The down-low on drainage and sewage
Craig Burman, head of Environmental and Regulatory at Schofield Sweeney Solicitors LLP, demystifies all things drainage and sewage – revealing everything homeowners and tenants need to know to help keep...

Craig Burman, head of Environmental and Regulatory at Schofield Sweeney Solicitors LLP, demystifies all things drainage and sewage – revealing everything homeowners and tenants need to know to help keep their systems in check.

I’m the first one to agree that it’s very hard to make sewage and drainage exciting. But on the other hand, I have seen plenty of excitement caused by sewage and drainage that has gone wrong.

We really don’t like to think about it. We push a flush or turn on a tap and expect our plumbing to deal with the consequences. And most of the time, it does what it should. However, with heavier rainfall and rising water levels, this is not something we should take for granted.

As a general rule, the property owner – or tenant – is responsible for maintaining the pipework within the boundary of their property. Blockages must be cleared at their cost and normally by their contractor. Many of us have learned through bitter experience that flushable wipes are not that flushable and tree roots can find their way into most clay pipes.

Where two or more properties are connected, even on private land, the drain is likely to be a “lateral drain”, which must be maintained by the water company. If your neighbours drain across your land, it may not be your responsibility to maintain these drains or sewers.

If you’re lucky enough to be connected to mains sewerage, the waste from toilets, sinks, showers and baths will go via a system of sewer pipes to a waste water treatment works.  Once outside your boundary, pipes normally become the responsibility of your water company.

There are, however, exceptions to this rule.

Did you know?

Properties not connected to mains sewerage systems will often have a septic tank, sewage treatment plant or a cesspit that allows solids and liquids to separate. Liquids will be discharged to ground, or a watercourse, and solids are pumped out periodically. This is normally the property owner’s responsibility to maintain and operate. It’s not unusual for multiple properties to be connected to the same sewage treatment system, and all share the cost.

Some commercial and residential developments have a private sewage treatment plant installed by the developer. Many of these are adopted by the water company when the development is complete, but some remain in private ownership and properties using them have to contribute to their upkeep. These are known as private sewers and sewerage systems.

The Victorians thought it was a good idea to combine surface water and sewage into one system, called a combined sewer overflow, or CSO. It combines clean rain water and untreated sewage to take it to the local sewage treatment works. This means everything from a property goes to in a single pipe to the same place.

If you don’t have a CSO, or don’t live in an area without mains sewerage, surface water from rooves, driveways, patios and hard surfaces normally goes into private drains on the property – which are the owner or occupier’s responsibility. Once outside your boundary, surface water pipes are the responsibility of either the local authority, the highway authority or the water company, depending on the type of drain. Many of these find their way into a river or stream.

I think it’s fair to say that most of us have no idea where our surface water drains end up – and why should we if they are not our responsibility? That said, let me give you three very good reasons why you should be inquisitive about your surface water drains.

Risk of flooding

When river levels rise, two things can happen. Drain outlets can become submerged and the drain stops discharging, or water travels backwards up the drain system, due to the force of the water at the outlet. Either way, it is not good news for anyone upstream.

Faced with an obstruction, water will find its way out of the system where it can. Flooding around manholes and drainage grates often occurs. I always used to think it was because there was too much water trying to get in, but often it’s the water already in the system trying to get out. Sometimes it’s both.

Once water starts coming out of drains, it’s extremely difficult to stop it. It will find low lying areas and many properties have been flooded due to drains being overwhelmed by the volume of water.

Those of us who haven’t been flooded before should not be too complacent. Drains that block will often cause the same issues. If you notice water sitting around a drain where it doesn’t normally do so, don’t ignore it. It may be a sign the drain has blocked or collapsed downstream.

Combined sewer overflows

You may have seen in the news the problem of sewage discharging into rivers during heavy rain. Believe it or not, CSOs are designed to do this. 

The major flaw with CSOs is that during heavy rain, the system is overwhelmed by the volume of water and the sewage treatment works cannot cope. At a certain flow, the mix of sewage and surface water is intentionally diverted to a river or the sea. The sewage should be diluted by the rainwater, but often its still enough to cause pollution. 

CSOs will occasionally spring a leak or discharge outside storm conditions. This can be very unpleasant. If you are unlucky enough to be flooded by this murky cocktail, it will contaminate everything it touches, inside or outside. For most of us, it’s a very nasty surprise. 

It can also be a surprise to property owners that they cannot normally sue a sewage undertaker whose assets are causing flooding or contamination. If the damage is caused by the condition or capacity of the sewage network, the Water Industry Act 1991 sets out a scheme of compensation.

Anyone aggrieved by such impacts needs to use the compensation scheme and/or ask the relevant Secretary of State to make an enforcement order requiring upgrades to the system.    


Surface water drains that go to a watercourse have the potential to cause pollution. 

I have represented many businesses who have a spill or incident and find their yard drains have taken pollutants to a local watercourse, with disastrous consequences for fish and aquatic life. Prosecutions by the Environment Agency for this sort of pollution are not uncommon.      

But it’s not just chemicals which cause pollution. Milk and silt are also harmful to aquatic life by lowering oxygen levels in the water. Wet concrete is very alkaline and can have a big impact on pH levels.

If you deal with any kind of pollutants, I recommend you have up to date drainage drawings and plans in place to prevent pollution.  


It sounds like doom and gloom, but most drains and sewers work as they should. When they don’t, it can cause a lot of stress and anxiety – especially when it rains heavily. To minimise any unpleasant experiences, I suggest the following to property-owners:

  1. Know where your stopcock is and make sure it is working and can be turned off
  2. Don’t flush your wipes –  even if they say they are flushable!
  3. Maintain manhole covers and inspection chambers so they can be accessed easily
  4. Keep an eye out for standing water or flooding – and act quickly if you see it
  5. Know where your drains are and how to clear them if they become blocked
  6. Have a drainage plan or sketch, showing what is going where. You can ask for these details from the local authority or water company (there may be a charge)
  7. If you have previously been flooded, or you are in a low-lying area, find out what flood resilience measures will lower the risk of future flooding
  8. Keep emergency contact numbers somewhere safe!

Craig Burman is Head of the Environmental and Regulatory at Schofield Sweeney Solicitors LLP. Craig specialises in flooding, drainage and water management issues and can advise on a wide range of water and drainage related issues.

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Posted 6th February 2024

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