External Hydrant 1,900 l/min and 700 kPa: BYKHY Article 95 Rules

Article 95(2) of the Turkish Regulation on Fire Protection of Buildings (BYKHY) requires a hydrant system design flow of at least 1,900 l/min and a hydrant outlet pressure of 700 kPa, and states that the flow is to be increased according to the building hazard class. Article 95(3) ties the distance between hydrants to four risk levels between 50 and 150 m; Article 92(7) defines the water demand of buildings with hydrants only as at least 1,900 l/min × 90 minutes; under the sentence added in 2021, the external hydrant tank in areas covered by Article 7(12) is at least 5,700 l/min × 60 minutes.

Requirements of Article 95

The regulation gives no numerical table for the flow increase by hazard class; the increase is determined by a hydraulic calculation based on the building hazard class (Article 95(2) and Article 92(7)).

Article 95(6) requires the hydrants to be above-ground fire hydrants complying with the relevant Turkish Standards. An underground hydrant is not an option; in the regulation the word "underground" appears only for the isolating valves that make hydrant replacement and maintenance easier (underground, above-ground or both).

When are external hydrants mandatory?

Article 95(7): in settlement areas that contain all kinds of uses and are planned separately from general settlement areas, an external hydrant system is mandatory if the total footprint area of the buildings to be constructed exceeds 5,000 m². Under the sentence added by OG 20/11/2021-31665, an external hydrant system is also installed in areas covered by Article 7(12).

Scope of Article 7(12) (added: OG 20/11/2021-31665): refineries, fossil-fuel power plants, energy generation plants with an installed capacity of 500 MW or more, industrial facilities such as factories with a total enclosed use area greater than 2,000 m², and their storage facilities/yards, built inside or adjacent to forest areas. In these areas the additional measures set out in the regulation are taken.

Link to the water tank

Article 92(7): where a building has only an external hydrant system, the water demand is determined by hydraulic calculations based on the building hazard class, with a capacity able to supply at least 1,900 l/min for 90 minutes.

V = 1,900 l/min × 90 min = 171,000 l = 171 m³ (minimum under the general rule; the exact volume is found by hydraulic calculation according to the hazard class)

Under the sentence added to Article 92(7) by OG 20/11/2021-31665, for the water demand of the external hydrant system in areas covered by Article 7(12), a tank with capacity to supply at least 5,700 l/min for 60 minutes is installed:

V = 5,700 l/min × 60 min = 342,000 l = 342 m³ (minimum in Article 7(12) areas)

For this reason, 171 m³ is not a lower limit that applies in every case; first determine whether the facility falls within Article 7(12).

Field note

In hydrant flow tests it is often forgotten that 700 kPa is the pressure required at the hydrant outlet, and the pump discharge pressure is reported instead; 700 kPa should be shown at the outlet of the hydraulically most unfavourable hydrant after pipework losses are deducted. The second common finding is hydrants placed closer than 5 m to the building facade, where the fire engine cannot approach (Articles 95(1) and 95(4)).

Checklist

• Is the design flow at least 1,900 l/min and increased according to the hazard class (Article 95(2))?
• Has 700 kPa been calculated at the outlet of the hydraulically most unfavourable hydrant (Article 95(2))?
• Does the distance between hydrants suit the risk level (Article 95(3))?
• Are the hydrants 5 to 15 m from the building (Article 95(4))?
• Are the hydrants above-ground fire hydrants complying with the relevant TS (Article 95(6))?
• Without a ring main, is the smallest pipe diameter 100 mm and sized by hydraulic calculation (Article 95(5))?
• Has the external hydrant requirement been checked: 5,000 m² footprint area in a separately planned settlement, or an Article 7(12) area (Article 95(7))?
• With hydrants only, has the tank volume been determined by hydraulic calculation and is it at least 171 m³ (1,900 l/min × 90 min); if the facility falls within Article 7(12), is the external hydrant tank at least 342 m³ (5,700 l/min × 60 min) (Article 92(7))?

FAQ

What is the hydrant system design flow under BYKHY?

Under Article 95(2), the design flow of a hydrant system must be at least 1,900 l/min; the flow is increased according to the hazard class of the building. A pressure of 700 kPa is required at the hydrant outlet. The regulation does not give the increase as a number; it leaves it to a hydraulic calculation based on the hazard class.

How far apart should hydrants be?

Under Article 95(3), the distance between hydrants is taken as 50 m in very high risk zones, 100 m in high risk zones, 125 m in medium risk zones and 150 m in low risk zones. Under Article 95(4), hydrants are normally placed on average 5 to 15 m from the protected buildings.

When is an external hydrant system mandatory?

Under Article 95(7), an external hydrant system is mandatory in settlement areas planned separately from general settlement areas if the total footprint area of the buildings exceeds 5,000 m². Under the sentence added in 2021, an external hydrant system is also installed in areas covered by Article 7(12). Under Article 95(6), the hydrants must be above-ground fire hydrants.

How large should the water tank be at a site with hydrants only?

Under Article 92(7), the general rule is a capacity to supply at least 1,900 l/min for 90 minutes; this corresponds to 171 m³, and the exact value is determined by hydraulic calculation according to the building hazard class. Under the sentence added in 2021, in areas covered by Article 7(12) (facilities inside or adjacent to forest areas such as refineries, fossil-fuel power plants, energy plants of 500 MW or more, and factories larger than 2,000 m²), the external hydrant tank is at least 5,700 l/min × 60 minutes, i.e. 342 m³.

References

1. Turkish Regulation on Fire Protection of Buildings (BYKHY), Official Gazette 19.12.2007/26735 and amendments; Articles 7(12), 92(7), 95(1)–95(7). Amendments: OG 09/09/2009-27344; OG 05/04/2012-28255; OG 09/07/2015-29411; Council of Ministers Decision 2017/10459 of 14/06/2017 (in force 29/06/2017); Council of Ministers Decision 2018/11347 of 05/02/2018 (in force 15/03/2018); OG 04/11/2020-31294 (Presidential Decision 3167); OG 20/11/2021-31665 (Presidential Decision 4825); OG 01/07/2025-32943 (Presidential Decision 10026). Current text (mevzuat.gov.tr)

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