Types of drain

Drains, sewers, lateral drains, surface water, foul and combined; these are just a few of the terms used by engineers to describe what most people would call ‘the drains’. So what do these terms mean and why are they important?  

Below is a short summary of what engineers mean by each of these terms.  


A pipe which serves 1 property only; this includes surface water, foul and combined drains. 

Lateral drains 

A pipe which only serves 1 property but is located outside the property boundary.  


These are larger pipes serving more than 1 property with many drains or lateral drains connected to them. They are sometimes called ‘Public Sewers’. 

Highway Drain 

These are surface water drains which drain adopted highways.  

Private roads and driveways are not usually connected to Highway Drains. 

Surface water 

These pipes contain rainwater only, and are sometimes called ‘Storm Drains’. 


The pipes contain waste from kitchens and bathrooms etc.  


These pipes contain surface water and foul water. Any combined pipes are usually older as latest guidance tries to avoid using them.  


The type of pipe and where it is located affects who is responsible for making sure it’s working properly. Below is a summary of who is responsible for what.  


Land owners 

Lateral Drains 

Water Companies (Southern Water or Thames Water) 


Water Companies (Southern Water or Thames Water) 

Highway Drains 

Highway Authority (West Sussex County Council) 

Water Companies became responsible for lateral drains and shared drains following the Private Sewerage Transfer Regulations in October 2011. Lateral drains may not be shown on a public sewer plan and you may need to confirm where your drain becomes a lateral drain yourself.  

Water Pipes

In Mid Sussex drinking water is provided by a separate company to the surface water and foul water sewers. Drinking water is provided by South East Water or Southern Water. If you suspect a mains water pipe has burst, then this should be immediately reported to the relevant water company.  You can find your water supplier by following the link below. 


Emergency Contacts

Southern Water – Emergencies: 0330 303 0368 
Thames Water – Emergencies: 0800 316 9800 
Highway Authority – Emergencies: 01243 642 105 
South East Water Emergencies: 0333 000 0365 

Historic Drainage Plans

Mid Sussex District Council may hold historic drainage plans for your property but there is no requirement in law to keep plans of private drainage systems. These plans are often from historic planning records and may not be up-to-date or as built, and not all properties in the district will have drainage plans available.  

To find out if there are any plans available please contact:  

The Flood Risk and Drainage Team 
Email: drainage@midsussex.gov.uk  

Last updated: 21 August 2023