Sector·4 min read
Business Center and Residential (High-Rise) Fire Safety
In high-rise buildings such as business centers and residences, the hardest engineering problem in fire safety is water pressure. To provide adequate pressure at the highest, most remote sprinkler, the pump must produce high pressure; on the lower floors this pushes the static pressure above the strength limit of the components (around 12 bar). This article covers BYKHY high-rise application detail, pressure zoning, the need for and selection of pressure reducing valves (PRV), intermediate pump/break tank solutions, and the fire safety lobby with stair pressurization.
A-Pro Engineering
High-rise buildings such as business centers and residences pose their hardest fire-safety engineering problem in water pressure. This article covers first the BYKHY high-rise application detail, then the pressure challenges and the pressure reducing valve (PRV) solutions.
High-rise and mandatory systems under BYKHY
In BYKHY a high-rise is, in short, a building whose building height exceeds 21.50 m (roughly 7–8 storeys); a structure height of 30.50 m is also an important threshold. Typical requirements:
- Sprinkler — non-residential structure height > 30.50 m, hotel/dormitory > 21.50 m (Article 96),
- Hose cabinet / standpipe — > 21.50 m (Articles 74–77),
- Fire-department water connection / dry riser (Article 97),
- Fire detection and alarm (Article 75),
- Fire safety lobby + stair pressurization (Article 34),
- Compartment — at most every three floors (Article 24).
We covered which structure needs which system in detail in our general article.
The real challenge: pressure created by height
Because of the weight of the water column, each ~10 m of height ≈ 1 bar of static pressure. This creates two opposite problems on the same vertical line at once:
- Too little at the top — the highest (most remote) sprinkler/cabinet needs adequate working pressure → the pump must produce high pressure.
- Too much at the bottom — when this pressure adds to the static head on the lower floors it exceeds the strength of pipe, valve, sprinkler and hose-connection components (≈ 12 bar / 175 psi for common components).
We covered sprinkler water demand and hydraulic calculation in a separate article.
Solution 1 — Pressure zoning
The building is divided vertically into zones; floors are grouped so that each zone’s static pressure stays below the component limit (roughly one zone every 10–12 floors). Each zone is fed from its own riser, within its own pressure range.
Solution 2 — Pressure reducing valve (PRV)
Wherever the static pressure exceeds component strength, a pressure reducing valve (PRV) is used. Typical locations:
- Zone riser inlets,
- Floor control valves,
- Hose cabinet / fire-department hose connections.
Critical distinction: a “pressure restricting” valve only reduces the dynamic (flowing) pressure; at no-flow it does not reduce the static pressure, and it is usually inadequate in a high-rise. That is why true “pressure reducing” valves, which reduce both static and dynamic pressure, are preferred. Each PRV must be correctly sized for its outlet pressure and flow and be testable. See our separate article for valve sets and control assemblies.
Solution 3 — Intermediate pump, break tank and rooftop tank
In very tall buildings water is carried up by pumping in series:
- Intermediate (booster) pump and break tank — upper zones are re-pressurized from an intermediate floor,
- Rooftop gravity tank and express riser — adequate, stable pressure to the upper zones,
- High-pressure class (300 psi) components in the upper zones where needed.
Fire pump and water tank
A high-rise requires a redundant pump station: main pump (electric) + standby pump (diesel — during a power outage) + jockey pump. Sizing is based on EN 12845 / NFPA 20. The water tank volume is calculated according to hazard class and required operating time (sprinkler + hose-cabinet flow × duration).
Two different “pressures”: water vs. air
The second topic not to confuse is smoke-control pressurization: escape stairs and the fire safety lobby are kept at positive pressure with clean air so that smoke cannot pass in from the adjacent floor. This differs from the hydraulic system that manages the pressure of the suppression water, but in a high-rise the two are designed together.
Summary
High-rise (business center/residence) fire safety requires, on top of the BYKHY mandatory systems, a hydraulic design that solves the pressure problem created by height: pressure zoning + pressure reducing (PRV) valves + intermediate pump/break tank/rooftop tank provide both adequate pressure at the top and safe pressure at the bottom; this is accompanied by a redundant fire pump, the correct water tank and stair pressurization. We also covered how a sprinkler works in a separate article. At A-Pro Engineering we design integrated pressure zoning, PRV selection, pump stations and standpipes for high-rise buildings; contact us for your project.
