You can sell a house with a septic tank, but in England you must tell the buyer in writing that a sewage discharge is in place and give them details of the system, and a septic tank that discharges directly into a river or stream doesn’t meet the rules and needs replacing or upgrading. Who pays for that is something to agree with your buyer as part of the sale.
This guide explains the rules in England first, then how Wales, Scotland and Northern Ireland differ.
What are the general binding rules?
In England, the general binding rules are the Environment Agency’s rules for small sewage discharges from septic tanks and small sewage treatment plants. If your system meets them, you don’t need a permit. If your property is connected to the mains sewer, none of this applies to you.
GOV.UK says you are responsible for the system, known as the “operator”, if you own the property it serves, share it with others, or have a tenancy agreement that makes you responsible. Key rules include:
- Volume limits. You can discharge 2 cubic metres or less a day to the ground, or 5 cubic metres or less a day to surface water.
- Emptying. You must have the sludge removed before it goes beyond the maximum capacity, at least once a year or in line with the manufacturer’s instructions.
- Condition. You must have the system repaired or replaced if it is not in good working order.
Which rules apply also depends on when the discharge started. GOV.UK sets out different requirements for discharges that began before 1 January 2015, between 1 January 2015 and 1 October 2023, and on or after 2 October 2023.
What was the 1 January 2020 rule?
Under the general binding rules, a septic tank should not discharge directly to surface water such as a river or stream. GOV.UK says you must use a small sewage treatment plant if you are discharging to a watercourse, because it treats sewage to a higher standard than a septic tank.
When this rule was introduced, GOV.UK’s guidance tied it to property sales and to 1 January 2020. It said that where properties with septic tanks discharging directly to surface water were sold before that date, responsibility for replacing or upgrading the system should be agreed between buyer and seller as a condition of sale.
That date has passed, and the current guidance is plain. If your septic tank discharges directly to a watercourse, you must, as soon as possible, connect to a public foul sewer, replace the tank with a small sewage treatment plant, or install a drainage field, and you must have plans in place to do the work within a reasonable timescale, usually 12 months. It also still says that when a property is sold, buyer and seller should agree who will be responsible for the work, as a condition of sale.
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What must you tell a buyer?
GOV.UK says that if you sell your property in England, you must tell the new operator in writing that a sewage discharge is in place. You need to include a description of the system, where its main parts and discharge point are, its maintenance history, and any manuals.
Your solicitor will also ask you to complete the Law Society’s Property Information Form (TA6). In the 6th edition, questions 11.5 to 11.7 ask:
- whether the property is connected to mains foul and surface water drainage
- whether it has a septic tank, a sewage treatment plant or a cesspool
- when the discharge began, when the system was installed, and when it was last replaced or upgraded
- when a treatment plant was last serviced, or a cesspool last emptied
- whether the system discharges to the ground or to surface water, and whether a ground discharge has an infiltration system
- whether the system is shared, and whether any part of it or the access to it is outside your boundary
The form reminds sellers that buyers can rely on their answers, and that misleading information may lead to a claim for compensation after completion. If you don’t know where your system discharges, find out before you market the house.
What are your options if the system doesn’t comply?
GOV.UK sets out the routes for a septic tank that discharges to a watercourse:
- Connect to the mains sewer, if it is reasonable to do so. Your sewerage company can advise.
- Replace the tank with a small sewage treatment plant.
- Install a drainage field, also called an infiltration system: a series of pipes with holes, laid in trenches so the waste water trickles through the ground for further treatment. You then need to meet the rules for discharges to the ground.
- Apply for a permit if you can’t meet the general binding rules.
GOV.UK adds that you must have building regulations approval to install a new sewage treatment plant, and you may also need planning permission. Get quotes from a specialist before you agree a price with a buyer, so you know what the work involves.
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How is it different in Wales, Scotland and Northern Ireland?
Wales. Natural Resources Wales regulates private sewage systems. You must register your septic tank or small treatment plant as exempt with NRW, and in most cases this is a one-off, free registration. NRW says records of checks and emptying must be kept for 5 years, in case NRW or a prospective buyer asks for them.
Scotland. Citizens Advice Scotland says that if you use a septic tank, you have to register it with the Scottish Environment Protection Agency (SEPA). SEPA says that if you can’t connect to the public sewer, you must apply to it for an authorisation to discharge, and it offers an online check of whether a system is registered. The sale process in Scotland is also different, and our guide to selling a house in Scotland explains it.
Northern Ireland. Septic tank systems need a consent to discharge from the Northern Ireland Environment Agency’s Water Regulation Team, according to the Department of Agriculture, Environment and Rural Affairs.
Wherever you are, ask your solicitor early what paperwork they will need.
How do cash buyers approach a septic tank that needs work?
A septic tank that meets the rules, with a clear maintenance history, need not hold up an open-market sale. Where the system needs replacing, a buyer will want either the work done before completion or a price that allows for it.
A cash buyer can take the work on themselves, which can suit you if you don’t have the time or money to organise it. They will allow for the cost, the disruption and any uncertainty, so offers are usually below what the house would fetch with a compliant system, and a quick sale generally means accepting less than full market value. Our guide to how much cash buyers pay explains how offers are worked out.
If you would rather sell as it is, some of the vetted cash buyers on our panel buy homes with problems like this. You can get offers for my home and tell buyers what you know about the system. It is free, with no obligation to accept. If your house also needs other work, our guide to selling a house that needs renovation may help.
Common questions
Do I have to replace my septic tank before I sell?
Not automatically. In England, a septic tank that meets the general binding rules can stay. If yours discharges directly to a watercourse, it does not meet them, and GOV.UK says you should agree with the buyer who will be responsible for replacing or upgrading it, as a condition of sale.
What is the difference between a septic tank and a sewage treatment plant?
GOV.UK explains that a sewage treatment plant, also called a package treatment plant, treats sewage to a higher standard than a septic tank. That is why, under the general binding rules in England, you must use a small sewage treatment plant if you are discharging to a watercourse such as a river or stream.
How often should a septic tank be emptied?
GOV.UK says you must have the sludge removed before it goes beyond the tank's maximum capacity, and that you should do this at least once a year or in line with the manufacturer's instructions. Keep the receipts, as buyers will want to see the maintenance history.
Do I need to register my septic tank?
It depends where you live. In England, you don't need a permit if you meet the general binding rules. In Wales, you must register your tank or treatment plant with Natural Resources Wales. In Scotland, you have to register it with SEPA, and in Northern Ireland a septic tank needs consent to discharge.
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