Pressure Tank Sizing Calculator for Philippine Commercial Booster Systems

This is a working pressure tank sizing calculator built for Philippine commercial and industrial booster systems, not a residential rule of thumb. You enter four numbers: pump flow, cut-in pressure, cut-out pressure, and the minimum run time you want per pump start.

The calculator returns required drawdown in litres, the acceptance factor at your pressure settings, the nominal tank volume you need, and the recommended precharge. Flow can be entered in litres per second, US gallons per minute, or cubic metres per hour, because Philippine projects routinely mix all three. European pump curves from Grundfos, DAB, and Speroni usually come in m3/h, Chinese CDL vertical multistage curves are typically in m3/h as well, and contractor fixture unit worksheets frequently land in US GPM. Pressure can be entered in psi or in bar. Everything is computed in your browser, so nothing is submitted unless you choose to send the result to us for a quotation. The output is deliberately conservative. A tank that is undersized shows up as short cycling, which is a motor and contactor problem rather than a water problem, and it usually appears three to six months after handover once the building is fully occupied. A tank that is oversized costs more and eats plant room floor area, but it does not damage anything. If your result lands between two standard capacities, the calculator rounds up and tells you which two it sat between.

Pressure tank drawdown follows Boyle's law. The usable water is the difference between the water volume held at cut-out pressure and the volume held at cut-in pressure, expressed as a fraction of nominal tank volume. That fraction is the acceptance factor, and it is calculated as 1 minus (cut-in absolute pressure divided by cut-out absolute pressure). Absolute pressure is gauge pressure plus 14.7 psi, or gauge pressure plus 1.013 bar. Two examples show how much the pressure settings matter. At 40 psi cut-in and 60 psi cut-out, the absolute figures are 54.7 and 74.7, so the acceptance factor is 1 minus 0.732, which is 0.268. Only 26.8 percent of the tank is usable water. Widen the band to 45 psi cut-in and 75 psi cut-out and the absolute figures become 59.7 and 89.7, giving an acceptance factor of 0.334, or 33.4 percent usable. Across the pressure settings most Philippine commercial booster sets run, usable drawdown lands between 26 and 40 percent of nominal tank volume. Required drawdown is then pump flow multiplied by the minimum acceptable run time. Nominal tank volume is required drawdown divided by the acceptance factor. Cycle rate is the final check: 3,600 divided by the full cycle length in seconds gives starts per hour, and that figure has to sit under the maximum starts per hour on your motor data sheet. Precharge is set at cut-in minus 2 psi, measured with the tank drained of water. The vessel itself is covered on our hydropneumatic bladder pressure tank page.

Take a fixed-speed duplex booster set where each pump delivers 3.15 litres per second, which is 50 US GPM. The panel is set to 45 psi cut-in and 75 psi cut-out, and the design target is a minimum 60 second run per pump start. Required drawdown is 3.15 multiplied by 60, which is 189 litres. The acceptance factor at 45 and 75 psi is 0.334. Nominal tank volume is 189 divided by 0.334, which is 566 litres. Round up to the next standard capacity and you are specifying roughly 600 litres, either as one vessel or as two 300 litre vessels manifolded together. Now change one input. Leave the pump and the run time alone, and set the panel to 40 psi cut-in and 60 psi cut-out instead. The acceptance factor falls to 0.268 and required nominal volume rises to 705 litres. Same pump, same building, roughly 25 percent more tank, purely because of two pressure switch settings. This is the most common reason a tank that looked correct on the schedule short cycles on site: the tank was sized against one pressure band and the panel was commissioned to another. When we quote a hydropneumatic bladder tank we quote against the pressure settings the panel will actually be commissioned to, and our published starting point for a 5.5 kW class duplex booster is a 500 litre tank before the band and run time are confirmed; the smaller single-SKU case is covered on the 200L diaphragm pressure tank supplier in the Philippines page.

A variable frequency drive changes what the tank is for. On a fixed-speed set, the tank exists to stop the motor starting every time somebody opens a tap, so the tank is sized against run time and starts per hour. On a VFD set, the drive holds pressure by modulating speed, so the tank is sized for sensor stability and for the no-flow hold period before the drive puts the pump to sleep. That is a smaller tank in most cases, but it is not zero. Buildings that drop a VFD set in with no tank at all get pressure hunting at low flow and a drive that never settles. We supply the VFD duplex control panel built by Chutian using Inovance drives, and we spec the tank and the panel together rather than quoting them as unrelated line items. The other input a VFD changes is the pressure band itself. Fixed-speed sets need a wide band to get usable drawdown out of the tank, which is why the 40 to 60 psi and 45 to 75 psi examples above matter so much. VFD sets can run a narrow band because the drive, not the tank, is doing the pressure holding, which is easier on fixtures and on pipe fatigue. If you are still deciding between the two, read VFD versus fixed speed pumps, then run the calculator twice: once at your fixed-speed band and once at the narrow band a VFD allows, then compare the tank volumes and the plant room footprint that come out of each.

Philippine pump specifications arrive in three different flow units, and mixing them is the fastest way to size a tank wrong by a factor of four. Watch for Imperial gallons on older British specifications, which are about 20 percent larger than US gallons, and confirm which one a data sheet means before converting; the full arithmetic is in our GPM to LPS pump conversion guide. The calculator on this page accepts all of these units directly so you do not have to convert by hand, but it is still worth checking the conversion against your pump curve before you commit a number to a schedule. If your pump curve gives duty at a head in metres and your panel is set in psi, convert the head to psi first and confirm the cut-out setting actually sits on the curve rather than past the end of it. The pump-side arithmetic is in how to size a booster pump for a commercial building.

Once the pressure tank sizing calculator gives you a volume, send us the inputs and not only the answer, because the inputs are what we check. What we need: pump flow and head at duty, the cut-in and cut-out settings the panel will be commissioned to, the number of pumps and whether the set is fixed speed or VFD, connection size and orientation, and the plant room access route including door widths and any lift restriction. If the vessel is fire related, tell us whether it serves a fire reserve tank or a sprinkler kit, because that changes the specification path. Pricing is quote based and we do not publish prices. We respond to RFQs within one business day. Standard lead times are 21 to 35 days ex-stock and 45 to 90 days made to order. 12 percent VAT applies to VAT-registered buyers, and zero-VAT supply for SBMA and PEZA locators and exporters applies inside the zones. Equipment we supply carries the certifications the manufacturer holds, which across our pumping and pressure range, including our commercial booster pumps, includes ISO 9001 manufacturer quality systems, TUV SUD testing, CE marking on electrical items, WRAS certified panels on tank products, and ASME on pressure vessels where applicable. We deliver nationwide across NCR, Luzon, Visayas, and Mindanao, including into PEZA, SBMA, and Clark, with local warranty and after-sales support.

• 500 Liter Pressure Tank Price Philippines
• Hydropneumatic Bladder Pressure Tank
• 200L Diaphragm Pressure Tank Supplier
• Hydropneumatic Tank Supplier Philippines
• Guide: How to Size a Booster Pump
• Guide: GPM to LPS Conversion

Reviewed: August 2026