Off-Mains Drainage Compliance
Is your septic tank or private drainage system compliant?
An off-mains drainage compliance check assesses your private sewage system, its condition and its discharge arrangements against the General Binding Rules that apply to small sewage discharges in England.
Boxall Ward inspects septic tanks, sewage treatment plants and associated drainage arrangements for homeowners, buyers, sellers, executors, trustees and others responsible for private drainage systems. The inspection is normally non-invasive and focuses on the accessible system and visible evidence at the property. CCTV or dye testing can be used where further investigation is appropriate.
Following the inspection, you receive a written report explaining the findings, any apparent compliance concerns and the practical next steps.
Information reviewed: September 2026 against current Environment Agency guidance for small sewage discharges in England.
What is an off-mains drainage compliance check?
An off-mains drainage compliance check is a specialist assessment of a property’s private sewage and drainage arrangements. Its purpose is to establish what system is installed, where the wastewater goes, whether there are visible defects or signs of failure, and whether the arrangements appear to meet the General Binding Rules that apply to the discharge.
You may also see this type of service described as a septic tank survey, septic tank compliance inspection, private drainage survey or homebuyer septic tank survey. At Boxall Ward, these terms describe the same core specialist inspection rather than completely separate services.
This is different from a general building survey. A conventional surveyor may note that a property has private drainage, but a specialist off-mains drainage inspection focuses specifically on the tank or treatment plant, the associated drainage arrangements and the system’s discharge.
Who needs an off-mains drainage compliance check?
Compliance checks are not only for people buying a house. The person responsible for the system – described by the Environment Agency as the operator – has ongoing responsibilities for the sewage discharge.
Homeowners
For reassurance about an existing septic tank, sewage treatment plant, drainage field or discharge arrangement.
Property sellers
To identify potential drainage or compliance problems before they delay a sale or become a point of renegotiation.
Homebuyers
To understand the system and any potential future costs before becoming responsible for it.
Executors & trustees
Where responsibility for a property includes responsibility for its private drainage arrangements.
Shared-system users
Where several properties use the same septic tank, treatment plant or drainage arrangement.
Property professionals
Where solicitors, conveyancers or estate agents need the physical drainage arrangements clarified during a transaction.
What does Boxall Ward check?
Every property is different, so the exact inspection depends on the type, age and accessibility of the drainage system. The inspection is primarily a surface-level visual assessment: we do not routinely excavate the site simply to carry out the compliance check.
Depending on the system and what can be accessed, the inspection may consider:
- The type of system installed – for example a septic tank or sewage treatment plant.
- The apparent size, layout and configuration of the system.
- Accessible tank chambers and their visible structural condition.
- Inlet and outlet arrangements.
- Baffles, dip pipes, compartments and other accessible components where applicable.
- The apparent route of the discharge from the system.
- The drainage field or infiltration arrangement where this can be identified.
- Signs of poor drainage, saturation, sewage odours or pollution.
- Visible evidence of leakage, damage or deterioration.
- Whether the system appears to be operating at an appropriate level.
- The relationship between the drainage arrangement and nearby watercourses or other relevant site features.
- Available information about the system’s age, installation, alterations, maintenance and approvals.
Where necessary, CCTV inspection may help trace buried pipework or establish the direction of a discharge. Dye testing can also be used where it is useful in establishing how part of the drainage system operates.
The purpose is not simply to look inside the tank
Compliance depends on the drainage arrangement as a whole. A tank may appear sound while the outlet, drainage field, discharge route or associated records reveal a separate problem.
Should a septic tank be emptied before a compliance check?
Boxall Ward strongly recommends that a septic tank is emptied, or de-sludged, where appropriate before inspection.
When a tank is full, wastewater and accumulated sludge can hide important parts of its structure. Emptying the tank can make it possible to see defects that might otherwise be concealed, including cracks, damaged brickwork, debris, failed internal divisions, damaged baffles or other structural concerns.
Whether emptying is required will depend on the system and circumstances. If tankering or any additional investigative work is needed, this can be discussed before it is arranged.
Environment Agency Rules
What are the General Binding Rules?
The General Binding Rules are legally binding requirements governing small sewage discharges in England. They set the conditions that qualifying septic tanks and small sewage treatment plants must meet in order to operate without an environmental permit.
The rules are not simply recommendations or voluntary guidelines. The requirements that apply to a particular property depend on factors including:
- Whether the system discharges to the ground or to surface water.
- The daily volume of sewage discharged.
- When the discharge started.
- The type of treatment system being used.
- The location of the discharge.
- Whether relevant planning and Building Regulations requirements apply.
- Whether the system is properly maintained and in good working order.
- Whether the discharge is causing pollution.
You can read the Environment Agency’s current guidance on small sewage discharges to ground and small sewage discharges to surface water on GOV.UK.
A compliance check is an assessment, not an Environment Agency approval
Boxall Ward assesses the accessible system and the information available at the time of inspection. Some aspects of compliance can depend on historical records, permissions or buried infrastructure that cannot be confirmed by visual inspection alone.