This content is for information only. Binding design must be done project-specifically with a hydraulic calculation, based on the actual building height, hazard class and component pressure classes and the editions in force of BYKHY, EN 12845 and NFPA 13/14/20.
© 2027 A-Pro Mühendislik. This is original technical content produced by A-Pro Engineering; all rights reserved. Copying, reproducing or republishing it in whole or in part without attribution and permission is prohibited.
Frequently asked questions
What is a high-rise under BYKHY and which systems are mandatory?+
In BYKHY a high-rise is, in short, a building whose building height exceeds 21.50 m (roughly 7–8 storeys); a structure height of 30.50 m is also an important threshold. Typical requirements in high-rise buildings: an automatic sprinkler system — for non-residential structures once structure height exceeds 30.50 m, for accommodation such as hotels/dormitories once it exceeds 21.50 m (Article 96) —, hose cabinet/standpipe (above 21.50 m, Articles 74–77), fire-department water connection/dry riser (Article 97), fire detection and alarm system (Article 75), fire safety lobby and escape-stair pressurization (Article 34), and a fire compartment at most every three floors (Article 24). In the mixed business-center/residence use, the risk of each portion is assessed separately.
Why is water pressure a problem in a high-rise?+
Because of the weight of the water column, each roughly 10 metres of height creates about 1 bar of static pressure in the system. In a tall building, to provide the required working pressure at the highest (most remote) sprinkler or hose cabinet, the pump must produce very high pressure; but as you descend to the lower floors this pressure adds to the static head and exceeds the strength limit of components such as pipe, valves, sprinklers and hose connections (about 12 bar / 175 psi for common standard components). So on the same vertical line you get 'too little' pressure at the top and 'too much' at the bottom at the same time. The solution is to manage these two ends separately.
Why and where is a pressure reducing valve (PRV) used?+
A pressure reducing valve (PRV) is used to bring the high pressure at a point down into the safe working range of the components, and it is indispensable for the lower zones of a high-rise. It is needed wherever the static (no-flow) pressure exceeds component strength; typical locations are zone riser inlets, floor control valves and hose-cabinet/fire-department hose connections. There is a critical distinction here: a 'pressure restricting' valve only reduces the dynamic pressure during flow, it does not reduce the static pressure at no-flow, and it is usually inadequate in a high-rise. That is why true 'pressure reducing' valves, which reduce both static and dynamic pressure, are preferred. Each PRV must be correctly sized for its outlet pressure and flow, and be testable.
By what methods is the pressure problem in a high-rise solved?+
The solution is not a single device but a layered hydraulic design. 1) Pressure zoning: the building is divided vertically into zones; floors are grouped so that each zone's static pressure stays below the component limit (≈12 bar) — roughly one zone every 10–12 floors. 2) Pressure reducing valves (PRV): in the lower zones and at floor/hose connections with high static pressure, the pressure is brought into the safe range. 3) Intermediate (booster) pump and break tank: in very tall buildings water is carried up by pumping in series to the roof/intermediate floors; each zone is fed from its own pump or a rooftop tank. 4) A rooftop gravity tank and an express riser provide adequate pressure to the upper zones. 5) High-pressure class (300 psi) components are used in the upper zones where needed. Together these methods provide both adequate pressure at the top and safe pressure at the bottom.
How are the fire pump and water tank designed in a high-rise?+
A high-rise requires an uninterrupted, reliable water source, so the fire pump station is installed with redundancy: a main pump (electric), a standby pump (usually diesel — runs during a power outage) and a jockey pump that makes up small pressure losses are provided together. Pumps are sized to EN 12845 and/or NFPA 20 principles. The water tank volume is calculated according to the building's hazard class and the required operating time (sprinkler + hose-cabinet flow × duration); we covered water demand in a separate article. In very tall buildings, break tanks and a rooftop tank are part of the system for both pressure zoning and redundancy.
Besides water pressure, what other 'pressure' systems exist in a high-rise?+
There are two different 'pressure' topics in a high-rise and they must not be confused. The first is the water (hydraulic) pressure and pressure reducing valves that are the main subject of this article. The second is air pressurization for smoke control: escape stairs and the fire safety lobby (Article 34) are kept at positive pressure by injecting clean air so that smoke cannot pass in from the adjacent floor; the evacuation route stays smoke-free. These two systems serve different purposes (one manages the pressure of the suppression water, the other protects the escape route from smoke) but they are designed together in high-rise fire safety.
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