FCA authorised · FRN 724952 0117 325 0027Quote & buy →
Civil and drainage engineers
Yes. If you design drainage, prepare flood risk assessments or survey drains and sewers for clients, you need professional indemnity insurance. Your work helps decide whether a scheme gets planning permission, whether a sewerage undertaker will adopt its sewers and whether new homes stay dry. When a design or assessment is wrong, the loss is redesign, delay and flood damage claims, and public liability is not designed to pay for negligent advice.
Part of: Engineers’ professional indemnity insurance
In short
Drainage consultants are judged on design and assessment: SuDS strategies, flood risk assessments, sewer adoption layouts, CCTV surveys and Building Regulations Part H drainage. In Wales, Schedule 3 to the Flood and Water Management Act 2010 has applied since 7 January 2019, so developments with a construction area of 100 square metres or more need SuDS approved by the SuDS approving body before construction starts. In England, Schedule 3 has not been brought into force and the Environment Agency says SuDS should follow Defra’s national standards. Sewers offered for adoption are built to a section 104 agreement. PI covers negligent design and advice, subject to the policy terms.
Last reviewed 5 October 2026 by the Apex professional indemnity team.
A drainage consultant’s product is a set of decisions: where surface water goes, how much storage a site needs, what a pipe can carry, how flood risk is presented to a planning authority and what a CCTV survey shows. Developers, contractors, sewerage undertakers and planning officers act on those decisions, usually long before a storm can test them.
Public liability (PL) insurance deals with accidents, such as a survey crawler that damages a drain or a manhole cover left unsecured. It is not designed for the claims that follow a drainage design, where nothing was damaged by accident but a planning application failed, sewers had to be relaid or an estate flooded because the system was undersized. Professional indemnity (PI) insurance covers your liability for those losses, and the cost of defending the claim, subject to the policy terms.
Drainage claims are also slow to surface. A design can sit untested for years until the rainfall it was meant to handle arrives, so how long your cover lasts matters as much as how much it pays.
The examples below are illustrative, not real claims. They show the allegations drainage consultants can face.
Each says the same thing: your design, assessment or survey fell short of what a competent drainage consultant would have produced, and someone lost money relying on it.
An expert reviewing a drainage claim will compare your work with the legislation, guidance and planning requirements that applied when you did it.
| Rule or guidance | What it says | Why it matters to your PI |
|---|---|---|
| Water Industry Act 1991, s.104 | A sewerage undertaker may agree with a developer that, if a sewer, lateral drain or sewage disposal works is built in accordance with the agreement, it will declare it vested in the undertaker on completion, at a specified date or when a future event happens. | Adoption depends on your design meeting the agreement’s terms. A rejected layout costs the developer time and money. |
| Environment Agency guidance on flood risk assessments (England) | An FRA is needed for development in Flood Zones 2 or 3, for sites of 1 hectare or more in Flood Zone 1 and for other sites at risk now or in future. It also sets out when a sustainable drainage strategy is needed, and warns that a planning authority may refuse an application without a satisfactory FRA. | An FRA that misses a source of flooding can cost a client its permission. |
| Defra national standards for sustainable drainage systems (2025) | Non-statutory standards for surface water drainage in England, including a hierarchy of runoff destinations and a management and maintenance plan to be provided by the designer. | The Environment Agency says SuDS should be designed in accordance with them, so they are the yardstick for your strategy. |
| Approved Document H, 2015 edition (England) | Foul water goes to a public sewer where reasonably practicable, then a private sewer connecting to one, then a treatment system, then a cesspool. Rainwater goes to a soakaway or other infiltration first, then a watercourse, then a sewer. Requirement H4 controls building over mapped sewers. | Building control checks your drainage design against these priorities. |
| Defective Premises Act 1972, s.1, with Limitation Act 1980, s.4B | Anyone taking on work in connection with providing a dwelling must do it in a professional manner so the dwelling is fit for habitation. Claims can be brought up to 15 years after the dwelling is completed, or 30 years where the right of action arose before 28 June 2022. | Drainage design for new homes can produce claims long after handover. |
Surface water drainage is regulated differently either side of the border, and the difference changes your exposure.
In Wales, Schedule 3 to the Flood and Water Management Act 2010 has been in force since 7 January 2019. The Welsh Government’s statutory guidance says new developments with a construction area of 100 square metres or more must have SuDS designed and built to the Welsh Ministers’ statutory standards and approved by the local authority, acting as SuDS approving body (SAB), before construction begins. That includes enabling works such as site clearance, level changes and cut and fill. The Act requires SABs to adopt drainage systems serving multiple properties, and the right to connect surface water to a public sewer depends on SAB approval.
