Gas pipeline pressure levels (NTL, STL, VTL)

Under the Czech Energy Act the gas distribution system consists of high-, medium- and low-pressure pipelines and gas service connections. Network operators use the abbreviations NTL, STL and VTL (low, medium and high pressure) in their drawings and statements. The pressure level tells you at what pressure the pipeline operates.

How to read the abbreviations

• NTL, low-pressure pipeline: up to 5 kPa (0.05 bar),
• STL, medium-pressure pipeline: above 5 kPa up to roughly 3 to 4 bar (sources differ on the upper limit),
• VTL, high-pressure pipeline: higher pressures up to 40 bar (4 MPa),
• VVTL, very high-pressure pipeline: above 40 bar, mainly transmission pipelines.

The boundaries between levels are set by technical rules and vary slightly between expert sources. For a landowner's rights and duties, the decisive threshold is 4 bar, which both the Energy Act and the Building Act use.

Why pressure matters

The protection zone depends on the pressure: pipelines and connections up to 4 bar have 1 m on each side within a municipality's built-up area and 2 m outside it, pipelines above 4 up to 40 bar 2 m and above 40 bar 4 m. High-pressure pipelines from 4 bar also have a safety zone in which building requires the operator's written consent; for a 4 to 40 bar pipeline up to DN 100 it is 8 m, more for larger diameters.

Pressure also affects permitting. A gas connection up to 4 bar and up to 25 m from the existing network is, with the distributor's consent, a minor structure needing no permit; an underground pipeline up to 4 bar is a simple structure.

A main in the street is not a connection

A gas main in the street does not mean the house is connected. The connection is shown by the operator's drawing, a connection document or a gas bill. The connection ends at the main gas valve, where the building's gas installation begins.