Drainage systems are an essential part of any infrastructure. Manmade residential drain systems are designed to remove excess water from a property, not only to prevent serious flooding and foundation damage, but also to keep the surrounding environment safe from issues such as soil erosion.

Surface water and groundwater collect in different locations on a property: on top of the ground, underground, and on top of structures. Because of this, there are different types of drainage systems to target these different areas, ensuring all the excess water is removed.

It’s helpful to know which drainage system or systems you have on your property, just in case something goes wrong or anything needs to be addressed or changed in future. In this article, we’re going to explain the different types of drainage systems, their benefits and drawbacks, and how to identify which your building uses.

What are the different types of drainage systems?  

There are three main manmade types of property-level drainage systems: surface, subsurface, and roof systems. Each is designed to collect and move excess water from specific areas of the property.

These are different from the mains systems, which are public surface water and sewage networks for carrying surface water and wastewater away from properties. The drains we’re discussing in this article typically lead into the public surface water mains drainage network, bodies of water, or soakaways.

Let’s take a look in more detail at the property-level drainage systems.

Surface drainage systems

A surface drainage system is designed to remove water from the top surface of an area. These systems work by allowing water to flow into a typically shallow channel or a series of channels that lead the water to a nearby waterway or designated drainage area.

Surface drainage systems are commonly used in urban areas, where impervious or water-repellent surfaces, such as concrete and asphalt, prevent water from being absorbed.

The benefits of surface drains

• Effective water removal: Surface drainage systems remove large volumes of water quickly, reducing the risk of flooding and water damage.
• Easy maintenance: These systems require regular cleaning, but it’s a quick and simple task. Just remove the top (typically a grate), clear the entry of any debris such as leaves, and flush it with a bit of water.
• Cost-effective: Surface drainage systems are often the most cost-effective drainage option, particularly in areas where subsurface drainage is not necessary.

The drawbacks of surface drains

• Limited infiltration: Surface drainage systems do not allow water to soak into the ground, which can lead to increased runoff and erosion if the water starts to overflow a surface drain’s capacity.
• Limited effectiveness in heavy rain: These systems may not be able to keep up with a high volume of water, such as rainwater from continuous heavy storming, resulting in flooding or water damage.
• Dependence on slope: To function effectively, these systems need a slope so that gravity can create momentum – a surface drainage system may not work in areas with flat or low-lying land.

Subsurface drainage systems (French drains)

Subsurface drainage systems, also known as French drains, remove water from the soil deep below the surface. These systems work by collecting water in underground pipes or channels and directing it to a designated drainage area or waterway. Most subsurface systems utilise various components, including perforated pipes and drainage trenches with gravel and fabrics acting as filters.

Subsurface drainage systems are commonly used in agricultural land, sports fields, and construction sites.

The benefits of subsurface drains

• Increased soil aeration: These help increase the amount of air in the soil by removing excess water, improving plant growth and reducing the risk of soil erosion.
• Reduced water-logging: Subsurface drainage systems help to reduce the risk of water damaging crops and reducing yields.
• Effective in all weather conditions: As these systems are built underground, they are incredibly reliable no matter the weather.

The drawbacks of subsurface drains

• Expensive installation: Subsurface drainage systems are more expensive to install than surface drainage systems, particularly in areas with hard soil or rocks, due to the deep excavation work and specialised materials required.
• Maintenance requirements: These systems require regular maintenance with specialised equipment to prevent clogging and ensure effective water removal.

Gutter and downspout systems

Also known as roof drainage systems, gutters and downspouts are designed to collect and transport rainwater and snowmelt that falls on a building’s roof. These systems are typically found on commercial or residential buildings to prevent excess water from causing water damage to a building’s structure and foundation. Roof drainage systems are made up of gutters, downspouts, and other components.

The benefits of roof drains

• Prevents water damage: By collecting rainwater and channelling it away from the building’s foundation, roof systems prevent flooding and water damage to walls and ceilings.
• Protects the foundation: A roof drainage system can help protect against soil erosion, which leads to foundation damage and potential structure collapse.
• Increases the lifespan of the roof:  By preventing standing water, gutters and downspouts help extend the lifespan of a roof.

The drawbacks of roof drains

• Potential for clogging: If not properly maintained, roof gutters can become clogged with leaves, twigs, and other debris.
• Regular maintenance needed: Regular maintenance, including cleaning and inspections, is necessary to keep the roof drainage system functioning properly.
• Ice dams: In cold weather, ice blockages can form in roof gutters and piping, causing water to back up and cause damage.

How to identify your drainage systems  

There are several ways to identify your drainage systems, but we always advise consulting an expert to avoid mistakes or unnecessary risks. However, before you talk to a drainage company, you can gather preliminary information by doing the following: 

• Arrange a CCTV drain survey:
  • For absolute, concrete certainty, the best way to identify which drainage systems you have is to invest in a CCTV drain mapping survey. This way, a professional team can see if your system is connected to the mains or soakaways, along with other essential drain network details. You’ll receive an in-depth report once the survey is complete, analysed by water authority-approved software. We can assist you with understanding these results, and will offer advice and recommendations for next steps.

• Look for surface indicators:
  • Surface drainage systems usually have manhole covers (easily confused with foul water manhole covers) which are easy to spot. Other surface signs include grates, aco channels, and air vents (which are typically over attenuation tanks).
  • Subsurface drainage systems are a little harder to spot, but typically you’ll be made aware of them when purchasing land. They can sometimes be indicated visually via manhole covers, grates, gravel troughs, and pipes leading into/out of the ground.
  • Roof drainage systems are very easy to spot, as they’ll run along the edge of the roof and down the building to empty rainwater into a grate or caped rest bend. (usually a surface drainage system).

• Look through property deeds and plans:
  • If you’d like to look at your property deeds for evidence of drainage, you can typically access the physical copies through your solicitor, or pay for and download a digital copy via the Land Registry. These plans may detail your drain system, but could possibly be out of date.

Why it’s important to know what drainage system you have

It’s really useful to know which drainage systems you have on your property for several reasons.

First, it’s helpful when something goes awry to know what could be causing it. Knowing the systems on your property and where they are can help you identify an issue far sooner than if you were completely unaware. If you notice a blockage or foul odour, knowing which drain pipe is which can help you identify if it’s a rainwater or wastewater issue, enabling you to contact the right people with a good base for your enquiry.

Second, understanding your drainage systems, including the mains systems carrying wastewater and all that collected surface and groundwater away, means you can help prevent environmental pollution. If you want to build a new bathroom, you need to know where your new plumbing should connect to avoid sending foul water into the surface water system and polluting the local river. If you want to install a new patio and you connect its runoff into what you think is a general drain but is actually the sewage drain, you’d be responsible for rainwater overloading treatment systems.

How to choose the right drainage system for your property

When it comes to choosing the right drainage system for your property, the best solution is to ask for advice from drainage experts. Without their expertise, you’d need to assess the type of property you have and its drainage needs, which can be confusing if you don’t have the experience.

If you are a developer, it is important to consider sustainable drainage systems (SuDS) as a legal requirement. Don’t forget to look into local water authority requirements and charges before planning any new drainage systems.

It’s also important to consider the cost and maintenance requirements of different types of drainage. A professional drainage service provider like Premier Drainage Solutions can help you evaluate your options and choose the best drainage system for your property.

Need help with your drainage system? Contact us for further information.