Discharge to ground or surface water: why the difference matters
One of the most important questions in a compliance inspection is where the treated wastewater actually goes.
| Discharge arrangement | Key point |
|---|---|
| Septic tank to ground | A septic tank may discharge to ground through a suitable drainage field or infiltration system where the applicable General Binding Rules are met. |
| Sewage treatment plant to ground | A suitable small sewage treatment plant may also discharge treated effluent to ground through an appropriate drainage field. |
| Septic tank directly to a river, stream or ditch | A septic tank must not discharge directly to surface water. A direct septic-tank discharge to a watercourse needs to be changed. |
| Sewage treatment plant to surface water | A suitable treatment plant can discharge treated effluent to qualifying surface water where all applicable requirements are met. |
Under the permit exemption provided by the General Binding Rules, the normal maximum small sewage discharge is 2 cubic metres per day to ground or 5 cubic metres per day to surface water. Systems above the applicable threshold require a different assessment and may require an environmental permit.
What about cesspools and cesspits?
A genuine cesspool is a sealed holding tank with no discharge to the environment. Because it does not make a small sewage discharge, the General Binding Rules do not apply to it in the same way as they apply to a septic tank or sewage treatment plant. It must nevertheless be properly contained, emptied and managed.
Why the age of the drainage system matters
The General Binding Rules that apply are partly determined by when the discharge started. This is one reason why an apparently simple question such as “Is my septic tank compliant?” does not always have a one-line answer.
Older existing discharges
Existing discharges in this category must meet the rules that apply to all qualifying small sewage discharges.
Post-2015 discharges
Additional rules can apply, including requirements relating to matters such as necessary planning and Building Regulations approvals.
New discharges
Further General Binding Rules apply to new discharges, including additional restrictions concerning shared outlets and the proximity of other exempt discharge points.
Replacing equipment does not automatically mean that every discharge becomes a completely new discharge for regulatory purposes. Equally, moving a discharge point, changing where it discharges or significantly changing its volume can affect which rules apply.
This is why the compliance check considers the history and configuration of the drainage arrangement, not simply the age printed on the tank.
A common misconception
A drainage system can appear to work and still not be compliant
No sewage smell, no overflowing tank and no waterlogged garden does not necessarily prove that a private drainage system meets every requirement that applies to it.
Compliance can depend on matters that are not obvious from day-to-day performance. The discharge arrangement may be unsuitable, the system may lack relevant approvals, part of the infrastructure may not meet the required standard, or the property’s circumstances may have changed since the system was installed.
Conversely, an ageing-looking system is not automatically non-compliant simply because it is old. The correct assessment depends on the system, discharge, history, condition and rules that apply to that particular property.
What will your written compliance report tell you?
After the inspection, Boxall Ward provides a written report setting out the findings. The purpose is to give you a clear, practical picture of the private drainage system rather than pages of technical information with no obvious conclusion.
Depending on the system and evidence available, the report can address:
- The type of private drainage system identified.
- The visible condition of accessible components.
- The apparent discharge arrangement.
- Relevant General Binding Rules considerations.
- Potential defects or compliance concerns.
- Anything that could not be established during the inspection.
- Recommended maintenance, further investigation or remedial works.
The conclusion is based on what can reasonably be established from the accessible system, the inspection and the supporting information available at the time.
Do you receive a septic tank compliance certificate?
No – there is no official Environment Agency septic tank compliance certificate.
Boxall Ward provides a written inspection report. This records the findings and gives an assessment of the drainage arrangement based on the accessible evidence.
Be cautious about treating the phrase “compliance certificate” as though it were an official document issued by the Environment Agency. At present, the report itself is the appropriate record of the specialist inspection.
What happens if your septic tank or drainage system is not compliant?
Finding a problem does not necessarily mean starting again from scratch. The right solution depends on what is wrong with the existing system.
In some cases the answer may be maintenance, repair or further investigation. In others, the property may need a new drainage field, alterations to the discharge arrangement, replacement of an old septic tank with a modern sewage treatment plant or connection to the public foul sewer.
This is an important advantage of using Boxall Ward for the initial compliance check: we do not simply identify a drainage problem and leave you to find somebody else to resolve it.
Repairs
Practical remedial work where an existing system can be retained.
Drainage fields
Assessment, replacement and installation of suitable infiltration arrangements.
Treatment plants
Replacement of unsuitable or failed septic arrangements with modern sewage treatment systems where appropriate.
Sewer connections
Connection to the public foul sewer where this is the appropriate solution.
Groundworks
The excavation and associated works required to deliver the drainage solution.
Environment Agency permits
Assistance with domestic permit requirements where a discharge cannot operate under the General Binding Rules.
Real Boxall Ward project
From a non-compliant septic system to a complete new drainage solution
At a property in Wadhurst, East Sussex, the existing septic system was found to be non-compliant. Boxall Ward assessed the situation and replaced it with a modern Matrix CLF1A IPS sewage treatment plant together with a new drainage field.
