Selling a House with a Septic Tank

Around one million properties in England are not connected to the public sewer network and instead rely on private drainage systems such as septic tanks, sewage treatment plants, or cesspools. If you are selling one of these properties, you need to understand what you are required to disclose, whether your system complies with current regulations, and how it might affect your sale.

This guide covers everything a seller needs to know about selling a house with a septic tank or other private drainage system in England and Wales. It explains the regulatory changes that took effect in January 2020, what your disclosure obligations are, and how to deal with buyer concerns during the conveyancing process.

Septic tank, treatment plant, or cesspool: know your system

Before you can answer questions on the TA6 Property Information Form or respond to buyer enquiries, you need to know exactly what type of private drainage system your property uses. The three main types work quite differently:

If you are unsure what type of system you have, check any documentation from when you purchased the property, look for an Environment Agency permit or exemption, or arrange an inspection by a drainage specialist. Your solicitor will need accurate information to complete the property information form.

The general binding rules: what changed in 2020

On 1 January 2020, the Environment Agency introduced general binding rules for small sewage discharges in England, replacing the previous system of individual permits for most domestic systems. These rules were introduced under the Environmental Permitting (England and Wales) Regulations 2016 and represent the most significant regulatory change for septic tank owners in recent years.

The general binding rules apply to septic tanks and small sewage treatment plants that have a maximum daily discharge of two cubic metres (for septic tanks) or five cubic metres (for treatment plants). Under the rules:

• Septic tanks must not discharge to a watercourse. If your septic tank currently discharges into a stream, river, ditch, or any other surface water, this is no longer permitted. You must either replace the tank with a sewage treatment plant, install a drainage field, or connect to the mains sewer.
• Discharge must go to a drainage field. Septic tanks must discharge their effluent to a drainage field (also called a soakaway), where it percolates through the soil for natural treatment before reaching the water table.
• No pollution. The system must not cause pollution of surface water or groundwater. If your system is causing visible pollution, odour nuisance, or contamination, you are in breach of the rules regardless of the discharge method.
• Regular maintenance. You must maintain your system in good working order and have it desludged regularly by a registered waste carrier.
• Siting requirements. New drainage fields must not be within 50 metres of a drinking water supply point (such as a well or borehole) or within a groundwater source protection zone 1 (SPZ1).

If your system previously held an Environment Agency permit and it meets the general binding rules, that permit was automatically cancelled on 1 January 2020. If your system does not meet the rules — for example, because it discharges to a watercourse — you need to take action to bring it into compliance.

When you must upgrade before selling

There is no specific legal requirement to upgrade your septic tank before the property changes hands. However, there are situations where an upgrade is effectively unavoidable:

• Your septic tank discharges to a watercourse. This has been illegal since 1 January 2020. If your system discharges into a stream, river, or ditch, you are operating in breach of the general binding rules. A buyer's solicitor will identify this through the conveyancing enquiries process, and most buyers will insist on an upgrade before completion or a significant price reduction to cover the cost.
• The system is causing pollution. If there is evidence of sewage pollution — such as standing effluent, contaminated watercourses, or odour complaints — the Environment Agency can take enforcement action against the property owner. A pollution incident is a material fact that must be disclosed on the TA6 form.
• The drainage field has failed. If the soakaway is waterlogged, has standing water on the surface, or is no longer absorbing effluent effectively, the system is not compliant. A failed drainage field may need to be replaced or relocated, which can be a significant cost.
• The buyer's lender requires it. Some mortgage lenders carry out environmental risk assessments and may impose conditions relating to the drainage system before approving the loan. If the lender identifies a non-compliant system, they may require evidence of an upgrade before releasing funds.

Where an upgrade is needed, the cost is typically negotiated between seller and buyer as part of the sale. Options include the seller carrying out the work before completion, agreeing a price reduction, or placing funds in escrow to cover the upgrade after completion.

TA6 disclosure requirements

Section 7 of the TA6 Property Information Form deals with drainage and asks specific questions about how the property's sewage is handled. As a seller, you must answer these questions honestly and completely. The key questions relevant to septic tank owners include:

• Whether the property is connected to the mains sewer or uses a private drainage system
• The type of private system (septic tank, treatment plant, or cesspool)
• Where the system discharges to (drainage field, watercourse, or sealed)
• Whether the system has an Environment Agency permit or is covered by the general binding rules
• Whether the system is shared with neighbouring properties
• Whether there have been any problems with the system, such as blockages, overflows, or pollution incidents

You should also provide supporting documentation alongside the TA6, including copies of any Environment Agency permits (even if cancelled), desludging receipts, maintenance records, installation certificates, and details of the drainage field location. The more comprehensive your documentation, the fewer additional enquiries the buyer's solicitor will need to raise.

