CLEARMASTERS
The short version
Buying or selling a house with a septic tank: what matters
Plenty of homes with septic tanks and treatment plants sell without any trouble. Problems come from surprises: a septic tank that discharges to a stream, a failed drainage field, missing records or a tank on someone else’s land. Sellers must give the buyer written details of the system. Buyers should get a specialist survey early. Deal with it up front and it rarely holds a sale up.
If you’re buying
Find out what the system is, where it goes, whether it’s shared and whether it meets the rules. Ask for records, and book a septic tank survey as soon as your offer is accepted.
If you’re selling
Pull the paperwork together, write a short description of the system, get it emptied, and fix anything that doesn’t meet the septic tank rules before a buyer’s surveyor finds it.
Interactive checklist
Your septic tank checklist
Choose whether you’re buying or selling, tick things off as you go, and print it to take to a viewing or give to your solicitor.
Buyer’s checklist
Find out what you’re buying
- Confirm the type of system: septic tank, cesspit or treatment plant
Why it matters
They have very different running costs and rules. Our guide to telling them apart has a quick quiz, and a survey will confirm it.
- Find out where the tank and the outlet are
Why it matters
Is the tank on the property, or on a neighbour’s land? Where does the liquid go: a drainage field, a soakaway or a watercourse?
- Check whether it’s shared with other properties
Why it matters
A shared system needs a written agreement covering access, emptying, repairs and how costs are split.
- Check there’s access for a tanker
Why it matters
Emptying needs a tanker to get close enough. Narrow lanes, gates and long distances can make it harder or dearer to empty.
Ask the seller for paperwork
- The written details the seller must give you
Why it matters
Under the general binding rules, the seller must tell you in writing what the system is, where it is, any changes made and its maintenance records.
- Emptying records and waste transfer notes
Why it matters
These show it has been emptied at least once a year, as the rules require.
- Service records, for a treatment plant
Why it matters
Plants need regular servicing. Gaps in the record can mean worn blowers, pumps or alarms.
- Installation date, make and model, and building regulations sign-off
Why it matters
Systems installed since 2015 need building regulations approval and must meet extra rules.
- Any permit or letters from the Environment Agency
Why it matters
If the system needed a permit, it should transfer to you.
Check it meets the rules
- A septic tank must not discharge to a stream or ditch
Why it matters
If it does, it has to be upgraded. Agree with the seller who will pay for it, and when, as part of the sale.
- A treatment plant to a watercourse: does it flow all year?
Why it matters
The rules don’t allow discharges to ditches that dry up or to ponds.
- Will it cope with your plans?
Why it matters
Extensions, extra bathrooms or a bigger household mean more water. The system may need upgrading and the volume recalculating.
Get it surveyed
- Book a specialist septic tank survey early
Why it matters
A general building survey rarely looks inside the tank or at the drainage field. A specialist survey checks condition, outlet and compliance.
- Ask for the tank to be emptied before the survey
Why it matters
An empty tank shows cracks, baffles and pipe connections that a full one hides.
- Use the findings in negotiations
Why it matters
Repairs or an upgrade can be reflected in the price, done by the seller before completion, or covered by a retention. Your solicitor can advise.
Check the legal side
- Rights over any land the tank, pipes or field sit on
Why it matters
If any part is on a neighbour’s land, you need legal rights to use it, maintain it and get access.
- Read the drainage answers in the seller’s property information form
Why it matters
The form asks where the sewerage system discharges to and whether there’s an infiltration system.
- Look at the drainage and water search
Why it matters
It shows whether the property is connected to the public sewer.
Seller’s checklist
Gather your paperwork
- Write a description of the system for the buyer
Why it matters
You must give the buyer written details: what the system is, where it is, any changes and its maintenance records. A simple plan of where the tank, outlet and field are is a big help.
- Find emptying records and waste transfer notes
Why it matters
Buyers and their solicitors will ask. Records showing yearly emptying reassure them.