In England, Schedule 3 has not been brought into force; legislation.gov.uk records its commencement for Wales only. There is no SAB. Surface water is dealt with through planning, with Defra’s non-statutory national standards as the design benchmark.
For your PI, that means:
| Usually covered by PI | Often excluded or limited | Needs a different policy |
|---|---|---|
| Negligent drainage strategies, SuDS and attenuation design | Fitness for purpose terms and promises that a site will not flood | Damage caused by your CCTV crew or equipment on site (public liability) |
| Errors in flood risk assessments and hydraulic modelling | Pollution and contamination claims, under some wordings | Injury to your own staff in chambers and confined spaces (employers’ liability) |
| Adoption layouts that fail technical approval because of your error | Jetting, lining, repairs and other contracting work, unless declared | Survey crawlers and cameras lost or damaged (equipment cover) |
| Misreported CCTV surveys and condition reports | Liquidated damages for delay, unless they flow from a covered negligent act | Pollution caused by your own site activities (public liability or environmental cover) |
| Defence costs and expert evidence | Claims or circumstances you knew about before the policy started | Loss of survey footage or client data in a cyber attack (cyber insurance) |
Cover depends on the insurer accepting the risk and on the wording. Check that the business description names every service you offer: a policy for “civil engineering design” may not obviously include CCTV surveys or flood risk assessments.
No law sets a PI limit for drainage consultants. Developers, contractors, housing associations and public sector frameworks set it in appointments, and funders and purchasers often ask for collateral warranties. Check the figure, whether it applies to each and every claim or in the aggregate, and whether pollution claims carry a lower limit in your wording. Before signing a warranty, read collateral warranties and PI.
Then think about time. PI is claims-made, so the policy in force when a claim is made is the one that pays, not the one you held when you designed the scheme. Housing drainage can attract Defective Premises Act claims for up to 15 years after completion, and appointments commonly require cover to be maintained for a set period after completion. Keep cover continuous, keep calculations, test results and survey footage, and arrange run-off if you retire or sell; see run-off cover explained and the Building Safety Act and PI.
A complete proposal gets better terms than a bare one, and a broker can only present what you tell us. Have these ready:
Speak to a broker
PI for drainage consultants, placed by a named broker
Start the online proposal and save it as you go, or leave your number and a named broker will call you back, usually the same working day.
Apex Insurance Brokers is an independent insurance broker based in Bristol, established in 2009 and authorised and regulated by the Financial Conduct Authority. We are not tied to one insurer: we work with over 30 markets, including Lloyd’s syndicates through wholesale brokers, and every client has a named broker who handles the placement, mid-term changes, certificates for clients and the renewal.
Yes. Drainage strategies, flood risk assessments, adoption designs and CCTV surveys are professional advice that developers and owners rely on. When they are wrong, the loss is redesign, delay or flood damage claims, which public liability is not designed to cover. PI covers your liability for negligent design and advice, subject to the policy terms.
No law requires drainage consultants to hold PI. It is required in practice: developers, contractors, housing associations and public sector frameworks set minimum limits in their appointments, and funders and purchasers often ask for collateral warranties that your PI must stand behind. Check each requirement before you sign.
A refusal is not a claim in itself. If your client later alleges your FRA was negligent and claims the cost of new modelling, redesign or delay, PI is designed to respond, subject to the policy terms. The Environment Agency warns that applications can be refused without a satisfactory FRA, so record the data and assumptions you used.
Your PI should describe the work, and your insurer should know you make SAB applications. In Wales, Schedule 3 to the Flood and Water Management Act 2010 requires SuDS for developments with a construction area of 100 square metres or more, approved by the SuDS approving body before construction starts, including enabling works such as site clearance.
You may be, if the refusal follows from a design error, such as a layout that does not meet the standards in the section 104 agreement. The developer could claim relaying costs and delay, and PI may respond, subject to the policy terms. Keep records of technical approval and of any changes others made on site.
Longer than many consultants expect. For work on new homes, the Defective Premises Act 1972 can apply, and claims under it can be brought up to 15 years after completion. Commercial clients may sue in contract or in negligence. Because PI is claims-made, keep cover in force and arrange run-off when you stop trading.
Apex arranges professional indemnity insurance for drainage consultants across the UK. Tell us about your work and we’ll find cover that fits. Or call 0117 325 0027.
Start your PI proposal Call 0117 325 0027Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Registered in England and Wales, company number 07014570. This page is general information, not advice on your individual circumstances. Cover is always subject to the insurer’s acceptance and the policy terms, and this page does not guarantee that cover will be available or on what terms.
