The approved document H – Drainage and Waste Disposal (2015 edition) offers guidance on building regulations that are relevant to drainage, septic tanks and sewage treatment plants.
The main provisions of these regulations are:
The Sewage Treatment Plant must be sited more than 7m from habitable property
- The drainage field must be a minimum of 10 metres from a watercourse, 15 metres from a building and 50 metres from a borehole or spring.
- The drainage field must be designed to BS6297: 2007 and all percolation test results must be submitted.
- The discharge point shall be more than 10m from habitable property
If the discharge is to a drainage field a sampling chamber must be provided before the drainage field.
Drainage fields must be constructed in the aerobic soil layer, i.e. within 700mm of ground level.
Vents and Stench Pipes
Drugo air admittance valves see page 7 of the AB Drugo Air Admittance Valves Datasheet. ‘5.9 – Air admittance valves should not be used when the discharge stack provides the only ventilation to septic tanks or cesspools‘ this also applies to Package Sewage Treatment Plants.
It is vital in order to prevent smells that the pipework to the septic tank or package sewage treatment plant are adequately vented.
How to secure consent to to build over or close a public sewer or lateral drain (United Utilities)
The first thing to do is check if your new building is subject to the Building Regulations. If it is then you may need to utilise UU’s Buildign Control PRotocol Agreement through your building control inspector and you will need to fill in the Declaration of Works Form. For more information see page 6 of the guidance document Building Over Sewers