A Guide To The Types of Drainage

Understanding the different types of drainage is essential for managing properties effectively and preventing costly issues. Across the UK, systems can vary from foul and surface water drains to combined sewers and Sustainable Drainage Systems (SuDS), each with its own role and responsibilities.

In this guide, Express Drainage Surveys explores how these systems function, who is accountable for their upkeep, the problems they are most vulnerable to, and the situations where a CCTV drainage survey is the most appropriate course of action. We also outline the key legal factors you should be aware of when dealing with drains.

The four main types of drains

Foul water drainage: carries your waste from toilets, sinks and washing machines out and away to private treatment facilities.
Surface water drainage: deals with the run-off of rainwater from your driveway, patio, roof and your land in general.
Combined sewer systems: – a single pipe which carries both surface and foul water, found more in older urban areas and most often associated with overflow events.
Sustainable Drainage Systems (SuDS): this is a collection of measures, such as permeable paving and green roofs, designed to manage rain run-off at the source.

Foul water drainage – what is it and what are the typical issues?

Foul water drainage is the sewage from your toilets and sinks, as well as the grey water pumped out of your kitchen appliances. Your foul water drain will enter the public sewer, with the foul water from all other properties, before reaching a sewage works. You can find guidance on what makes adequate foul water drainage in Approved Document H of the Building Regulations.

Common problems with foul water drainage: The thing you most commonly find that goes wrong in this system is repeated blockages from fat, grease, oil or root ingress. This creates a backup inside the property.

Surface water drainage – what is it and what are the typical issues?

Surface water drains are what carry rain from your roof, paved areas and general garden space. Drain components typically include gullies, channel trenches, soakaways and permeable paving. This water has to be kept separate from foul water to help lighten the load on treatment works. You can also find best practice guidelines in Approved Document H for this drainage type.

Common problems with surface water drainage – Because this drainage infrastructure is there to protect your property, any silt or debris blocking any of your surface drains will lead to the system overflowing and flooding the foundations or basement of your property.

Combined sewer system – what is it and what are the typical issues?

For older infrastructure, such as in towns and cities, there may be combined sewers that take both foul water and surface water in one system (hence the name). This largely happens when there is a deluge of heavy rain and overflow points take additional surface water to protect property.

Common problems with the combined sewer system – The greatest issue with this drain type is that it leads to the contamination of the environment due to the combination of foul water and rainwater.

Sustainable Drainage Systems (SuDS) – what is it and what are the typical issues?

Sustainable drainage systems – also known as SuDS – can mimic natural drainage by slowing down, storing and treating any run-off closer to the source. This helps to reduce the flow of water at peak times in sewers, improves water quality and benefits biodiversity. This is becoming more commonly implemented in new, larger developments with lots of hard surfaces.

Common problems with SuDS – Maintenance for these systems is absolutely essential, as any debris, foliage and litter can reduce how effective it is in the long run.

Additional drain types you may have heard of

Soakaways: These are buried chambers that help to collect rainwater and allow it to slowly drain back into the surrounding soil. They require siting and installing correctly in order to ensure they can accept water quickly enough.
French drains: These are a sloping trench drain filled with coarse stone over a perforated pipe. This is used to intercept groundwater and surface water to direct it away from a building’s foundations.
Trench or channel drains: These are usually found on driveways or paved areas and are used to collect surface water to direct it towards the general drainage system.
Sump and pump systems: Where an area is below ground and requires draining, a sump pump may be needed. This will require regular maintenance and a reliable power source, installed by a qualified contractor.

Who is responsible for which drains?

We’ve covered this topic in plenty of detail in our previous blog posts, but a general rule of thumb is that any drain within your property boundary is your responsibility for maintenance and repairs. Meanwhile, any drains outside of your property boundary are commonly taken care of by private water companies.

If you’re faced with a blocked drain but you’re not sure exactly where the blockage is and who is responsible, you can always have a CCTV drain survey carried out. Our professional CCTV surveys can pinpoint any issues in your drain so that you can be clear on who is responsible.

Professional services for your drains

Knowing which type of drainage you have – foul, surface, combined or SuDS – is the first step in protecting your property as well as the environment around you. Early diagnosis and a proactive approach can help lower the risk of flooding and pollution.

If you suspect that there is a problem with your drainage or if you need a documented condition report, at Express Drainage Surveys, we provide a variety of services using the latest technology and equipment to help you look after your system. We can provide comprehensive quotes and assistance for any maintenance or repairs required. You can explore more of our services on the rest of our website, including:

Need expert assistance with your particular drainage system? Look no further. Contact our dedicated team today and we’ll help you to manage any issues or record any information you need for your drains.