Flushing out what lies beneath: why we need to talk about sewers and drains

Flushing out what lies beneath: why we need to talk about sewers and drains

When you buy a property, your solicitor will undertake searches before you commit to your purchase. These searches include a water and drainage search to, ahem, flush out information including whether there are any public water mains or sewers running under the property. The search will include plans showing any public water mains or sewers within the property.

Why does this matter?

Apart from the fact not many people would like the thought of a sewer running under their kitchen or dining room, it matters because the water authority has statutory rights of access to public sewers to maintain and repair them. To put it bluntly, you would not want to see your floor taken up by the water authority to carry out work to the public sewer running beneath it.

No-one should build over or very close to a public sewer without first obtaining the water authority’s consent, known as a Build Over Agreement. The water authority will want to check that they will still have sufficient access to repair/maintain the public sewer and also that the weight of the building won’t damage the public sewer.

Any building constructed over a public sewer without having first obtained the water authority’s consent may have to be removed or altered. This could be potentially very expensive for the property owner.

Water authorities do not allow property owners to build over or immediately next to public water mains. Firstly, as with sewers, they will be concerned about being able to maintain access to the water main. Secondly, if the water main bursts, this has the potential to cause major structural damage to the building above it.

What can I do?

A buyer should always have a structural survey done before they commit to buying a property. If your legal adviser indicates that part of the property has been built over a public sewer, then make sure you show a copy of the water and drainage search to your surveyor so they can advise you on the practical implications of this.

Where the building has been constructed without obtaining a build over consent, usually the seller will be asked to provide an indemnity insurance policy. These policies are available for a one-off premium and can be put in place quickly. They will protect the property owner and their lender from financial losses which they suffer because a building was constructed over a public sewer without first obtaining the water authority’s consent. However, usually the policies are time limited and they will only cover a pre-existing building built over a sewer, not a new one.

Another option would be for the seller to ask the water authority for a retrospective build over agreement confirming their consent. The risks to the seller are firstly this will inevitably delay the sale going through and involve incurring costs. Also, the water authority may refuse consent. Once the water authority has been approached to give consent, title indemnity insurance will no longer be available.

What if I am thinking of extending or rebuilding the property?

If you think you may want to extend or rebuild the property after buying it, firstly make sure your legal adviser knows this.

Also, you should show a copy of the water and drainage search to an architect so they can advise whether you are likely to need to either relocate the extension or have the public sewer diverted so as to avoid building over it. In either case, this is likely to increase the costs of the extension/building work. You should also consider a services survey to establish the location of any other utilities crossing the property which may be affected by your proposed extension/rebuilding work.

A final point to think about is that the water and drainage search only shows the location of public water mains and sewers and also it may not be accurate.  For example, there could be private sewers located where you are intending to build which wouldn’t show on your water and drainage search.  Also, there could be public sewers within the property which are not shown on the water and drainage search. There may be other utilities running where you are intending to build – your legal adviser can do conveyancing searches for other utilities.

Alison Munro