Water companies keep up-to-date maps of sewers and water mains for which they are responsible. Most but not all pipes within an individual property boundary are the property owner’s responsibility to maintain. It is important to find out where the drains run on your property and what condition they are in.
Home Buyers Drainage Surveys have become commonplace across the UK. Building surveyors value the information provided by these surveys and often advise clients buying domestic homes and commercial buildings to ensure that they have a drain survey carried out by a fully certified drainage surveyor prior to purchase.
They are also helpful if you are planning a new building or an extension to an existing building. During the design stage of your project, before any work has been done on-site, you need to find out if there are sewers or lateral drains (pipes that carry wastewater from your property to a sewer) close to or beneath the proposed structure.
Doing this early means you can avoid costly delays, unplanned work, or repairs to damaged pipes.
Did you know?
Sewerage companies are responsible for the public sewers. These are usually in roads or public open spaces but may run through private gardens. The sewerage company has a right of access to these sewers for maintenance. If the company carries out work on sewers on your land they must follow a code of practice, which is available from the company.
Property owner’s responsibilities
The drains and any private sewers which carry household waste are normally the householder’s (or the landlord’s) responsibility. This applies up to the point they connect with the public sewers. Since 1 October 2011 (following the transfer of private sewers), this is usually at the boundary of the property. The exceptions to this are private sewers, which only conveyed rainwater to watercourses and some privately owned pumping stations and treatment plants.
Even if you have permitted development rights for your build, you’ll still need permission from your local water authority if you’re building over or close to drains and sewers.
If a public sewer runs beneath or within 3 m of your new-build or extension, you will need to submit a Full Plans application to building control (rather than a Building Notice) and will need to provide evidence of a Build-Over Agreement. There is an additional charge for this agreement, and you should factor in the time it takes to obtain this. Your Registered Building Inspector will need to see the build over agreement before they can issue a completion certificate. The sewer will need to be protected during construction to prevent damage.
How do I find out if there are drains or sewers on my property?
Sometimes, the presence of drains may not become evident until excavation work starts on site. It may be obvious if there’s an inspection chamber or maintenance hole in your garden or patio (if you have a maintenance hole cover), but otherwise, you may be able to find out with the help of your builder, your architect, the legal documentation for your property (the deeds) or your water authority
If there is a maintenance hole or inspection chamber that serves more than one property, you won’t be able to build over it.
What if I can’t find the sewer, or I’m worried about its condition?
CCTV drainage surveys are becoming increasingly popular with surveyors, engineers, contractors, and architects. Generally, an architect will require pre- and post-conditional drainage surveys where a new building or an extension is planned.
The pre-conditional CCTV survey (Pre-con)
The Pre-Con survey is designed to identify the position and condition of the current drainage system at any property which is due to be extended. It will map the drainage layout and identify the drainage system ownership (be that water company, private or a combination of both). It will also help to determine the drain depth and flow direction plus identify pipe size, shape, diameter, and its condition. These are all very important factors for architects in the planning stage and will help them to determine the new drainage system layout and specification.
You may wish to engage a drainage surveyor to comment on the new system layout and design: this is often referred to as the planning meeting, which normally takes place on-site with all parties.
The post-conditional CCTV survey
A post-conditional survey (post-con) may be carried out once the new drainage system has been constructed. This is to ensure the new drainage system has been laid, bedded, and connected correctly by the building contractor and is fit for purpose. It will also ensure that the new system does not have any misconnected drainage, which can cause pollution to the connecting local water courses like rivers, canals, and streams.
The survey can be used to help demonstrate that Part H of the building regulations has been complied with as well as showing that you have built in accordance with any Build-Over agreement.
What if my private sewer is damaged?
Damaged drains and sewers can lead to costly damage to your property. You can fit an entirely new drainage system, but you might prefer to use a drain lining system, which uses no-dig technology for a lower cost, lower impact, and relatively quick form of repairing or replacing below-ground drains and sewers. This is known as Cured In Place Pipe (CIPP). The process involves installing a lining sleeve which bonds to the inside of the pipe, creating a pipe within a pipe, and restoring the integrity of the drain or sewer. Drain relining can be carried out on pipes of any size and can also be used for smaller repairs, where patch liners can be installed to provide a point repair on a single defect or set of defects located within a small area.
Always ensure that you are using fully certified drainage surveyors to undertake this work in compliance with industry best practice and standards. You can find more information on the National Association of Drainage Contractors (NADC) website.
The NHIC wishes to thank WG2 | Consumer Voice members for contributing to this guide.
Please note that this guidance document produced by the NHIC was correct when published. However, information and regulations may have changed since its publication. Therefore, seeking the most up-to-date information and expert advice is always advisable before making any decisions related to improving your home.
