Article 120 of the Turkish Fire Protection Regulation (BYKHY) covers three tank situations in one place: underground tanks (120(2)), the fittings of aboveground tanks (120(3)) and the places where portable containers and road tankers are filled and emptied (120(4)). It defines what counts as an underground tank, the cover over it, its distance to the surroundings (Annex 12/Ç) and the height of its vent pipe. Fuel stations build their tanks to this article as well (Article 121(4)(a)).
Which text is this based on? This article follows the consolidated text of the Turkish Fire Protection Regulation (BYKHY) as amended up to 09.07.2015 (Official Gazette no. 29411), read together with the BYKHY Guide issued by the Ministry of Environment, Urbanisation and Climate Change in December 2024. The regulation has been amended since 2015, and the Guide itself states that the legislation in force prevails where the two differ. On a real project, check the latest text published in the Official Gazette and confirm with the local authority or fire brigade.
What is an underground tank? (120(2)(a))
Under the regulation, an underground tank is fully buried, has at least 60 cm of soil above it and is also covered by at least 10 cm of concrete. Where vehicles will or may pass over it, the cover changes:
| Case | Cover | Further requirement |
|---|---|---|
| No vehicle traffic | At least 60 cm soil + at least 10 cm concrete | Where no concrete slab covers the tank, the burial area is fenced with wire mesh at least 180 cm high to keep vehicles off |
| Vehicle traffic present or possible | At least 60 cm compacted fill + a 15 cm reinforced concrete slab | The slab extends at least 50 cm beyond the tank footprint in every direction |
Before backfilling, the tank is covered with a non-combustible layer at least 200 mm thick that does not harm its coating (120(2)(f)).
Two differences in the Guide's drawing. The Guide's Figure 120.2 (p. 201) labels the layer round the tank "≥ 2 cm", while both the 2015 text and the Guide's own clause text (p. 200) say 200 mm. The same drawing marks the manhole chamber as Zone 2, whereas clause 120(2)(c) makes it Zone 1. Design to the clause text, not the drawing.
Other underground tank requirements (120(2)(b)–(ğ))
- Distances: Annex 12/Ç applies to inhabited areas and between tanks (120(2)(b)).
- Hazard zones: inside the tank is Zone 0; the maintenance chamber or manhole compartment is Zone 1 (120(2)(c)).
- Tightness: the tank stays tight under expected mechanical loads and in a fire (120(2)(ç)).
- Corrosion: a tank of non-corrosion-resistant material is protected by an undamaged external coating (120(2)(d)).
- Utilities: at least 1 m from public pipes and other networks (120(2)(e)).
- Installation: for a tank not built on site, a competent person confirms the coating is sound during placement, and the tank is lowered into the pit without damage (120(2)(g)).
- Vent pipe: cannot be closed, sized so filling does not pressurise the tank, one per compartment; it must not open into an enclosed space and must discharge to open air at least 4 m above ground, with the end protected from rain and debris (120(2)(ğ)).
Annex 12/Ç: underground tank distances
Distances are the shortest distance from the tank's outer shell (consolidated text p. 72; Guide p. 265).
| Tank volume (litres) | Neighbouring boundary, main road or railway (m) | Between tanks (m) |
|---|---|---|
| 500 or less | 0 | 0 |
| 500 – 3,000 | 3.0 | 1.0 |
| 3,001 – 10,000 | 5.0 | 1.0 |
| 10,001 – 50,000 | 7.5 | 1.0 |
| 50,001 – 120,000 | 10.0 | 1.5 |
| 120,001 – 250,000 | 15.0 | One quarter of the sum of the diameters of adjacent tanks |
| 250,001 – 600,000 | 15.0 | |
| 600,001 – 1,200,000 | 15.0 | |
| 1,200,001 – 5,000,000 | 15.0 | |
| Above 5,000,000 | 15.0 |
Compared with the aboveground table (Annex 12/C), there is no administration-building column and the boundary distance stays at 15 m beyond 120,000 litres. The first two rows overlap at 500 litres (both texts print them this way); for a tank of exactly 500 litres the safe side is 3 m.
Do not confuse Annex 12/Ç with the bulk LPG table (Annex 10): that table uses water capacity in m³ and measures from the tank relief valve and fill point. For liquid fuel tanks the measurement is from the shell.
Aboveground tank fittings (120(3))
- The inside is Zone 0; the tank stays tight under mechanical loads and in a fire ((a), (b)).
