solely responsible for the drainage system on your property. This includes any problems that your drainage system encounters, such as blockages and overflow, right up until the water enters the main sewer system. 

If you create a blockage on your property, you will have to fix this at your own expense. However, if there is a blockage further down into the main sewer system; it will be the responsibility of your local authority. If you try to change the pipework for your foul drainage system, there are potential high health risks – so before making any changes, please refer to your local authority, local building control office, or the experts at Coastal Drains. 

Need to get in touch regarding sewer system responsibilities, or to identify your drainage systems? Contact us here

Author: Greg Child

Greg is an expert in drainage and has been in the business for over 30 years. He's the owner of Coastal Drains Ltd and a very, very friendly chap.