Where your responsibility ends
You are responsible for the private drainage that serves your property up to the point where it connects to the public sewer, which is normally at or near the boundary. Scottish Water is responsible for the public sewer beyond that point, including shared sewers that were transferred into public ownership.
Where several properties share a private run before it reaches the sewer, that shared length is usually a common responsibility between the owners it serves, with the split set out in the title deeds or, in a tenement, in the tenement management scheme. This is the single most common source of disagreement between neighbours over drainage costs.
Building standards and warrants
New drainage, altered drainage and drainage affected by an extension fall under the building standards system administered by the local authority. Most such work needs a building warrant, and the completion certificate depends on the drainage being installed and tested to the technical handbook standards, which cover gradients, materials, access provision, ventilation and testing.
Like for like repair of an existing drain does not need a warrant. Replacing a failed section of pipe with an equivalent one is maintenance. Rerouting a run, adding a new connection or building over a drain is a different matter and should be discussed with building standards before the work rather than after.
Building over or near a public sewer
If you intend to build over or within a set distance of a public sewer, you will normally need a build over agreement with Scottish Water. They will want to know the position and depth of the sewer, the design of the proposed structure, and how future access for maintenance will be preserved. That is why a traced drainage plan is the practical first step for any extension where a sewer might be in the way.
Doing the work without agreement is a genuine risk. If the sewer later needs attention, the cost of getting to it through your new structure can fall to you.
Septic tanks, treatment plants and SEPA
- Any discharge to the ground via a soakaway or to a watercourse requires authorisation from SEPA.
- Small domestic discharges are usually covered by a general binding rule rather than a full licence, but the system must still be properly designed, sited and maintained.
- Registration is normally needed where a discharge is to a watercourse, and it is transferred when the property is sold.
- Tanks must be desludged by an authorised contractor and the waste taken to a licensed facility, with a record kept.
- New systems must meet current standards, which are stricter than those applied to systems installed decades ago.
Surface water and flooding rules
New development generally has to manage surface water sustainably rather than simply piping it to the nearest sewer, which is why soakaways, permeable paving and attenuation are now standard in new build. Adding significant new hard standing to an existing property can trigger the same considerations, particularly where run off would otherwise reach a neighbour or the highway.
Connecting a downpipe to a foul drain where a surface water system exists is not permitted, and it is a frequent cause of properties flooding during heavy rain because the foul run was never sized for storm flow.
Misconnections and pollution
A misconnection is a foul appliance plumbed into the surface water system, which then discharges untreated to a burn or river. Washing machines and downstairs toilets fitted during a conversion are the usual offenders. They are unlawful, they are a genuine pollution source, and they are found routinely on CCTV surveys.
Where we find one we record it with footage and tell you plainly what is connected where. Correcting it is usually a small piece of work compared to the consequences of leaving it.
Where people most often get caught out
The three recurring ones are building an extension over a run without checking what is underneath, connecting a new bathroom or utility into whichever pipe was nearest during a conversion, and assuming a shared drain is somebody else's responsibility because it is beyond the fence.
All three are cheap to avoid and expensive to unpick. A traced plan before design work, a proper look at what is being connected to during any alteration, and a read of the title deeds before a dispute begins will deal with almost all of them. Where you are unsure, building standards will usually give a straight answer to a straight question before the work starts.
Questions we get asked
Do I need a warrant to repair a drain?
Not for like for like repair. Altering, rerouting or adding drainage normally does require a building warrant.
Who owns a shared drain between two houses?
Usually the owners it serves, jointly, unless it has been transferred to Scottish Water. The title deeds are the starting point.
Can I build an extension over a drain?
Often yes, with the right design and, where a public sewer is involved, a build over agreement. It has to be planned, not discovered.
Does SEPA need to know about my septic tank?
Yes. Discharges to ground or water require authorisation, and registration transfers with the property when it is sold.