Drainage searches and what they reveal

The buyer's solicitor will order a drainage search (CON29DW) as part of the standard conveyancing searches. This search is conducted with the local water company and provides information about mains drainage connections, public sewer locations, and water supply.

For properties with a septic tank, the drainage search will typically confirm that the property is not connected to the public sewer. This finding is significant because it:

• Alerts the buyer's solicitor to investigate the private drainage arrangements in detail
• Triggers additional enquiries about the system type, compliance status, and maintenance history
• May prompt the buyer's solicitor to recommend a specialist drainage survey before exchange of contracts
• Will be flagged in the environmental search results if there are known contamination or pollution risks in the area

The drainage search itself does not provide information about your septic tank's condition or compliance. That information comes from your TA6 answers, the documentation you provide, and any specialist surveys the buyer commissions.

Surveys and inspections

Buyers purchasing a property with a septic tank may arrange additional inspections beyond the standard homebuyer survey. As a seller, you should be prepared for:

• Septic tank survey. A specialist drainage contractor can inspect the tank, check its structural condition, assess the drainage field, and confirm whether the system is operating correctly. This typically costs £200 to £500 and provides a detailed report on the system's condition and any recommended work.
• Percolation test. If the drainage field's effectiveness is in question, a percolation test measures how quickly water drains through the soil. The results determine whether the existing soakaway is suitable or needs to be replaced. British Standard BS 6297 sets out the requirements for drainage field design and percolation testing.
• Environmental assessment. In some cases, the buyer's lender or solicitor may require an environmental assessment to check for contamination risks associated with the private drainage system, particularly if the property is near a watercourse or in an environmentally sensitive area.

Proactively commissioning a septic tank survey before listing your property can be a smart move. If the survey confirms the system is compliant and in good condition, it provides reassurance to buyers. If it identifies issues, you have time to address them before they become a problem during the sale.

Upgrade costs and options

If your septic tank does not comply with the general binding rules, you have several options for bringing it into compliance. The costs vary significantly depending on the work required:

Installation timelines vary from a few days for a straightforward treatment plant replacement to several weeks where planning permission, Environment Agency consultation, or complex groundwork is involved. If you are planning to upgrade before selling, factor in at least six to eight weeks from obtaining quotes to completing the installation.

Soakaway and drainage field requirements

The drainage field (soakaway) is a critical component of any septic tank system. It is where the liquid effluent from the tank percolates through the soil for natural treatment. Under the general binding rules, the drainage field must meet specific requirements:

• It must be at least 10 metres from any watercourse, 50 metres from a water supply point (well, borehole, or spring), and 15 metres from any building
• It must not be in a groundwater source protection zone 1 (SPZ1)
• The soil must be suitable — a percolation test to BS 6297 must confirm that water drains at an acceptable rate (neither too fast nor too slow)
• It must not be covered by hard surfaces, driven over by vehicles, or located where the ground becomes waterlogged
• It must be adequately sized for the volume of effluent the tank produces

Buyers' solicitors frequently ask about the drainage field location and condition. If you can provide a plan showing where the drainage field is situated relative to the property, watercourses, and boundaries, this answers several common enquiries in one go.

Desludging records and maintenance history

One of the most common requests from buyers' solicitors is for evidence of regular maintenance. Under the general binding rules, you are required to maintain your system and have it desludged by a registered waste carrier at appropriate intervals.

You should gather and provide:

• Desludging receipts covering at least the last three years, showing the date of each emptying and the name of the waste carrier
• Waste carrier registration details for the company that empties your tank (they must be registered with the Environment Agency)
• Service records for any mechanical components, particularly if you have a sewage treatment plant with pumps, aerators, or electronic controls
• Installation documentation including the manufacturer, model, capacity, and installation date of the system
• Building regulations sign-off if the system was installed or replaced after 2015, confirming it was installed to the required standard

Missing records do not prevent a sale, but they make the process slower. If you cannot locate your desludging receipts, contact your waste carrier — most companies keep records and can provide duplicate receipts. If you have no records at all, consider commissioning a professional inspection before listing, which can confirm the current condition and establish a baseline.

