Know your pipe system


Learning more about the layout of your plumbing and piping system beyond the sink can be extremely helpful. After all, these pipes play an essential role in taking water and wastewater to and from the various appliances you rely on every day, so it’s worth knowing how they basically work, in case you ever have to deal with a blockage or another problem.

In this guide, we will specifically discuss the basic functions of the pipes that take wastewater away from your home, as these are the ones that are at risk of being clogged, and therefore require the greatest care and attention to keep them running smoothly.



A complex pipe network

The majority of a property’s wastewater pipes connect to appliances, such as washing machines and dishwashers, to the main sewer pipe that leaves the house and carries the unwanted fluids into the public drainage system.

As well as appliances, these pipes will be connected to the toilet, shower and all of the property’s sinks – meaning that a blockage created in one part of the home potentially poses a risk of affecting the entire home, depending on how far along the system the problem arises.

U-bends and blockages

If you take a look under your bathroom or kitchen sink, you should be able to see a U-bend pipe (although these are occasionally contained within a pedestal or other covering). The U-bend is there to collect water, as well as stop foul-smelling gases from escaping into the home – it is also where blockages often begin, whether this is due to an accumulation of food, hair or soap scum.

The U-bend and other wastewater pipes are not typically very large, measuring around 32mm in diameter, depending on the appliance. As such, even a small amount of solid material can create a blockage very quickly, which is why property owners are advised to be vigilant about preventing non-degradable items and substances such as fats, grease, wet wipes and nappies from entering these pipes.

u-bend waste trap

The pipe shut-off

Should you have a clean water leak, blockage or other problem, knowing where to find the shut-off valve for your house’s water supply can save you a lot of time and trouble, especially if you’re dealing with overflowing water. In some houses, you should be able to turn the water supply off for individual appliances, using the correct shut-off valve next to it.

However, if your home isn’t set up this way, you can also turn the water off for your whole house. This shut-off valve will usually be somewhere on the outside edge of your home, so making a note of its location for future reference is a worthwhile precaution.

water shut off valve

Finding the drain

After a little investigation, you should be able to find the main drain connecting your house to the sewer pipe. There will most likely be a drain cover somewhere outside your home within your boundaries that indicates where this is. It can be useful to know this information, should you need to identify where a blockage in your system is; the location of manhole chambers is also something that’s essential to consider if you’re planning to extend your property.

Bear in mind that these covers are heavy, and harmful gases can lurk inside, so make sure the necessary care and precautions are taken when opening them. If you suspect there’s a problem, it’s usually better to call a professional rather than tackling this on your own – in particular, untrained professionals should never enter drains themselves.


Once you’ve learned the basics of how your piping system works, it’s likely that you’ll have a few follow-up queries about how they work, and how they might need to be looked after when things go wrong. Here are answers to a few frequently-asked questions:

Who is responsible for the drains on my property?

The network of pipes taking water away from your home will connect to a main sewer pipe that will service other homes around you. Under rules set out in 2011 via the Private Drains and Sewers Act, you’re responsible as a homeowner for the sections of piping that sit within your home’s boundaries; as soon as the pipe leaves the boundaries of your home, it becomes the responsibility of your water or sewage company.

This is because the 2011 legislation transferred ownership of most of the private sewers in England and Wales to the utilities companies, with the exception of pipes that exclusively serve a private property. However, there are still a few drains that work on a shared ownership model between several properties, so if you want to learn more about how these responsibilities are decided, click here.

Should you have a blockage or other issue in a pipe that’s within the boundaries, it’ll be up to you to fix it, which is why it’s useful to know more about how they work.

Is my property connected to the mains for foul water drainage?

If your home was built after 1920, it is likely that your property has two separate drains: a foul sewer drain and a surface water sewer drain. This ensures that rainwater can be funnelled directly into a local waterway, while wastewater is taken to the sewage works for processing.

However, it is estimated that around 500,000 UK properties have misconnections, meaning foul water is erroneously connected to the surface water drain, resulting in pollution to rivers and beaches. As the homeowner, you are legally responsible for correcting this issue, so it’s important to make sure you’re able to recognise possible indicators that your property might be at risk. These include:

  • a new manhole within your property, as this means the drainage has been altered
  • new bathrooms, toilets or kitchens added as part of an extension, or water-based appliances installed in garages or other outbuildings, as these often result in misconnections
  • pipes connected to the downpipes from your roof guttering

Where does my surface water drain to?

In most cases, surface water – which is simply rainwater that runs off your property’s roof and paved areas – is collected by drains and gullies that flows into a public sewer. Because these sewers are operated by local utility companies, most people are charged for the cost of surface water drainage through their sewerage bills.

However, if no rainwater drains from your property into the public sewer system because you have a soakaway – or if all the surface water from your home drains directly into a watercourse, brook or stream – then you don’t have to pay this charge. If you think you’ve been paying for this service in error, then you can apply for a rebate, in addition to having money knocked off your regular bill.

To find out whether you may be eligible, then get in touch with your local water company and investigate further – it’s possible that you could be due a significant saving.

How do I find drainage plans for my house?

There are many reasons why a property owner or resident might need to find out where their drains run. For example, you may be planning an extension, or you may require this information in order to carry out essential repairs to your pipes.

To obtain these plans, you have a number of potential options:

  • Contacting your local water authority or regional council – please note that these organisations will usually charge an administration fee to provide the necessary information
  • Making use of the free-to-use LSBUD service, which can provide schematics on request for hundreds of thousands of kilometres of underground and overhead pipelines and cables across the UK
  • Getting in touch with the previous property owner, who may have already obtained the drainage plans and can pass them along to you

If you are looking for a more detailed view of how your drain or sewer line runs, it may also be possible to organise a CCTV survey, allowing you to find out more about the layout and condition of your drains.

How can I find out more about my piping and drainage system?

If you’d like a detailed plan of the utilities infrastructure of your property, services such as free-to-use LinesearchbeforeUdig can provide schematics on request.

For more information about your plumbing system, sewer arrangements and drainage responsibilities, you can also get in touch with your local water and wastewater services supplier directly. Click through below to reach the contact page of your supplier:

If you’d rather speak to someone right away, call our 24/7 team on 0800 526 488.

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