Approved Document H1 is the section of statutory guidance setting out how foul water drainage should be designed and installed to satisfy Building Regulations in England and Wales. The document covers pipe sizing, gradient, trap and vent design, materials, access points and connection to the public sewer. It applies to new builds, extensions, conversions and significant material alterations across Greater London and the rest of England. Compliance is verified by Local Authority Building Control or an Approved Inspector during inspection and testing stages. Practical implications for homeowners include the requirement for properly trapped sanitary fittings, accessible rodding points and pipe runs laid to specified falls. The formal reference document is Approved Document H, Volume 1: Foul water drainage. Designers commonly cross-refer to BS EN 12056 for gravity drainage inside buildings.
Approved Document H1 (foul water)
Guidance on the design of foul water drainage installations to satisfy Building Regulations.
