Sewerage Plants - General Binding Rules - England
If you live in the countryside you may have a sewerage treatment plant.
See below the Government's Environment Agency weblinks setting out the rules regarding installation and sewerage discharge to ground and surface water.
If you don't comply you will have issues on re-sale.
Discharge to Ground
https://www.gov.uk/guidance/general-binding-rules-small-sewage-discharge-to-the-ground
Discharge to Surface Water
https://www.gov.uk/guidance/general-binding-rules-small-sewage-discharge-to-a-surface-water