Guide
Who owns the drain on a commercial site, you or the water company?
Updated
On a commercial site the ownership question has two layers that a domestic property does not: the statutory split between private pipework and the public network, and then whatever the lease says about who maintains what inside the demise. Both need answering before anyone is instructed.
Layer one: private pipework or public network
Private sewers and lateral drains that were connected to the public sewer transferred to the water and sewerage companies from 1 October 2011. Thames Water puts it plainly for its region: "After a change in the law in 2011, we became responsible for private sewers/drains from 1 October 2011", and "You're still responsible for the sections of pipe between your property/building and the transferred private sewer or lateral drain" (thameswater.co.uk). The transfer was made under the Water Industry (Schemes for Adoption of Private Sewers) Regulations 2011 (legislation.gov.uk). Your own water and sewerage company publishes its own version for its area, and that is the one to check for your site.
Where commercial sites differ
- Large sites can be one curtilage. An industrial estate or retail park held and managed as a single site may have extensive pipework that never transferred, because it did not cross a boundary into another ownership before reaching the sewer. Big private networks are normal on commercial land.
- Site-specific assets are almost always yours. Pump stations, interceptors, grease management, attenuation tanks, yard drainage and process drainage serve your operation and sit inside your site. They are maintained by you regardless of what happened in 2011.
- Not everything was in scope. The transfer applied to private sewers and lateral drains connected to the public sewer; pipework laid later, and systems that do not connect to a public sewer at all, were not caught by it.
- Surface water can have a different owner from foul. Two systems, sometimes two answers. Establish which one is blocked before you decide who pays.
Layer two: what the lease says
Even where the pipe is unambiguously private, the lease decides whether the bill lands with the landlord, the tenant or the service charge. Full repairing and insuring leases commonly push drainage maintenance to the tenant inside the demise, with shared runs recovered through the service charge. Read the demise plan and the repair clause before you instruct anyone, because a tenant who pays for a landlord's shared run rarely gets it back afterwards.
The order to work through
- Establish which system and which chamber. Foul or surface water, inside the demise or outside it, upstream or downstream of the last chamber on your land.
- Check the statutory position for your area with your water and sewerage company. Where the blockage sits in a public sewer or a transferred lateral drain, that is their work.
- Then check the lease. Private pipework, private bill, but not necessarily your bill.
- Only then instruct. A CCTV survey with a plan is what turns this from an argument into a document, which is why it is the first spend on any recurring problem.
Keeping an up-to-date drainage plan of the site is the cheapest insurance in this whole area. It settles ownership arguments, shortens every future call-out, and is the thing a new contractor asks for first. If nobody has one, ask for it as a deliverable the next time a camera goes down the system.