If your property is not connected to the mains sewer, you are responsible for understanding and maintaining its private drainage system.

That sounds straightforward. In practice, many property owners do not know exactly what type of system they have, where it discharges or whether it meets the current General Binding Rules.

A septic tank or sewage treatment plant may have operated for many years without an obvious problem. That does not necessarily mean that it is correctly sized, in good condition or discharging in a compliant way.

A septic tank compliance inspection can provide a much clearer picture. Rather than looking only at the tank, it considers the private drainage system as a whole: how wastewater leaves the property, how it is treated, where the resulting effluent goes and whether repairs or upgrading work may be needed.

What Are the General Binding Rules for Private Drainage?

The General Binding Rules are environmental requirements governing small sewage discharges in England.

They apply to properties using private drainage systems such as:

• Septic tanks
• Small sewage treatment plants
• Drainage fields and septic tank soakaways
• Cesspools or cesspits
• Shared off-mains drainage systems

Where all the relevant General Binding Rules are met, a small sewage discharge can normally operate without an individual environmental permit. Where the rules cannot be met, the operator may need to alter the system, connect to the public foul sewer or apply for a permit.

The operator is generally the person responsible for the system. This may be the property owner, several owners sharing one system or, in some circumstances, a tenant whose agreement makes them responsible for it.

One of the most important requirements is that effluent from a septic tank must not discharge directly into surface water. This includes rivers, streams, ponds, lakes and watercourses. A septic tank should normally discharge into the ground through a correctly designed drainage field.

A small sewage treatment plant treats wastewater to a higher standard and may, in suitable circumstances, discharge to flowing surface water. However, that discharge must still meet the relevant rules and may require a permit in some locations or situations.

For a more detailed explanation, read our guide to the General Binding Rules and property sales or visit the official government guidance on septic tanks and sewage treatment plants.

Why Might You Need a Septic Tank Compliance Inspection?

You may have recently bought a property and inherited a private drainage system you know very little about. You may be preparing to sell, extending the house, increasing the number of occupants or experiencing smells, wet ground or drainage problems.

In other cases, nothing obvious has gone wrong. The owner simply wants to establish what is installed and whether there are any issues that should be dealt with before they become more serious.

An inspection may be particularly useful when:

• You do not know where the system discharges
• The septic tank or treatment plant is old
• There are no installation or servicing records
• The system has not been inspected for several years
• The property has been extended
• More people now use the property
• The tank needs emptying unusually frequently
• There are smells, slow drains or sewage backups
• The ground near the system is wet or waterlogged
• A ditch, stream or watercourse lies close to the property
• You are buying or selling the property
• A solicitor, surveyor or estate agent has raised questions about the drainage

The purpose is not to assume that something is wrong. It is to replace uncertainty with practical information.

Boxall Ward provides a dedicated off-mains drainage compliance service for property owners who need to understand the condition and apparent compliance of an existing system.

What Does an Off-Mains Drainage Inspection Check?

A proper inspection should look beyond the access cover and consider how the entire system operates.

The precise scope will depend on the property, the type of installation and how much of the system can be safely accessed. However, a septic tank compliance inspection will normally consider the following areas.

1. What Type of Private Drainage System Is Installed?

The first step is to identify what serves the property.

Although people often use the term “septic tank” for any private sewage system, the installation may actually be:

• A traditional septic tank
• A package sewage treatment plant
• A cesspool or cesspit
• A shared system serving several properties
• An older or modified system that requires further investigation

This distinction matters because each system works differently.

A septic tank separates solid waste from liquid effluent and normally relies on a drainage field for further treatment and dispersal into the ground.

A sewage treatment plant uses mechanical and biological processes to treat wastewater to a higher standard.

A cesspool is a sealed holding tank. It should not discharge effluent and must instead be emptied regularly.

Our guide to septic tanks and sewage treatment plants explains what the different systems can reveal during an inspection.

2. Where Is the Tank or Treatment Plant Located?

An inspection should establish the location of the principal components wherever possible.

