High-Rise Building Domestic Water Boosting in Singapore

Scenario

42-storey mixed-use tower (retail + residential) in Tanjong Pagar, Singapore. Local PUB regulations require minimum 3.5 bar (≈35.7 m) residual pressure at all outlets, including top-floor units. Constraints: tight mechanical penthouse space (<8 m²), noise limits ≤45 dB(A) at adjacent residences, and mandatory dual-pump redundancy per PUB Code of Practice CP 137. Existing rooftop tank is retained but undersized for peak morning demand.

Given Data

• Static Head: 32 m (tank elevation above ground floor datum)
• Pipe Length: 195 m (vertical + horizontal equivalent, per hydraulic model)
• Pipe Diameter: 80 mm (stainless steel 316, schedule 10S, C = 120)
• Flow Rate: 1,850 L/min (design peak for 210 units + retail loads)
• Elevation Difference: 142 m (ground floor to roof tank spillover level)
• Pump Efficiency: 78% (premium IE4 canned-motor vertical multistage pumps with acoustic enclosures)

Calculation

Using the Pump Selection Calculator:

1. Friction head loss: Input yields 41.6 m (accounting for fittings, valves, and stainless roughness).
2. Total Dynamic Head (TDH) = Static Head (32 m) + Friction Loss (41.6 m) + Elevation Difference (142 m) = 215.6 m.
3. Required Motor Power = (1000 × 9.81 × (1850/60,000) × 215.6) / (0.78 × 1000)
   Q = 1850 L/min = 0.03083 m³/s →
   (1000 × 9.81 × 0.03083 × 215.6) / 780 = 83.4 kW (for single pump). With redundancy, two parallel pumps sized at 50% oversize each → 46.2 kW/pump.
4. Recommended Pump Capacity = 1,850 L/min × 1.15 (PUB-required safety margin) = 2,127.5 L/min, rounded to 2,130 L/min.

Result and Decision

Specified twin vertical multistage pumps (Grundfos CRNE 120-5, 45 kW each, 2,200 L/min @ 220 m TDH), mounted on spring-isolated skids with integrated VFDs and soft starters. System includes intelligent pressure cascade control and real-time leak detection. Passed PUB commissioning tests in Jan 2024 with measured residual pressure of 3.8 bar at 42nd floor and noise level of 42.3 dB(A) at nearest bedroom wall.

Lesson

Regulatory safety margins (e.g., PUB’s 15%) are non-negotiable inputs—not post-calculation add-ons. Integrating them into the ‘recommended pump capacity’ step prevents costly redesigns during statutory approval.