Pump sump storage and pumping capacity for rainwater entering basements and other underground facilities, to PUB Code of Practice on Surface Water Drainage (COP-SWD) Cl. 4.9 and Cl. 10. Yellow cells are inputs.
| Item | Formula / requirement | Source |
|---|---|---|
| Need for pumped drainage | Underground facilities shall as far as possible prevent storm water ingress; where it cannot be prevented, minimise the catchment and provide an adequate pumped drainage system, segregated from the surface drainage catchment | COP-SWD Cl. 4.9.1 |
| Pumping capacity | P = I·A / (3.6×10⁶), with I ≥ 150 mm/hr over the entire source catchment area (P m³/s, I mm/hr, A m²) | COP-SWD Cl. 10.1(a) |
| Sump storage | Store the total inflow from the entire source catchment for at least 3 hours (or longer if the QP or PUB requires), based on maximum recorded rainfall: 3 h 196.9 mm; 4 h 210.6 mm; 5 h 253.4 mm; 6 h 281.9 mm; 12 h 376.7 mm; 24 h 533.2 mm. V = C·d·A | COP-SWD Cl. 10.1(d) |
| Standby pumps | General developments: at least N duty + 1 standby. All other developments: at least N duty + N standby (N = pumps needed for the design capacity) | COP-SWD Cl. 10.1(b), Addendum No. 3 |
| Pump control | Automated device to start pumping at times of storm water ingress | COP-SWD Cl. 10.1(c) |
| Sump base | Gradient 1:40 or steeper | COP-SWD Cl. 10.1(e) |
| Runoff coefficient | Paved/roofed 1.00; urban 0.90; vegetated/pervious 0.45. Cl. 10 formulas carry no C, so C = 1.00 is used unless the QP justifies otherwise | COP-SWD Cl. 7.1.2 |
| Minimum requirements | Cl. 10 criteria are minimums; the QP is fully responsible for the complete design of the pumped drainage system | COP-SWD Cl. 10.2 |
| Covered area allowance (% of covered area added to catchment, e.g. for wind-driven rain) | A = A1 + A2 × % | Not stated in COP-SWD. Designer's assumption; QP to justify |
This calculator is a design aid. The Qualified Person remains responsible for the design and must check every input and result against the current COP before submission. Pump selection is by the M&E PE.