- Find service records for a treatment plant
Why it matters
A full service history makes a plant much easier to sell.
- Find installation details and building regulations sign-off
Why it matters
Make, model and date installed, plus any completion certificate.
- Find any permit or shared system agreement
Why it matters
If you have a permit or share the system, the buyer will need the paperwork.
Check you meet the rules
- Make sure a septic tank isn’t discharging to a watercourse
Why it matters
If it is, it has to be dealt with. Fixing it before you sell, or agreeing it up front, avoids a sale falling through late on.
- Get it emptied before you market the house
Why it matters
An empty tank looks after the drainage field and makes a survey easier.
- Fix any obvious problems
Why it matters
Smells, soggy ground or alarms will be picked up on a survey. Sorting them early keeps the sale moving.
Get ahead of the buyer
- Consider your own septic tank survey before listing
Why it matters
Knowing the condition and compliance up front lets you price realistically and answer questions with evidence.
- Answer the drainage questions accurately
Why it matters
The property information form asks where the system discharges to and about any infiltration system. Wrong answers can cause problems after the sale.
- Make sure there’s clear access to the tank and covers
Why it matters
Surveyors and emptying crews need to get to it. Overgrown or buried covers slow things down.
What to watch for
Septic tank red flags and deal-breakers
Most issues can be solved. These are the ones that come up most often, and what usually happens next.
Septic tank discharging to a stream or ditch
Doesn’t meet the general binding rules and must be upgraded.
What usually happens: Agree who pays and when. Often a price reduction, or the seller installs a treatment plant or drainage field before completion.
Failed drainage field
Soggy ground, smells, or sewage on the surface.
What usually happens: A replacement field is a significant job. Get a survey and quotes before exchange.
Tank or field on a neighbour’s land with no legal rights
You may not be able to maintain or even access it.
What usually happens: Your solicitor will want the rights put in place, or insurance, before you commit.
No emptying or service records
You can’t tell how well it has been looked after.
What usually happens: Ask for it to be emptied and surveyed. The findings tell you more than the paperwork would.
A shared system with no written agreement
Arguments over emptying and repair costs are common.
What usually happens: Ask for an agreement covering access, maintenance and how costs are shared.
Old soakaway pit instead of a drainage field
May be silted up, and newer soakaways don’t meet the rules.
What usually happens: A survey shows what it is and how well it’s working.
Bigger plans for the house
An extension or extra bedrooms add load.
What usually happens: Check the system’s capacity before you buy, not after.
Treatment plant with a full service history
Well maintained and discharging within the rules.
What usually happens: Check it flows to a drainage field or a watercourse that flows all year.
Septic tank to a working drainage field
Emptied yearly, no signs of problems.
What usually happens: Still worth a survey, but often straightforward.
Step by step
What to do at each stage of the sale
Pick a stage to see what the seller and the buyer should be doing.
Before you list
Seller
- Gather the paperwork and write the system description
- Get the tank emptied
- Consider a survey so there are no surprises
- Sort out any discharge to a watercourse
Buyer
- Ask the agent whether the house has off-mains drainage
- Find out what type of system it is
- Budget for a specialist survey
Offer accepted
Seller
- Send the written system details through your solicitor
- Make sure the buyer’s surveyor can get access
Buyer
- Book a specialist septic tank survey straight away
- Ask for emptying and service records
- Ask whether it’s shared, and where it discharges
Survey and searches
Seller
- Be ready to answer questions about the system
- Arrange access for the surveyor and an empty if asked
Buyer
- Read the survey and the drainage and water search
- Check the property information form answers
- Raise any issues with your solicitor
Negotiation
Seller
- Decide whether to fix issues, reduce the price or agree a retention
- Agree who will upgrade a non-compliant septic tank
Buyer
- Use survey findings and quotes to negotiate
- Agree in writing who does any work, and when
Exchange and completion
Seller
- Hand over manuals, records and the system plan
- Tell the emptying and servicing company the house is changing hands
Buyer
- Make sure any agreed work is done or provided for
- Book your first empty or service
- Keep all the paperwork for when you sell
The law
What the seller must tell the buyer
Under the Environment Agency’s general binding rules, when you sell a property with a septic tank or treatment plant you must give the new owner written details of the system. That should include:
- a description of the treatment system and the drainage system
- where the system and its discharge point are
- any changes made to it
- how it should be maintained, and its maintenance records if you have them
The Law Society’s property information form also asks where the sewerage system discharges to and whether there’s an infiltration system, such as a drainage field. Answer carefully: your buyer relies on it.