The complete project was taken from quotation to completion within two weeks, giving the customer a modern and reliable off-mains drainage system.
Buying or selling a property with a septic tank?
Private drainage often becomes particularly important during a property transaction because the buyer may be taking on responsibility for infrastructure that is largely underground and may have been installed many years ago.
A compliance check before exchange can help establish what system serves the property, where it discharges, whether there are obvious defects or regulatory concerns and whether significant expenditure may be required after purchase.
For sellers
Identifying a drainage issue early gives you the opportunity to understand it before a buyer’s solicitor or survey raises the problem late in the transaction. The General Binding Rules also require information about the sewage treatment system to be passed to the new operator when responsibility changes.
For buyers
A specialist inspection can reveal issues that are unlikely to be covered by a standard building survey. Where a problem is found, the report can help you understand the likely next steps before you become legally committed to the purchase.
For a fuller explanation, see what happens during a septic tank homebuyer survey.
Buying a property with a shared septic tank?
A shared drainage arrangement brings additional questions around access, maintenance and responsibility. A physical drainage survey can establish the system and its condition, although legal arrangements for ownership and cost sharing should also be checked by your solicitor or conveyancer.
See our guide: Who is responsible for a shared septic tank?
Clear pricing
How much does an off-mains drainage compliance check cost?
£375 + VAT
The compliance check includes the site inspection and written report described on this page. Where additional investigation, emptying, CCTV work, dye testing or remedial work is required beyond the normal inspection, this will depend on the property and can be discussed separately.
Areas covered
Boxall Ward carries out off-mains drainage work across Sussex and the wider South East, including areas of Surrey, Kent, Hampshire, Berkshire, the New Forest and surrounding rural areas.
If you are unsure whether your property is within our normal working area, call us on 01903 815377.
Off-mains drainage compliance FAQs
Is a compliance check the same as a septic tank survey?
At Boxall Ward, yes. Customers use several different names for the service, including septic tank survey, compliance inspection, private drainage survey and homebuyer septic tank survey. The core service is a specialist assessment of the private drainage system, its condition and its discharge arrangements.
How much does a Boxall Ward compliance check cost?
The price is £375 + VAT for the compliance check and written report. Any additional work required beyond the normal inspection depends on the property and can be discussed separately.
Does the septic tank need to be emptied before the inspection?
We strongly recommend emptying or de-sludging the tank where appropriate because this makes it easier to inspect the tank’s internal condition and identify structural defects that might otherwise be hidden.
Do you dig up the garden during a compliance check?
No. The compliance check is primarily a non-invasive surface-level visual inspection and we do not routinely break ground. CCTV or dye testing may be used where they are appropriate to the investigation.
Can a septic tank discharge directly into a ditch or stream?
No. A septic tank must not discharge directly to surface water. Depending on the property, the solution may involve a suitable drainage field, replacement with a sewage treatment plant or another compliant drainage arrangement.
Does a sewage treatment plant automatically comply with the General Binding Rules?
No. Installing a treatment plant does not automatically make every drainage arrangement compliant. The type of discharge, system condition, location, age, approvals, maintenance and other applicable rules can all matter.
Can a drainage system be working but still be non-compliant?
Yes. A system may appear to drain normally and show no obvious pollution while still having a regulatory or infrastructure issue. This is one of the reasons a specialist compliance assessment considers more than whether the toilets flush and the tank is not overflowing.
Will I receive a compliance certificate?
No official Environment Agency septic tank compliance certificate is issued. Boxall Ward provides a written report explaining the inspection findings and the apparent compliance position based on the evidence available.
What happens if my septic tank is found to be non-compliant?
We will explain the problem and the practical options. Boxall Ward can also carry out remedial works including repairs, drainage fields, sewage treatment plant installation, groundworks and public sewer connections where required.
Who is responsible for complying with the General Binding Rules?
The person responsible for the sewage treatment system is described as the operator. Depending on the property this may be the homeowner, several joint users of a shared system, a trustee, executor or another person who controls the system.
Should I have the septic tank checked before buying a house?
Yes, where a property relies on private drainage it is sensible to establish the system’s type, condition and discharge arrangements before exchange. A standard building survey will not normally provide the same specialist assessment.
What if my system cannot meet the General Binding Rules?
Some systems may need alterations or replacement. Where a qualifying discharge genuinely cannot meet the General Binding Rules, an Environment Agency permit may be required. Boxall Ward can assist with domestic permit matters where appropriate.
Need a clear answer?
Book an off-mains drainage compliance check
If you are unsure whether a septic tank, sewage treatment plant or private drainage system meets the current requirements, Boxall Ward can inspect the system and provide a written report explaining what we find.
Compliance check: £375 + VAT
Regulatory note: The General Binding Rules referenced on this page apply to small sewage discharges in England. Requirements can change and individual sites can require additional permissions or an environmental permit. For definitive regulatory guidance, refer to the Environment Agency information on GOV.UK.