Building near public sewers

• What is a public sewer?
• How do I know if there is a public sewer on my property?
• What happens if I do have a public sewer on my property and want to carry out building work?
• New legislation on sewers

If you are carrying out building work to your property, you will need to consider whether the building work will affect a public sewer. Part H4 of the Building Regulations imposes certain controls over what can and can’t be done if building work will fall within 3m of the sewer.

What is a public sewer?

A public sewer is any drain which is in the ownership of the water authority, even though it may pass across your private property. A public sewer can be any size. Often sewers which cross private properties are relatively small (perhaps 100mm in diameter) and not very deep.

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How do I know if there is a public sewer on my property?

This may have been highlighted by your solicitors when you purchased the property, though you may not have realised its significance at the time. If you are unsure, you can contact the relevant water authority to find out whether a drain crossing your property belongs to them or whether it is your private drain. In Herefordshire the water authority is either Welsh Water or Severn Trent Water. You can also contact one of our surveyors for advice.

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What happens if I do have a public sewer on my property and want to carry out building work?

If it is within 3m of the work you are carrying out, you should contact us to discuss. You should not proceed with any building work until agreement has been reached, as there may be special measures you need to incorporate in the works in order to protect the sewer from any long term damage.

We will consult with the water authority for our own purposes and keep you posted of any developments. However, the obligation to properly explore the matter does lie with the property owner, so you should also contact the water authority yourself to establish exactly what is required. We would not advise that you rely on our consultation.

The water authority will assess the sewer and make a judgement about how important it is as part of their network of drains. In some cases, they will give permission for the work to proceed, simply requiring you to follow the normal standards of work required by the Building Regulations. In other cases they may require you to enter into a formal 'building over a sewer' legal agreement before proceeding, which may be conditional on you incorporating special measures, for instance a specialist foundation design or a diversion of the drain. In some cases, the water authority may have the power to refuse permission for the building work altogether, but this is very rare.

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New legislation on sewers

New laws, which came into force in October 2011, have seen many private drains transfer to the ownership of the water authorities. This means that a drain crossing your property which was private may now be a public sewer. As a general principle the transfer applies to any drain which serves more than one property.

The advantage to a householder of the change is that the water authority will now be responsible for any repairs or maintenance to that drain. However, it may impose restrictions on you if you are planning building works.

In terms of the Building Regulations, nothing changes initially since the legal requirement in the regulations refers to drains which are 'shown on a map of sewers'. The newly transferred drains are not yet shown on the water authority map of sewers and so not subject to the regulations, though this may change gradually. We would still advise, however, that you contact the water authority before carrying out any work within 3m of a drain if it has transferred to their ownership.

For further information, visit the Water UK website.

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