How to Size a Booster Pump for a 15 Storey Building in the Philippines

Most booster pump sizing guides assume a building short enough to run as one pressure zone. A 15 storey stack is not that building. At a typical 3.0 to 3.5 m floor-to-floor height, the topmost fixture sits 45 to 52 m above the pump room, and a pump that delivers enough head to serve it will push roughly 64 to 74 psi of static pressure onto the ground floor fixtures before any friction loss is subtracted. That is above the working limit most fixture manufacturers publish. So the first decision on a 15 storey job is not which pump, it is how many pressure zones. The second change is control, because demand swings hard between the 6am peak and 2am near-zero. The sizing work below therefore produces four outputs, not one: peak flow, total dynamic head, the zone split, and the control strategy. The generic method sits in our general commercial booster pump sizing guide; this page runs the 15 storey numbers end to end.

Total dynamic head (TDH) is static lift plus friction loss plus the residual pressure you must still have at the highest fixture. Static lift is the vertical distance from the suction water level in the cistern to the highest fixture served, not to the roof. For a 15 storey building at 3.2 m floor-to-floor with the pump room in a basement 3 m below grade, that is (15 x 3.2) + 3 = 51 m. Residual pressure at the top fixture: plan for 15 to 20 psi (10.5 to 14 m) for tank-type water closets, showers, and lavatories, and 25 psi (17.5 m) if any top-floor fixture is a flushometer. Friction loss: size the riser so velocity stays at or below 2.4 m/s, then compute loss along the longest run including fittings; on a well-sized 15 storey riser that lands around 10 to 15 percent of static, so 6 to 8 m.

Carry 70 m forward without a blanket safety margin, because oversizing here is what produces short-cycling later.

Flow does not scale with the number of fixtures, it scales with how many are likely to run at once. Tabulate Water Supply Fixture Units (WSFU) for every fixture, then convert the total to peak simultaneous demand through Hunter's Curve, which is the method the Philippine National Standard Plumbing Code follows. Take an illustrative 15 storey residential tower with 8 units per floor, so 120 units. A typical unit with one tank-type water closet, one lavatory, one kitchen sink, and one shower tabulates at roughly 6 WSFU, giving 720 WSFU before common areas; add the lobby toilets and amenity level and you are near 780 WSFU. Read that against the flush-tank branch of Hunter's Curve and peak demand lands around 130 to 145 gpm, which is 8.2 to 9.1 L/s or 30 to 33 m3/h. If your figures are in gpm and your supplier quotes in L/s, our gpm to L/s pump conversion reference covers the swap. Two numbers now carry forward: about 32 m3/h and about 70 m TDH.

A single zone serving all 15 floors puts roughly 74 psi of static on the ground floor when the top floor is satisfied, so the stack gets split. The usual arrangement is a low zone covering floors 1 to 8 and a high zone covering floors 9 to 15, each with its own booster set fed from the same ground level cistern. The low zone sizes on 8 x 3.2 + 3 = 28.6 m static, giving roughly 45 m TDH after residual and friction. The high zone keeps the full 51 m static and the roughly 70 m TDH from Step 1. Flow splits with the fixture count, each zone recalculated through its own WSFU tabulation rather than by halving the building total. The alternative is one high-zone pump plus pressure reducing valves on the lower floor branches. That is cheaper to install, but every litre on the lower floors is pumped to 70 m and then throttled back, so you pay for the wasted head for the life of the building. On new-build 15 storey projects we quote the two-zone arrangement by default and price the PRV option beside it. The same zoning logic decides a condominium booster pump replacement in Manila when an existing single-zone tower is being re-equipped.

Hydraulic power is flow times head times density times gravity. At 32 m3/h (0.0089 m3/s) and 70 m, that is 1000 x 9.81 x 0.0089 x 70, about 6.1 kW of water power. Divide by a realistic vertical multistage pump efficiency of 0.60 to 0.68 and you need roughly 9 to 10 kW at the shaft, so the high zone lands on an 11 kW frame. Configuration comes next. A duplex set (duty and standby, each rated for the full 32 m3/h at 70 m) is the minimum acceptable arrangement on a residential tower. A triplex set with three pumps each rated near 50 to 60 percent of peak handles the overnight low-flow condition far better, because one small pump can hold pressure at 2am instead of an 11 kW unit cycling every few minutes. On a 15 storey stack the demand swing is wide enough that we recommend triplex with VFD control on both zones; the payback cases are set out in our guide on VFD versus fixed speed pump control. We supply complete commercial booster pump systems from Grundfos, DAB, Speroni, and CDL, matched to Chutian panels running Inovance drives through our VFD duplex control panels, with hydropneumatic bladder tanks sized to absorb the residual cycling.

A correctly sized booster set still fails if the cistern behind it runs dry during the morning peak or if the suction level drops far enough to cavitate the pump. Storage sizing starts from daily demand rather than peak flow: tabulate occupancy and the agreed per-capita allowance, and hold at least one full day of demand at ground level, then check the figure against the fire reserve requirement, because on most towers the fire reserve and the domestic reserve share a structure with a divider and a dedicated fire draw-off. Confirm the suction condition too: verify NPSH available at the lowest working level exceeds the NPSH required from the pump curve at peak flow, with margin. If your project needs the storage as well as the pumps, modular water storage tanks are supplied through our sister brand TankSmith in FRP, GRP, hot dip galvanised, and stainless panels from partner factories.

We can return a sized recommendation from a short list of inputs: the floor count and floor-to-floor height, the pump room level relative to grade, the WSFU tabulation or at minimum the unit count and fixture schedule per unit, the riser diameter and material, the height to the highest fixture, whether any flushometers are served, the available cistern volume and its lowest working level, and the incoming supply pressure. If the tabulation is not ready, send the architectural plans and the plumbing layout and we will do the WSFU work. We respond to RFQs within one business day. Pricing is quote-based and we do not publish price lists. Standard lead times are 21 to 35 days for ex-stock configurations and 45 to 90 days for made-to-order sets. VAT-registered buyers are billed 12% VAT, while PEZA and SBMA locators and registered exporters are invoiced zero-rated. We deliver nationwide, covering NCR, the rest of Luzon, Visayas, Mindanao, and the PEZA, SBMA, and Clark zones, with local warranty and after-sales support on supplied equipment.

• Guide: How to Size a Booster Pump (General Method)
• Multistage Pressure Booster for a 20 Storey Condominium
• Commercial Booster Pumps
• Condominium Booster Pump Replacement Manila
• Guide: Duplex vs Triplex Booster Pumps
• Guide: VFD vs Fixed Speed Pumps