This may include:

• The septic tank, treatment plant or cesspool
• Access covers
• Inlet and outlet pipes
• Inspection chambers
• Electrical equipment
• Alarms and control panels
• The drainage field or discharge route

This information can be surprisingly difficult to find at older rural properties, particularly where landscaping has changed or previous owners left no plans.

Knowing where the system is located makes future maintenance, emptying and repair work considerably easier.

3. What Condition Is the System In?

Visible and accessible components can be checked for signs of damage or deterioration.

Potential concerns may include:

• Cracks or structural damage
• Damaged or unsafe access covers
• Corrosion
• Displaced pipework
• Leaking joints
• Damaged internal components or baffles
• Unusually high or low liquid levels
• Evidence of groundwater entering the system
• Signs that effluent is escaping
• Worn or failed mechanical components
• Malfunctioning alarms or control equipment

Some defects are immediately apparent. Others may only become visible after the tank has been emptied or through further investigation.

Where a fault is identified, Boxall Ward can advise whether an appropriate off-mains drainage repair is possible or whether more extensive work is likely to be needed.

4. Where Does the System Discharge?

This is one of the most important questions in any septic tank compliance inspection.

A system may discharge:

• Into a drainage field
• Through another infiltration system
• Into a watercourse
• Into a ditch
• To an unknown location
• Through an arrangement that has been altered over time

A septic tank should not discharge directly to a river, stream, ditch, pond, lake or other surface water. Its effluent should normally pass into the ground through a suitable drainage field.

Where the discharge route cannot be confirmed, further investigation may be recommended. Simply knowing that a pipe leaves the tank is not enough; it is important to understand where that pipe goes.

5. Is the Drainage Field Showing Signs of Failure?

The drainage field is a critical part of a septic tank system.

It distributes liquid effluent through perforated underground pipes, allowing it to filter through the soil. This provides further treatment and enables the water to disperse safely.

A failing drainage field may cause:

• Wet or boggy ground
• Unusually lush vegetation
• Unpleasant smells
• Sewage appearing at ground level
• Slow drainage within the property
• Wastewater backing up towards the tank
• The tank filling again soon after emptying
• Pollution of nearby land or water

A drainage field can deteriorate through age, poor design, unsuitable ground, vehicle damage, root intrusion, excessive water use or a build-up of solids entering from the tank.

Read our detailed explanation of how a septic tank drainage field works and our guide to why the soakaway matters during a septic tank survey.

6. Is the System Suitable for the Property?

A private drainage system should be capable of handling the volume of wastewater produced by the people and activities it serves.

A system that was suitable when originally installed may no longer be adequate if:

• The house has been extended
• Extra bedrooms have been added
• The number of occupants has increased
• An outbuilding has been connected
• The property is now used as holiday accommodation
• A business operates from the site
• Several properties share the installation
• Water use has increased substantially

An undersized system can become overloaded, resulting in poor treatment, frequent emptying, unpleasant smells, drainage-field failure or pollution.

An inspection can identify whether the apparent capacity of the installation is consistent with the property’s current use and whether a more detailed assessment is advisable.

7. Has the System Been Properly Maintained?

The General Binding Rules require systems to be properly operated and maintained.

For a sewage treatment plant, this may include evidence of routine servicing, desludging and repairs by a competent person.

For a septic tank, maintenance includes regular emptying at an appropriate frequency and preventing excessive solids from entering the drainage field.

Useful records may include:

• Emptying receipts
• Servicing reports
• Installation documents
• Product information
• Repair invoices
• Planning or Building Control records
• Environmental permits
• Previous inspection or survey reports

A lack of paperwork does not automatically mean that a system is non-compliant, but it can make its history and condition harder to establish.

Regular sewage treatment plant servicing can help keep mechanical systems working efficiently and in line with the manufacturer’s requirements.

8. Is There Evidence of Pollution or Environmental Risk?

A private drainage system must not cause pollution.

