GPM to LPS Pump Conversion for Philippine Water Systems

To convert US gallons per minute to litres per second, multiply GPM by 0.06309. To go the other way, multiply LPS by 15.85. The exact constant is one US gallon equals 3.785411784 litres, divided by 60 seconds, so 1 GPM equals 0.0630902 L/s. For field work the usable shortcut is: divide GPM by 16 to get LPS, multiply LPS by 16 to get GPM.

That approximation runs about 0.9 percent low, which is well inside the tolerance of any pump curve you will actually buy against. Philippine specifications frequently need a third unit, cubic metres per hour, because most European and Chinese pump catalogs publish duty points that way. The bridges are: 1 L/s equals 3.6 m3/hr, and 1 GPM equals 0.2271 m3/hr. Print the table below and keep it next to the drawings, because you will convert the same duty point three or four times between design and delivery.

The single most expensive mistake in this conversion is not the arithmetic, it is the gallon. A US gallon is 3.7854 litres. An Imperial gallon is 4.5461 litres. The Imperial gallon is 20.1 percent larger, so 1 Imperial GPM equals 0.07577 L/s while 1 US GPM equals 0.06309 L/s. Convert 200 GPM using the wrong gallon and you are off by 2.5 L/s, which is enough to move you a full frame size on a multistage pump or push a duplex set into triplex territory. In practice, Philippine plumbing design leans US: the National Standard Plumbing Code methodology descends from the US model codes, Hunter's Curve tables are published in US GPM, and most consultant drawings issued in Metro Manila follow that convention. Imperial GPM shows up when equipment or documentation traces back to UK, Australian, or older British Commonwealth sources, and it shows up on legacy nameplates. The rule we apply on every RFQ: if a flow figure is written as GPM with no qualifier on a Philippine plumbing drawing, treat it as US GPM, then confirm in writing before anything is ordered. Confirming costs one email. Discovering it after a 45 to 90 day made to order lead time costs a project schedule.

Buyers ask why one project uses three units for the same number. The answer is that each unit arrives from a different document. Plumbing consultants size demand from fixture units and Hunter's Curve, and those tables are published in US GPM, so the design flow lands on the drawings in GPM. Mechanical and civil engineers, along with most PH government and utility submissions, work in SI, so the same duty gets restated in litres per second. Then the pump vendor quotes from a manufacturer curve: Grundfos, DAB, and Speroni publish in m3/hr, and CDL vertical multistage curves are also plotted in m3/hr. Fire protection adds a fourth convention, because sprinkler and fire pump ratings are conventionally listed in GPM at rated pressure. None of these are wrong, they are just three coordinate systems for one duty point. The discipline that prevents errors is to fix one master unit per project, usually L/s because it converts cleanly to both sides (multiply by 15.85 for GPM, multiply by 3.6 for m3/hr), and to write every flow figure on the submittal with its unit spelled out. When JOHOB Hardware Trading reviews an RFQ, we restate the duty in all three units on the quotation so the consultant, the contractor, and the factory are reading the same pump from our pumping and pressure systems range.

A flow conversion alone will not let you select a pump. A duty point is flow plus head, and head units get mixed exactly the same way. The relationships you need: 1 bar equals 10.2 metres of water column, 1 bar equals 14.5 psi, and 1 psi equals 0.703 metres of water column. So a specification calling for 40 psi at the outlet is 28.1 metres of head, and 3 bar is 30.6 metres. Manufacturer curves for the pumps we supply are plotted with head in metres on the vertical axis and flow in m3/hr on the horizontal axis, which is why both conversions have to happen before you can read a curve at all. Two cautions. First, psi at a fixture is residual pressure, not total pump head: total head must add static lift from the tank or suction source, plus friction losses through the riser and fittings. Second, gauge pressure and absolute pressure differ by roughly 1 bar, so confirm which one a European datasheet is quoting. If you are working from tank level and building height rather than from a stated head, our guide on how to size a booster pump for a commercial building walks through the head build up step by step, including static, residual, and friction components.

Here is the arithmetic end to end, using an illustrative duty point rather than a project reference. Suppose a consultant drawing specifies 195 GPM at 40 psi residual for a commercial building booster set. Step one, flow: 195 GPM multiplied by 0.06309 equals 12.3 L/s. Step two, convert to catalog units: 12.3 L/s multiplied by 3.6 equals 44.3 m3/hr, or equivalently 195 multiplied by 0.2271 equals 44.3 m3/hr. Step three, head: 40 psi multiplied by 0.703 equals 28.1 metres, before adding static lift and friction losses, so the true selection head will be higher. Step four, read the curve: you now look for a pump family that covers roughly 45 m3/hr at your final calculated head, and you check that the duty point sits near the best efficiency point rather than at the far right end of the curve. Step five, configuration: a duty of this size is normally handled as a duplex or triplex set from our commercial booster pumps range rather than a single pump, so the per pump flow is the total divided across the running units, with one unit on standby. The standby unit does not change the total flow conversion, only the individual pump selection. Convert first, then select, then decide configuration. Doing it in the other order is how oversized motors get ordered, and our guide on when a VFD is worth it versus a fixed speed pump covers the control side of the same decision.

JOHOB Hardware Trading is a Philippines based industrial equipment supplier serving commercial, industrial, and institutional buyers, with nationwide coverage across NCR, Luzon, Visayas, Mindanao, and the PEZA, SBMA, and Clark zones. We source from Philippine and China factories and deliver with local warranty and after sales support. For pumping and pressure systems that means booster, transfer, and submersible pumps, VFD duplex control panels from our VFD and control panel options, and the piping, valves, and stainless steel flexible hose that go with them, drawing on Grundfos, DAB, and Speroni for established brand requirements and CDL for engineered vertical multistage duties. To convert your duty point and return a selection, send us the flow with its unit stated (GPM, LPS, or m3/hr), the required head or residual pressure with its unit, the static lift from tank or source to the highest fixture, the building type, and the power supply available. We respond to RFQs within one business day. Pricing is quote based and not published, 12 percent VAT applies to VAT registered buyers, and PEZA and SBMA locators and exporters are zero rated. Standard lead times run 21 to 35 days ex stock and 45 to 90 days for made to order equipment, so converting units correctly at the RFQ stage is what keeps that clock from restarting. Process duties like commercial laundry water requirements in the Philippines get the same three unit restatement on the quotation.

• Guide: How to Size a Booster Pump
• Pumping and Pressure Systems
• Commercial Booster Pumps
• Guide: VFD vs Fixed-Speed Pumps
• Guide: Commercial Laundry Water Requirements
• Electrical Panels and Controls

Reviewed: July 2026