What This Requirement Covers
Where gravity drainage to the public sewer is not possible (typically in basements and low-lying areas), a pumped drainage system is required to lift the foul water to the level of the public sewer or on-site treatment system. Approved Document H addresses the use of pumped drainage systems.
Key Requirements
When Pumped Drainage Is Required
- Basements below the level of the public sewer
- Extensions or conversions where new sanitary facilities are below the drain invert
- Sites where the public sewer is at a higher level than the building
System Types
- Macerator pump: A small pump fitted behind or below a WC that macerates waste and pumps it through a small-bore pipe (typically 22-32 mm). Suitable for single WC additions.
- Sewage pumping station: A below-ground chamber with one or more submersible pumps that collect foul water from multiple appliances and pump it to the gravity drain or sewer. Required for basements with multiple sanitary facilities.
- Grey water pump: Pumps only waste water (not WC waste) from basins, showers, and baths. Smaller and simpler than a sewage pumping station.
Design Requirements
- Pumped systems must comply with BS EN 12056-4 (Wastewater lifting plants)
- A minimum of two pumps must be provided in a sewage pumping station (duty and standby) for reliability
- An alarm system must alert occupants to pump failure
- A non-return valve must be fitted on the discharge pipe to prevent backflow
- The discharge pipe must connect to the gravity drainage system at a suitable point above the flood level
- The pump chamber must be ventilated to prevent the build-up of foul air and gases
Practical Compliance Tips
- Always provide duty/standby pumps in sewage pumping stations; a single pump failure would make the basement unusable
- Install a high-level alarm that alerts occupants to pump failure or high water level in the sump
- Ensure the pump chamber is accessible for maintenance and pump replacement
- Size the pumping station for the expected flow rate, including allowance for simultaneous use of all connected appliances
- Non-return valves are critical; without them, sewage will flow back into the building when the pump stops
- Budget for ongoing maintenance; pumps and non-return valves require periodic inspection and servicing
- Keep the pumping station design, installation certificates, and maintenance schedule for the building file