Warning signs can include sewage odours, discoloured water, effluent on the ground, contaminated ditches or watercourses, or wastewater emerging beyond the intended drainage area.

The property’s surroundings also matter. The risk may be greater where the system lies close to:

• A river, stream or ditch
• A well, spring or borehole
• Groundwater used for drinking water
• A protected environmental site
• Neighbouring properties
• Land liable to flooding

The applicable rules can vary according to the discharge type, daily volume, location and whether it is classed as a new or existing discharge.

Does an Inspection Provide a Septic Tank Compliance Certificate?

There is no simple universal certificate that guarantees every private drainage system complies with every legal and environmental requirement.

An inspection can assess the accessible system, record its condition, establish the apparent discharge arrangement and identify visible concerns. It can also provide practical recommendations based on the evidence available at the time.

However, parts of an older system may be underground, inaccessible or undocumented. In some situations, additional investigation, drainage tracing, ground testing, environmental advice or permit enquiries may be necessary.

For that reason, owners should be cautious of anyone offering an instant guarantee of compliance without properly investigating the installation and discharge.

A clear inspection report is valuable because it explains what has been observed, what remains uncertain and what action may be appropriate.

What Happens If the Septic Tank Does Not Appear Compliant?

Discovering a potential problem does not necessarily mean that the entire system must immediately be replaced.

The appropriate solution depends on the cause.

Possible recommendations might include:

• Repairing damaged pipework or components
• Emptying and cleaning the system
• Servicing or repairing a treatment plant
• Investigating an unknown outlet
• Replacing a failed drainage field
• Redirecting a septic tank discharge to a suitable drainage field
• Upgrading from a septic tank to a sewage treatment plant
• Installing a larger system
• Applying for an environmental permit
• Connecting to the public foul sewer where this is reasonable

The advantage of identifying the issue through an inspection is that any subsequent work can be based on evidence rather than assumption.

Boxall Ward can provide the necessary groundworks for private drainage systems, repairs and replacement drainage fields, as well as the installation of domestic and commercial sewage treatment plants.

Do You Need a Different Survey When Buying a Property?

A compliance inspection can be useful for an existing owner who wants to understand the present system. However, someone purchasing a property will normally need a more detailed homebuyer survey.

A specialist survey can help establish:

• What type of system serves the property
• Its apparent condition and capacity
• The location and condition of the drainage field
• Where the system discharges
• Whether visible defects or compliance concerns exist
• Whether repairs, replacement or further investigation may be needed

Boxall Ward provides homebuyer septic tank surveys for rural and semi-rural properties across Sussex, Kent, Surrey, Hampshire and the wider South East.

Solicitors, conveyancers and estate agents can also read our guidance on septic tank surveys during property transactions.

Should You Wait Until There Is a Problem?

Usually, no.

Once sewage begins backing up, effluent appears at ground level or a pollution issue is reported, the situation becomes more urgent and potentially more expensive.

An earlier inspection gives you time to understand the system, consider the available options and plan any work properly.

It can also help when making decisions about:

• Extending or renovating a property
• Increasing occupancy
• Selling a house
• Purchasing a rural property
• Changing the use of a site
• Replacing an ageing tank
• Budgeting for future drainage work

Private drainage systems are much easier to manage when their condition and discharge arrangements are known.

Arrange a Septic Tank Compliance Inspection

If you are unsure what type of system serves your property, where it discharges or whether it appears to meet the current General Binding Rules, Boxall Ward can help.

We inspect septic tanks, sewage treatment plants, cesspools and associated private drainage systems across Sussex, Surrey, Kent, Hampshire, Berkshire, the New Forest and surrounding areas.

Where a problem is identified, we can provide practical advice and, where appropriate, carry out the repairs, groundworks, drainage-field work or system replacement needed to put it right.

Call 01903 815377, email enquiries@boxallward.co.uk or contact Boxall Ward to discuss your property and arrange an inspection.

Frequently Asked Questions