Article 92 of the Turkish Regulation on Fire Protection of Buildings (BYKHY) defines the fire water tank volume by duration according to the hazard class: low hazard 30 minutes, medium hazard 60 minutes, high hazard 90 minutes. For a preliminary calculation the volume can be taken from the Annex 8/A table (Minimum Water Tank Volume for the Preliminary Calculation of Sprinkler System, Hose Cabinet and Hydrant Design, i.e. a minimum volume), or found by adding the Annex 8/B sprinkler flow, the Annex 8/C hose cabinet flow and, where present, the hydrant flow and multiplying by the duration; if a hydraulic calculation has been made, its result governs.
Article 92 step by step
| Paragraph | Provision |
|---|---|
| 92(1) | The system has at least one reliable water source |
| 92(2) | The part set aside as fire reserve cannot be used for any other purpose |
| 92(3) | Hazard class under Article 19; duration low 30 min, medium 60 min, high 90 min |
| 92(4) | In systems with sprinklers + hose cabinets + hydrants, preliminary calculation with the Annex 8/A table (preliminary calculation, minimum volume); when using the table, the highest level at which sprinklers are used is taken as the height; if a hydraulic calculation has been made, its result applies |
| 92(5) | Preliminary calculation: Annex 8/B sprinkler flow + Annex 8/C hose cabinet flow + hydrant flow (if any), multiplied by the duration |
| 92(6) | Hose cabinets only: in systems complying with TS EN 671-1 and 671-2, the Article 94 design flows × duration; if the use is not in the high hazard class, the hose cabinets may be connected to the domestic water system (Guide explanation: in this case too, the reliable water source requirement of 92(1) must be met) |
| 92(7) | External hydrants only: at least 1,900 l/min × 90 minutes, by hydraulic calculation according to the hazard class. (Added sentence: OG 20/11/2021-31665) For the external hydrant system to be installed in areas covered by Article 7(12), a tank able to supply at least 5,700 l/min × 60 minutes |
Calculation examples (with regulation and guide values)
A facility with external hydrants only (Article 92(7)):
V = 1,900 l/min × 90 min = 171,000 l = 171 m³ (minimum)
If the facility falls within Article 7(12) (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), the 2021 added sentence of Article 92(7) applies to the external hydrant tank:
V = 5,700 l/min × 60 min = 342,000 l = 342 m³ (minimum)
A medium hazard building with hose cabinets only (Article 92(6) and Article 94(b)(5)): the design flow of one hose reel with a round semi-rigid hose is 100 l/min and the medium hazard duration is 60 min. The number of hose cabinets operating at the same time is set by the design; for a single cabinet:
V = 100 l/min × 60 min = 6,000 l = 6 m³
In a sprinklered building the Article 92(5) method is as follows: the sprinkler flow is the design density in Annex 8/B multiplied by the area of operation; the hose cabinet flow in Annex 8/C and, if there are hydrants, the hydrant flow are added, and the total is multiplied by the duration in Article 92(3).
For details of the Annex 8/C table, how to read it together with Annex 8/A (preliminary calculation, minimum volume) and a comparison with the combined water supply rule of TS EN 12845 (clause 9.6.4): Additional Water Demand for Hose Cabinets and Hydrants: BYKHY Annex 8/C and TS EN 12845.
| Building hazard class | Additional hose cabinet flow (l/min) | Additional hydrant flow (l/min) | Duration (min) |
|---|---|---|---|
| Low hazard | 100 | 400 | 30 |
| Medium Hazard 1 and 2 | 100 | 400 | 60 |
| Medium Hazard 3 and 4 | 100 | 1,000 | 60 |
| High hazard | 200 | 1,500 | 90 |
Source: BYKHY Annex 8/C. In Annex 8/B, the design density and area of operation for a wet or pre-action system are, for example, 5.0 mm/min and 72 m² for Medium Hazard 1, 5.0 mm/min and 144 m² for Medium Hazard 2, and 5.0 mm/min and 216 m² for Medium Hazard 3; for storage areas and uses with different characteristics, TS EN 12845 governs (Annex 8/B note).
Example from the BYKHY Guide (an office building in Medium Hazard 2; the guide assumes two hose cabinets operating at the same time):
Q = 5 mm/min × 144 m² (sprinklers) + 2 × 100 l/min (hose cabinets) + 400 l/min (hydrant) = 720 + 200 + 400 = 1,320 l/min
V = 1,320 l/min × 60 min = 79,200 l = 79.2 m³ (43.2 + 12 + 24 m³)
This is a preliminary calculation; if a hydraulic calculation has been made in the final design, the tank volume is taken from that calculation (Article 92(4)).
Which method when?
| Situation | Method | Basis |
|---|---|---|
| Preliminary design, quick sizing | Annex 8/A table (preliminary calculation, minimum volume) | Article 92(4) |
| Final design, hydraulic calculation made | Result of the hydraulic calculation | Article 92(4), last sentence |
| No sprinklers, hose cabinets only | Article 94 flows × duration | Article 92(6) |
| No sprinklers, hydrants only | 1,900 l/min × 90 min and hydraulic calculation; in 7(12) areas at least 5,700 l/min × 60 min for external hydrants | Article 92(7) |
Field note
When using the Annex 8/A (preliminary calculation, minimum volume) table, the "height" row is based on the highest level at which sprinklers are used (Article 92(4)), not the roof level or the building height. The second common mistake is writing the table value onto the tank even though a hydraulic calculation has been made; Article 92(4) takes the hydraulic calculation result where one exists.
Checklist
- Has the hazard class been determined under Article 19 and Annex 1/A, Annex 1/B and Annex 1/C; where there are different hazard classes, has the highest been used (Article 19(1))?
- Has the correct 30/60/90 min duration been selected (Article 92(3))?
- If Annex 8/A (preliminary calculation, minimum volume) was used, was the highest sprinkler level used as the basis (Article 92(4))?
- If there is a hydraulic calculation, has the tank volume been taken from its result (Article 92(4))?
- With hydrants only, is the 171 m³ (1,900 l/min × 90 min) lower limit met; 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 duration is the fire water tank volume based on under BYKHY?
Under Article 92(3), the water tank volume is found on the basis of 30 minutes for low hazard, 60 minutes for medium hazard and 90 minutes for high hazard. The hazard class is determined under Article 19.
Which governs, the Annex 8/A table or the hydraulic calculation?
Under Article 92(4), in systems with sprinklers, hose cabinets and hydrants, the tank volume for a preliminary calculation can be calculated with the Annex 8/A (preliminary calculation, minimum volume) table or by the method in 92(5). If the water tank volume is calculated by a hydraulic calculation, the volume found by the hydraulic calculation governs.
How large should the tank be if a building has external hydrants only?
Under Article 92(7), 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. This means at least 171 m³. Under the sentence added in 2021, for the external hydrant system to be installed in areas covered by Article 7(12), the tank must supply at least 5,700 l/min for 60 minutes; this means at least 342 m³.
References
- Turkish Regulation on Fire Protection of Buildings (BYKHY), Official Gazette 19.12.2007/26735 and amendments; Articles 7(12), 19, 92, 94, Annex 1, Annex 8/A (preliminary calculation, minimum volume), Annex 8/B, Annex 8/C. 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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Download MEP Calc on the App StoreSources are listed in the References section at the end of the article. Quotations from the regulation are unofficial English translations of the Turkish text. This article is for general information; for article numbers, thresholds and exemptions, the current regulation and standard texts published in the Official Gazette govern, and design must be carried out by an authorised engineer.