Pressure Tank Sizing Calculator and Formula for Philippine Booster Systems

For a fixed-speed commercial booster pump in the Philippines, tank size is drawdown volume divided by acceptance factor: a typical 20 to 30 psi cut-in to cut-out differential gives roughly a 30 to 40 percent acceptance factor, so a pump needing 20 liters of drawdown per minimum run time needs a 50 to 65 liter tank. VFD duplex systems need far less tank volume. Use the calculator below or the formula in this guide to size yours in minutes.

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-sourced pump curves usually come in m3/h, imported 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 sizing comes down to one relationship: nominal tank volume equals usable drawdown divided by the acceptance factor of the tank at your chosen cut-in and cut-out pressures. Drawdown itself is pump flow rate multiplied by the minimum run time you want between pump starts, since starting a pump too often shortens motor and contactor life. Philippine commercial buildings typically run cut-in and cut-out pressures 20 to 30 psi apart, which yields an acceptance factor in the 30 to 40 percent range for a standard diaphragm or bladder tank precharged close to the cut-in pressure. A wider pressure differential raises the acceptance factor and lets you use a smaller tank for the same drawdown, but it also widens the pressure swing felt at the farthest fixture, so the tradeoff has to be checked against the building's plumbing design, not just the tank spec sheet. This is the same formula behind the calculator tool on this page: enter flow, cut-in, cut-out, and minimum run time, and the calculator returns acceptance factor, required drawdown, and nominal tank size in liters. The formula applies whether the tank is sized for a single booster pump or for a duplex or triplex set feeding a commercial, institutional, or industrial building anywhere in the Philippines, from NCR through Luzon, Visayas, and Mindanao. The vessel itself is covered on our hydropneumatic bladder pressure tank page.

Consider a fixed-speed duplex booster pump delivering 150 liters per minute per pump, set to cut in at 40 psi and cut out at 60 psi, a 20 psi differential. At that differential a typical bladder tank precharged near 38 psi runs an acceptance factor of about 33 percent. If the goal is a minimum 1 minute run time per start to protect the motor, required drawdown is 150 liters. Dividing that drawdown by the 33 percent acceptance factor gives a nominal tank size of roughly 455 liters, which in practice rounds up to the nearest stock size, commonly a 500 liter unit. Widening the differential to 30 psi (cut-in 35 psi, cut-out 65 psi) raises the acceptance factor toward 40 percent and drops the same 150 liter drawdown requirement to a roughly 375 liter tank, at the cost of a wider pressure swing at the tap. This is the exact calculation the tool above automates, and it is also the calculation checked by hand on every quote before a tank size is confirmed, because a tank sized purely off a rule of thumb either starts the pump too often or gets oversized and adds unnecessary cost. Run your own flow, pressure, and run-time numbers through the calculator to get a project-specific figure before committing to a tank size; the smaller single-SKU case is covered on the 200L diaphragm pressure tank supplier in the Philippines page.

A fixed-speed pump only has two states, on and off, so the pressure tank has to absorb the full drawdown between starts and the acceptance factor is fixed by the cut-in and cut-out pressures programmed into the pressure switch. A VFD-driven booster pump instead ramps speed to hold a constant discharge pressure, so it does not need a wide pressure differential to avoid short-cycling and can run on a much smaller tank, often sized just to prevent the VFD from hunting at very low flow. This is why a duplex VFD control panel and a fixed-speed duplex panel feeding an identical flow rate will call for noticeably different tank sizes on the same building. JOHOB quotes VFD duplex control panels alongside the booster pumps and pressure tanks together, so the panel's control strategy and the tank size are sized as one system instead of as separate line items that might not match. If a building is being retrofitted from fixed-speed to VFD control, or vice versa, the existing pressure tank usually needs to be resized rather than reused as-is, since a tank sized for a 20 psi differential is typically oversized for VFD service and undersized for a wider fixed-speed differential. 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.

Every pressure tank and control panel JOHOB quotes carries certification paperwork buyers can check before committing budget. Pressure tanks and related storage equipment are supplied through a vetted overseas manufacturer holding ISO 9001 quality management certification, with WRAS-certified panels where the specification calls for potable water contact compliance. Units are TUV SUD tested, and electrical components including VFD and star-delta control panels carry CE marking, matching the standard buyers already expect on imported industrial electrical gear. Where a project specification calls for pressure vessel design compliance, ASME-rated tanks are available. None of this paperwork is unusual for industrial buyers, but it matters most at handover, when a building administrator or PEZA compliance officer asks for it, so JOHOB provides the certification set with the quotation rather than after the purchase order is signed. Buyers sourcing for a PEZA, SBMA, or Clark-registered facility should flag that status at RFQ stage, since it changes the VAT treatment on the invoice (zero-VAT for PEZA and SBMA locators and exporters, 12% VAT otherwise) and does not require separate documentation beyond the standard certification package.

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.

JOHOB does not publish public pricing for pressure tanks or booster systems, since configuration (fixed-speed or VFD, tank material, panel brand, capacity) changes the quote enough that a list price would mislead more than it helps. What is fixed is the process: RFQs get a response within 1 business day, standard ex-stock items ship in 21 to 35 days, and made-to-order configurations (larger tanks, custom panel builds, non-standard capacities) run 45 to 90 days. Pricing is quote-based and reflects the specific flow, pressure, and run-time inputs from the calculator above, plus 12% VAT for standard domestic buyers or zero-VAT for PEZA and SBMA locators and exporters. JOHOB delivers nationwide, covering NCR, the rest of Luzon, Visayas, Mindanao, and PEZA, SBMA, and Clark economic zones. To get an accurate quote, run your numbers through the calculator first and send the resulting flow rate, cut-in and cut-out pressure, and calculated tank size along with your booster pump type, building type, and location; that is enough for a first quote without a site visit.

• 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: September 2026