Shared septic tanks and drainage systems

Some properties share a septic tank or drainage system with one or more neighbouring properties. Shared systems add complexity to the sale because the buyer's solicitor will want to understand:

• Who owns the system and the land it sits on
• Whether there is a formal legal agreement governing maintenance responsibilities and cost sharing
• Whether there are rights of access for maintenance and emptying
• Who is responsible for compliance with the general binding rules
• Whether the other property owners are contributing to maintenance costs

If you share a system, you must disclose this on the TA6 form. If there is a formal maintenance agreement, provide a copy to your solicitor. If there is no formal agreement and the arrangement is informal, your solicitor may recommend putting an agreement in place before the sale, as buyers' solicitors are likely to raise this as a concern. Shared drainage arrangements can also affect the environmental search results, so it is worth flagging these early.

How to handle buyer concerns

Buyers who are unfamiliar with septic tanks can be apprehensive. The most effective way to manage buyer concerns is to provide clear, comprehensive information from the outset. Here is how to address the most common worries:

1. Provide full documentation upfront. Include your system type, age, capacity, permit or general binding rules status, desludging records, and a plan showing the tank and drainage field locations. This demonstrates that the system is properly managed and compliant.
2. Confirm compliance with the general binding rules. If your system discharges to a drainage field and is regularly maintained, state this clearly in your TA6 answers and provide supporting evidence.
3. Offer a specialist survey. If buyers are concerned about the system's condition, offering to share the cost of an independent drainage survey can build confidence and prevent the issue from stalling the sale.
4. Explain the running costs. Annual desludging typically costs £150 to £300 per visit, which is comparable to or less than annual mains sewerage charges. This context can help buyers who are concerned about ongoing expenses.
5. Address non-compliance honestly. If your system needs upgrading, being upfront about the issue and providing quotes for the work is more effective than trying to minimise the problem. Buyers appreciate transparency, and it avoids the issue becoming a deal-breaker later in the process.

Environment Agency permits and registrations

The permit position for domestic septic tanks in England has changed significantly. Before January 2020, small domestic discharges often required an individual Environmental Permit from the Environment Agency, or were covered by an exemption. Since the introduction of the general binding rules, the position is as follows:

• Systems that meet the general binding rules no longer need an individual permit. If you previously held one, it was automatically cancelled.
• Larger systems with a daily discharge exceeding two cubic metres (septic tanks) or five cubic metres (treatment plants) still require an individual permit from the Environment Agency.
• Discharges near sensitive areas such as Sites of Special Scientific Interest (SSSIs), Special Areas of Conservation, or groundwater source protection zone 1 may still require an individual permit regardless of size.
• New installations of septic tanks or treatment plants do not need a permit if they comply with the general binding rules, but they do need building regulations approval from the local authority.

When selling, you should provide any permit documentation you hold, even if the permit has been cancelled. This helps establish the history of the system and demonstrates that it was previously registered with the Environment Agency. If you are unsure about your permit status, you can check with the Environment Agency directly or search the public register of environmental permits.

Seller's checklist for properties with a septic tank

Use this checklist alongside your general documents needed to sell to make sure you have covered everything specific to your private drainage system:

1. Identify your system type (septic tank, treatment plant, or cesspool) and confirm its location on the property
2. Check whether your system complies with the general binding rules — in particular, confirm it does not discharge to a watercourse
3. Gather desludging receipts for at least the last three years
4. Locate any Environment Agency permits, exemptions, or correspondence
5. Find installation documentation, including the system manufacturer, model, and capacity
6. If the system is shared, locate any maintenance agreements and confirm the cost-sharing arrangements
7. Complete Section 7 of the TA6 form accurately and attach supporting documentation
8. Consider commissioning a septic tank survey before listing to identify and address any issues proactively
9. If the system is non-compliant, obtain at least two quotes for upgrade work so you can negotiate knowledgeably with the buyer
10. Prepare a plan or sketch showing the location of the tank, drainage field, and any watercourses on or near your property

Sources

• Environment Agency — General binding rules: small sewage discharge to the ground, GOV.UK
• Environment Agency — General binding rules: small sewage discharge to a surface water, GOV.UK
• DEFRA — Septic tanks and treatment plants: permits and general binding rules, GOV.UK
• Environmental Permitting (England and Wales) Regulations 2016 — legislation.gov.uk
• British Standard BS 6297:2007+A1:2008 — Code of practice for the design and installation of drainage fields for use in wastewater treatment
• Building Regulations 2010 (Part H: Drainage and waste disposal) — legislation.gov.uk
• Law Society — TA6 Property Information Form, 4th edition
• Environment Agency — Public register of environmental permits
• UK Finance Lenders' Handbook — ukfinance.org.uk

Frequently asked questions