Pump Station Calculator — Chamber Size, Pump Duty & Rising Main

A pumping station is needed when the drainage cannot flow by gravity to the public sewer — typically when the sewer is higher than the building drainage, or when the building is a long distance away and sufficient gradient cannot be achieved. They are common for basement drainage, low-lying sites and rural properties.

Approved Document H1 (para 2.39) requires the effluent receiving chamber to contain 24-hour inflow so that effluent can be stored if the pump fails. For domestic use the minimum daily discharge is taken as 150 litres per head per day, so a 5-person dwelling needs at least 750 litres (0.75 m³) of storage. Separately, the operational dead-band between pump start and stop levels (inflow × retention time) must be large enough to limit pump cycling — typically a 4-minute retention at peak inflow — but this dead-band is a check, not the chamber size.

Total dynamic head is the sum of static head (the vertical height the pump lifts water) plus friction head (energy lost to pipe friction). The pump must overcome TDH to deliver the required flow. Friction head is flow-dependent and is worked out here with the Hazen-Williams equation (C = 150 for new polyethylene). Rising main bends add equivalent pipe length — a 90° bend is allowed roughly 1.8 m of equivalent length here, in line with published fittings tables (~1.7-2.1 m).

Sewers for Adoption (now Design and Construction Guidance) requires twin pumps for adoptable pump stations — one duty, one standby. For private domestic stations, a single pump is acceptable but twin pumps provide resilience. A non-return valve (NRV) is always required on each rising main.

The Sewerage Sector Guidance (Appendix C) and Sewers for Adoption / Design and Construction Guidance set a self-cleansing minimum of 0.75 m/s for foul rising mains (1.0 m/s for surface water). Below this, solids settle in the pipe and cause blockages. A practical design band is about 0.75–1.8 m/s; keep the maximum below ~3 m/s to limit friction loss and water-hammer risk. MDPE pipe is designated by outside diameter, so velocity is worked out on the smaller internal bore (63 mm OD SDR11 = 51.4 mm bore). Use our Rising Main Calculator to determine the correct pipe size and friction losses.