Repairs: drainage

Key considerations

The requirements for modern drainage systems are contained in Building Regulations Approved Document H (AD H) – but this only deals with new work. The Regulations now include advice for grey water recycling and 'reclaimed water systems' and for underground water storage (AD H2).

The Regulations are well set out, and are not covered in depth here, suffice it to say that AD H covers:

  • sanitary pipework;
  • foul drainage;
  • adoption of sewers and connection to public sewers;
  • waste water treatment systems and cesspools and their maintenance;
  • rainwater drainage (touched on above under gutters and roofs);
  • surface water drainage generally;
  • storage of solid waste; and
  • water recycling.

The situation becomes a little more complicated, however, when repairing existing buildings or extending or adding to existing structures and combining new and old systems. This is touched on in Appendix H1-B of AD H.

Note: Although the Building Regulations do not have specific requirements relating to maintenance and repair of drains and sewers, local authorities or the statutory authority (statutory undertaker) providing sewerage services have powers to ensure that appropriate maintenance is carried out and that repairs or alterations are properly executed. This includes the power under section 48 of the Public Health Act 1936 for the local authority to test drains or sewers if it suspects these are causing a health hazard.

So, although the Building Regulations do not necessarily apply directly to repairs and alterations of existing drain systems, it is sensible to carry out the works in accordance with Approved Document H1. (The Regulations apply as soon as you are carrying out works that constitute a 'building operation' as defined in the Building Act.) Upgrading substantial older drainpipe runs to modern performance standards, however, can be nigh on impossible, so consider an appropriate standard to assess these problems.

'Out of sight is out of mind' is not a good motto when it comes to underground drainage. Take the opposite view, and ensure that the drainage system is thoroughly checked before you plan building or repair works. Drains may not even be where you think they are!

Sewers are not always where you think they are

It is not unheard of for building works to be suspended while an application is made for a sewer diversion. You may even need to rethink the position of an extension or a main structural wall to move it away from a sewer line that was only discovered once works have begun.

Sometimes even plotting the position of the drain between 2 chambers is not enough, and the supposed straight line between the 2 chamber positions may not exist, despite what the Building Regulations and best practice would normally dictate!

If you do not locate the actual position of drain runs you may end up with a considerable extra burden on cost and time once works have started. Even if you obtain drainage plans from the statutory authority (which it normally has to do this free of charge), they may only be indicative rather than give specific drain positions.

Note: A Building Over Agreement may be necessary, depending on the size and location of the drains. This may only be possible at the discretion of the local authority (which sometimes acts as agent on behalf of the statutory sewerage authority) or you may need to apply to the statutory services provider. Permission is not guaranteed.

Depending on the policy of the sewerage provider this could be a very expensive operation. The author recently encountered one sewerage authority that charged in the region of £10,000 for any sewer diversion! Your client will not thank you if charges such as this have not been pre-considered.

The basics should serve as a useful aide memoire to drainage issues when you are out on a site inspection.