Formula & Engineering Reference
| Symbol | Variable | Unit (SI) |
|---|---|---|
| Pmax | Max pressure at the bottom of a zone | bar |
| Pmin | Min pressure at the top of a zone | bar |
| Hzone | Maximum vertical height of one zone | m |
| hfloor | Floor-to-floor height | m |
| nzone | Number of pressure zones | — |
The pressure band is converted to a height with the 10.197 m-per-bar factor, divided by the floor height, and rounded down to whole floors per zone. The number of zones is the total floors divided by that figure, rounded up. The zone table also adds the per-zone head allowance to the target head.
A 20-storey tower with 3.6 m floors, a minimum of 1.5 bar at each zone top and a maximum of 5 bar at each zone bottom, with a 5 m allowance per zone.
Band = 5 − 1.5 = 3.5 bar. Max zone height = 3.5 × 10.197 = 35.7 m. Floors per zone = INT(35.7 / 3.6) = INT(9.9) = 9 floors.
Zones = ⌈20 / 9⌉ = 3 zones: floors 1–9, 10–18, and 19–20. The first two zones span the full 9 floors (28.8 m), and the top zone covers just the last two floors.
Setting the band too wide. A large Pmax–Pmin band gives fewer zones but pushes the bottom-floor pressure toward the overpressure limit, stressing fixtures and risking noise and leaks. The band is a comfort decision, not just an economy one.
Ignoring the incoming utility pressure. If the municipal main already delivers useful pressure, the lowest zone may not need boosting at all. This screening method assumes the zones start from the booster; reconcile it with the available supply pressure.
Forgetting pressure-reducing valves. Zones are often fed from a single high-pressure riser with PRVs stepping the pressure down at each zone. The number of zones here is right, but the actual hardware — dedicated boosters versus PRV take-offs — is a separate design choice.
Treating floor height as uniform. Plant floors, lobbies, and mechanical levels are often taller. A zone sized on a typical floor height can run over its band where the storeys are tall, so check against the real building section.
Leaving demand variability out. Static zoning ignores the fact that pressure sags under flow. The allowance term is there to cover friction and control losses, but heavy simultaneous demand can still pull the top floor below target — confirm with a flowing analysis.
Pressure rises about 0.098 bar per metre of height. One pump for a whole tower would crush the lowest floors to keep enough at the top, so the building is split into vertical zones that each stay within a workable band.
The pressure band converted to metres, divided by the floor height, rounded down. A 3.5 bar band with 3.6 m floors gives about 9 floors per zone.
Often about 5 bar maximum at a zone bottom and 1.5 bar minimum at a zone top — a usable band near 3.5 bar. The exact values follow the owner's standard and fixture needs.
Total floors divided by floors-per-zone, rounded up. A 20-storey building at 9 floors per zone needs 3 zones.
No — it is for early planning and proposals. Final zoning accounts for PRV details, utility pressure swings, demand variability, and the real building section.
High-Rise Zoning Engineering Guide
3 topics • Pressure zoning referenceTall buildings have a pressure problem that short ones never face. Water is heavy, and the deeper a column of it gets, the harder it presses at the bottom. Serve a forty-storey tower from one pump set to satisfy the penthouse, and the ground floor would see pressures that hammer pipes and blow out tap seals. The answer, used in every high-rise, is to slice the building into vertical pressure zones, each kept inside a band that is comfortable from its top floor to its bottom.
This calculator does the first, decisive cut of that exercise: how tall a zone can be before it breaks the pressure band, how many floors that is, and therefore how many zones the building needs. The guide explains the physics behind the band, how the zones stack up, and where this quick method hands off to detailed design.