Ask the seller what sewage system the property has, where it discharges, which rules or permit apply and when it was last emptied and serviced; in England the seller must give the buyer this information in writing. Then check how the home is heated, what the energy performance certificate says, and whether a grant such as the Boiler Upgrade Scheme could help replace oil or LPG heating later.
When this guide fits
Clues worth recording
- The property is not connected to the mains sewer
- The heating runs on oil, LPG or solid fuel
- There is no mains gas in the village
- The listing says little about drainage or heating
What should the seller tell me about the drainage?
In England, the general binding rules for small sewage discharges say that a seller must tell the new operator in writing that a sewage discharge is in place. That includes a description of the system and its parts, where the discharge point is, any changes made to it, how it should be maintained and any maintenance records. Ask for this early rather than at exchange.
GOV.UK explains that you are responsible for, or the “operator” of, a septic tank or small sewage treatment plant if you own the property that uses it, if your property shares it with others (in which case you are jointly responsible), or if you have an agreement with the owner. Shared systems need clear written arrangements for access, maintenance and cost.
Related guide: buying a house with a septic tank
Which drainage checks are worth paying for?
A standard home survey usually looks at the drainage only at a general visual level. Where the discharge route, condition or capacity is unclear, a specialist inspection can trace the outlet and record what can safely be seen. Two points in England are worth checking straight away: a septic tank must not discharge directly to a ditch, stream or other surface water, and a sewage discharge into a rainwater soakaway installed after December 2007 cannot meet the general binding rules.
Related guide: what a septic tank survey should check
How is the house heated?
Homes without mains drainage are often also without mains gas, so heating may come from heating oil, LPG, electric heaters or solid fuel. Ask which system is fitted, how old it is, when it was last serviced, and what fuel was bought over the last year.
If there is an oil tank, ask where it is, how big it is and how old it is. GOV.UK’s oil storage rules for England apply to a container at a home only if it holds 3,501 litres or more; most domestic tanks are smaller, but the tank’s condition and position still matter to a buyer.
What does the energy performance certificate show?
You can look up a property’s energy performance certificate (EPC) on GOV.UK using the postcode. The register covers England, Wales and Northern Ireland; Scotland has its own register. The certificate shows the heating system and lists recommended improvements, which is a useful starting point for budgeting.
GOV.UK’s “Find ways to save energy in your home” service gives recommendations, with estimated costs and savings, for homes in England and Wales, and points to grant schemes.
Are there grants to replace oil or LPG heating?
The Boiler Upgrade Scheme, open in England and Wales, gives £7,500 towards an air source or ground source heat pump, £5,000 towards a biomass boiler and £2,500 towards an air-to-air heat pump. GOV.UK says that until March 2027 there is an additional £1,500 towards an air source or ground source heat pump if the property is heated by oil or LPG and has no mains gas connection. You must own the property and be replacing fossil fuel heating, and there is one grant per property.
Separately, the government extended the Energy Company Obligation (ECO4), which funds measures for eligible households, to 31 December 2026. Rules and dates change, so check GOV.UK before relying on any scheme.
UK Energy Partnership explains the Boiler Upgrade Scheme and the extra support for oil and LPG homes
For other schemes, see its overview of UK home energy grants
Budget for both systems
Put the running costs of the sewage system (desludging, servicing, electricity for a treatment plant and eventual repairs) alongside the heating fuel and boiler servicing. If either system is near the end of its life, or the drainage needs upgrading to meet the rules, ask your conveyancer how that should be reflected before exchange.
Never enter or lean into a septic tank, treatment plant or chamber when viewing a property. Confined-space gases can be fatal.
Questions homeowners ask
What people usually want to know
Does the seller have to tell me about the septic tank?
In England, yes. The general binding rules say the seller must tell the new operator in writing about the system, its parts, the discharge point, any changes, how to maintain it and any maintenance records.
Can I get a grant to replace an oil boiler?
In England and Wales, the Boiler Upgrade Scheme gives £7,500 towards an air source or ground source heat pump. GOV.UK says that until March 2027 there is an extra £1,500 if the home is heated by oil or LPG and has no mains gas connection.
Where can I see the EPC for a house I want to buy?
On GOV.UK’s “Find an energy certificate” service, which covers England, Wales and Northern Ireland. Scotland has its own register.
Should I get the drainage surveyed before buying?
If the system type, discharge route, condition or shared arrangements are unclear, a specialist inspection can answer questions a general home survey may not.
Sources & review
Evidence behind this guide
Reviewed 2 October 2026. We use primary guidance where available and label trade-body advice clearly.