Before you commit
What a septic tank survey checks
A building survey looks at the house. A septic tank survey looks at what’s underground: the bit that can cost the most to put right. Book it as soon as your offer is accepted, so there’s time to act on the results.
Septic tank surveysThe tank
Type, size and condition, cracks, baffles and pipe connections, ideally with the tank emptied.
The outlet
Where the liquid goes, and whether the drainage field is working.
The rules
Whether it meets the general binding rules, and what would be needed if it doesn’t.
The pipes
A camera through the drains to spot root damage, blockages and collapses.
The septic tank discharges to a stream?
This is the issue we see most in sales. A septic tank must not discharge to a watercourse, so it has to be replaced with a treatment plant, moved to a drainage field or connected to the sewer. The buyer and seller should agree who will do it, often through the price or before completion. Our septic tank regulations guide explains the options.
New home
After you move in
Do
- Find the tank, the covers and the drainage field, and mark them
- Book your first empty, or a service for a plant
- Keep every waste transfer note and service report
- Leave a treatment plant switched on, even when you’re away
- Read our guide to what not to flush
Don’t
- Build, park or plant trees over the drainage field
- Connect gutters or a new bathroom without checking capacity
- Ignore alarms, smells or soggy patches
- Pour fat, wipes or strong chemicals down the drains
More on keeping it healthy in our guides to what not to flush and how each system works.
Questions answered
Buying and selling FAQs
What should I check when buying a house with a septic tank?
Find out what type of system it is, where the tank and outlet are, whether it is shared, and whether it meets the general binding rules, especially that a septic tank does not discharge to a stream or ditch. Ask for emptying and service records, check legal rights over any neighbouring land, and book a specialist septic tank survey early in the purchase.
Does the seller have to tell me about the septic tank?
Yes. Under the general binding rules in England, the seller must give the new owner written details of the system: what it is, where it is, any changes made to it, and its maintenance records if they have them. The property information form also asks about the drainage.
Can I buy a house with a septic tank that discharges into a stream?
You can, but the system does not meet the rules and must be upgraded, by replacing it with a treatment plant, moving the discharge to a drainage field, or connecting to the sewer. The buyer and seller should agree who will do this as part of the sale.
Who pays to replace a non-compliant septic tank when a house is sold?
It is a matter for negotiation. Often the seller does the work before completion, the price is reduced to reflect the cost, or money is held back as a retention until the work is done. Your solicitor can advise on the best option.
Do I need a septic tank survey when buying a house?
It is strongly recommended. A general building survey rarely looks inside the tank or at the drainage field. A specialist survey checks the condition, capacity and outlet, and whether the system meets the rules, before you are committed.
What if the septic tank is on a neighbour’s land?
You will need legal rights to use the system, maintain it and get access to it. Your solicitor will check the title deeds and may ask for a formal agreement or other protection before you commit.
What if the septic tank is shared with other houses?
Shared systems are common. Make sure there is a written agreement that sets out who can access it, who arranges emptying and repairs, and how the costs are shared. Under the rules, everyone who uses the system is responsible for it.
Should I get the septic tank emptied before selling?
It is a good idea. It protects the drainage field, makes a survey easier because the tank can be inspected properly, and gives you an up-to-date waste transfer note to show the buyer.
Got a different question? Call 03333 233566 or send us a message.