- Suitable protection against external and internal corrosion ((c), (ç)).
- Every tank and every compartment has a vent pipe; tanks that do not hold liquids of different hazard groups, and whose contents would not react dangerously if mixed, may share a vent line ((d), (e)).
- Each tank has a level indicator; a glass or similar gauge tube has a quick-closing valve opened only for reading ((f)).
- Every pipe connected to the liquid space has a valve close to the tank, easy to reach and see ((g)).
- Tanks filled with Class I, II and III liquids are protected against electrostatic charging ((ğ)).
For layout, bunding and the protection zone, see the Annex 12/C and bunds article.
Filling and discharge points (120(4))
| Topic | Requirement | Clause |
|---|---|---|
| Static electricity | Measures against electrostatic charging on equipment where portable and road tankers are filled and emptied | 120(4)(a) |
| Environment | Spills kept out of surface water, groundwater and sewers | 120(4)(b) |
| Filling point zone | Zone 1 for a 15 m radius up to 0.8 m above ground, plus a 5 m radius round the fill opening up to 3 m above it | 120(4)(c) |
| Discharge point zone | Zone 2 for a 5 m radius round openings that may release vapour, including the vent opened during discharge, up to 0.8 m above ground | 120(4)(ç) |
The 15 m Zone 1 at the filling point is the rule that takes most space on a site plan: electrical equipment inside it must be explosion-protected, and vehicles may enter only with measures that prevent an explosive mixture (Article 117(1)(b)). The December 2024 Guide also stresses vapour recovery and earthing during filling (p. 192). Vapour displaced while filling is released to open air where it harms no one or, if the building does not allow that, returned through a hose or pipe to the tank being emptied (Article 122(6)).
Common mistakes
- Calling a tank "buried" with thin cover. Without 60 cm of soil and 10 cm of concrete it is not an underground tank under the regulation.
- Sizing the traffic slab to the tank footprint. The slab must extend at least 50 cm beyond it on every side.
- Ending the vent under an eave. It must discharge to open air at least 4 m above ground and never into an enclosed space.
- Running utilities alongside the tank. Keep at least 1 m from public networks.
Station-specific rules are in the Article 121 article and all zone sizes in the hazard zones article.
Frequently Asked Questions
How much cover does an underground tank need under BYKHY?
Article 120(2)(a) requires at least 60 cm of soil plus at least 10 cm of concrete. With vehicle traffic, at least 60 cm of compacted fill and a 15 cm reinforced concrete slab extending at least 50 cm beyond the tank on every side.
How far must an underground fuel tank be from the site boundary?
Annex 12/Ç depends on volume: 0 up to 500 litres, 3 m up to 3,000 litres, 5 m up to 10,000 litres, 7.5 m up to 50,000 litres, 10 m up to 120,000 litres and 15 m above that, measured from the outer shell.
How high must the underground tank vent pipe be?
Article 120(2)(ğ): the vent cannot be closed, must not open into an enclosed space and must discharge to open air at least 4 m above ground, with its end protected from rain and debris.
What is the hazard zone at a tanker filling point?
Article 120(4)(c) makes a 15 m radius up to 0.8 m above ground, plus a 5 m radius round the fill opening up to 3 m above it, Zone 1.
What goes round the tank before backfilling?
Article 120(2)(f) requires a non-combustible layer at least 200 mm thick that does not harm the coating. The Guide's drawing labels it 2 cm; the clause text says 200 mm.
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Download MEP Calc on the App StoreRegulation on Fire Protection of Buildings (BYKHY), Official Gazette 19.12.2007/26735; consolidated text including the amendments of 09.09.2009/27344, 05.04.2012/28255 and 09.07.2015/29411: Article 120 (pp. 45–46), 121(4)(a) and 122(6) (pp. 46–47), Annex 12/Ç (p. 72). BYKHY Guide (Binaların Yangından Korunması Hakkında Yönetmelik Kılavuzu), Ministry of Environment, Urbanisation and Climate Change, December 2024: note to Article 117 (p. 192), Article 120 and Figure 120.2.b (pp. 199–200), Figure 120.2 (p. 201), Articles 120(3)–(4) (p. 202), Annex 12/Ç (p. 265). Page numbers refer to the 72-page consolidated text and to the Guide's own page numbering. The binding text is the regulation in force as published in the Official Gazette.