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Trusted drainage in London

Blocked drains announce themselves: gurgling, slow draining, smells, then overflow. Clearing is quick; the real value is finding out why it blocked — so it doesn't happen again next month.

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What we can help with

  • Blocked drains, toilets and sinks
  • Drain unblocking, clearance and cleaning
  • CCTV drain surveys
  • Drain repairs and lining
  • Gully and surface drainage

Popular drainage services

Also covered: Drain repairs and lining · Drain cleaning and descaling · Blocked toilets and sinks · Surface and gully drainage · French drains— describe the job in your request and we’ll route it correctly.

The law on drainage

Statutory basis

Drainage work in dwellings is covered by Part H ('Drainage and waste disposal') of the Building Regulations, with statutory guidance in Approved Document H covering foul water drainage, both above and below ground, pipe sizes, protection of pipes, manholes and inspection chambers. Separately, the right to connect to and the protection of public sewers is governed by the Water Industry Act 1991. Section 106 of that Act establishes the 'right to communicate with public sewers': owners or occupiers of premises are generally entitled to have their drains discharge into public sewers, subject to restrictions (e.g. no factory effluent, no direct connection to storm-overflow sewers, and separation of foul/surface water where required), and the sewerage undertaker may refuse permission if the drain does not meet the required standard.

Source — checked 21 July 2026

Who may legally do this work

There is no dedicated statutory register for drainage contractors distinct from the general plumbing position — anyone may legally carry out most domestic drainage work (e.g. clearing blockages, CCTV drain surveys, drain repairs) without a specific licence. However, building over or near a public sewer requires a formal build-over agreement with the relevant water and sewerage undertaker before work starts, regardless of who carries out the physical work — this is a consent requirement tied to the land/works, not a licensing requirement on the contractor.

Source — checked 21 July 2026

If you own and live in the property

  • Thames Water (the sewerage undertaker for almost all of Greater London) states: 'A build over agreement is a contract between you and your sewage provider, when you're building over, or near a sewer.' An application is required if building 'within 3 metres of a public sewer' or 'within 1 metre of the point where a pipe serving only your property crosses your boundary.' Critically, 'planning permission does not grant you permission to build over a sewer or drain' — the two consents are separate.

    Source — checked 21 July 2026

  • Consequences of not obtaining a build-over agreement, per Thames Water, include being unable to obtain a Building Regulations completion certificate, complications on a future property sale, potential legal action ('we could seek an injunction to remove the building and potentially recover damages'), and that 'liability for any damage caused to the sewers or drains during the construction lies with you' regardless of consent status.

    Source — checked 21 July 2026

  • Applications are classified by sewer diameter — Class 1 (internal diameter up to 175mm), Class 2 (176mm-350mm) and Class 3 (over 350mm) — with different fees (Class 1: £130; Class 2: £490; Class 3: £585+, per Thames Water's published figures) and different survey requirements. Thames Water also offers a free, instant self-certified build-over agreement for domestic sewers of 160mm diameter or less that pose 'little risk to the pipe.'

    Source — checked 21 July 2026

If you’re a landlord

  • No drainage-specific statutory duty distinct from a landlord's general repairing obligations was found in the sources checked. A landlord undertaking building work over or near a sewer at a rental property is subject to the same build-over agreement requirement as any other property owner.

    Source — checked 21 July 2026

Certificates & records

  • Build-over agreement

    Who must hold it:
    Whoever is carrying out building work within 3 metres of a public sewer or 1 metre of a private lateral drain crossing the property boundary
    Frequency:
    One-off, per project — obtained before construction starts

    The build-over agreement is issued by the sewerage undertaker (Thames Water for almost all of London) following a technical review (Thames Water states this takes place 'within 21 days' for the initial review) and, for larger sewers, a pre-construction CCTV survey.

    Source — checked 21 July 2026

Commonly misunderstood

  • Myth vs fact

    Myth: Homeowners who have obtained planning permission for an extension often assume they are also clear to build over a nearby sewer.

    Fact: Thames Water is explicit: 'Planning permission does not grant you permission to build over a sewer or drain.' A separate build-over agreement application must be made directly to the sewerage undertaker, and it can take substantially longer than the planning process for larger sewers (Thames Water cites 3-6 months for the largest Class 3 sewers).

    Source — checked 21 July 2026

Penalties for non-compliance

  • Thames Water states that 'retrospective agreements may not be approved if our pipework was not properly protected' and that building without an agreement can lead to 'issues selling your property later.' No specific fixed statutory fine figure for a build-over breach was found in the sources checked today; Thames Water's stated recourse is civil (injunction to remove the building and recovery of damages) rather than a named criminal penalty.

    Source — checked 21 July 2026

How to check who’s legally allowed to do this

There is no equivalent of the Gas Safe Register for drainage contractors generally. For build-over agreement compliance specifically, the relevant sewerage undertaker (Thames Water for almost all of London) is the authority to check with and to apply to directly, rather than checking a contractor's credentials.

thameswater.co.uk

Source — checked 21 July 2026

Medium confidence

Some detail in this section could not be independently confirmed against a primary source at the time of checking — treat exact figures and edge cases as indicative, not guaranteed, and confirm anything material before relying on it.

Could not establish a specific statutory fine figure for building over a public sewer without consent, beyond the civil remedies (injunction, damages) that Thames Water describes. Did not verify whether every part of Greater London is served by Thames Water specifically, versus a neighbouring undertaker at the fringes of the region.

Checked against the sources cited above on 21 July 2026. Rules and guidance change — always confirm anything material against the official source before acting on it.

How it works

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  2. 2

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  3. 3

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Pricing, honestly

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Areas we cover

London Heroes covers all 33 London boroughs around the clock. Choose yours for the local picture, including what your council requires from landlords.

Drainage questions, answered

Why does my drain keep blocking?
Recurring blockages have a cause — fat build-up, scale, intruding roots, or a displaced joint. A CCTV survey finds it in an hour. Clearing the same blockage quarterly costs more within a year than fixing the cause once.
What shouldn't go down the drain?
Fat and oil (they set like candle wax in cold pipes), wipes of any kind — including 'flushable' ones — cotton wool, and coffee grounds. London's sewer network is Victorian in places; it deserves gentler treatment.

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