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Gas \u00b7 UK

Gas Installation Symbols — UK (BS 1553 / Gas Safe)

These symbols appear on gas installation pipe diagrams, CP12 gas safety records, and commissioning documents in the UK. They follow BS 1553-1 and Gas Safe Register technical standards. Every Gas Safe registered engineer should be familiar with these when producing or reading installation drawings.

BS 1553-1:1977 / Gas Safe Technical Bulletins15 symbols

Pipework

Low Pressure Gas Pipe

Low pressure gas supply pipe (below 75 mbar)

BS 1553-1

Medium Pressure Gas Pipe

Medium pressure gas pipe (75 mbar to 2 bar)

BS 1553-1

Concealed Gas Pipe

Gas pipe run concealed within the building structure

BS 1553-1

Tee Piece

Gas pipe tee junction

BS 1553-1

Test Point

Gas pressure test point nipple

BS 6891 / Gas Safe

Meters & Controls

Gas Meter

Gas supply meter position

BS 1553-1

Emergency Control Valve

Emergency gas shut-off valve (ECV) at meter

BS 1553-1 / Gas Safe

Isolating Valve

Manual gas isolation valve for individual appliance

BS 1553-1

Pressure Regulator

Gas pressure regulator / governor

BS 1553-1

Appliances

Gas Boiler

Wall-hung or floor-standing gas boiler

BS 1553-1 / Gas Safe

Gas Fire / Heater

Gas-fired room heater or decorative fire

BS 1553-1

Gas Hob / Cooktop

Gas cooking hob / cooktop

BS 1553-1

Gas Oven

Gas-fired oven / range cooker

BS 1553-1

Ventilation & Flues

Flue Terminal

Flue / chimney terminal point (balanced or open flue)

BS 5440 / Gas Safe

Air Vent

Fixed ventilation opening for combustion air supply

BS 5440-2 / Gas Safe

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Frequently asked questions about gas symbols

Where are gas installation symbols officially defined?
BS 1553-1:1977 (Specification for graphical symbols for general engineering) covers piping and gas symbols. Gas Safe Register technical bulletins provide additional guidance on diagram conventions.
Do I need to draw pipe diagrams for a CP12?
A CP12 gas safety record requires a schematic showing the installation pipework layout, appliance positions, and safety controls. You don’t need architect-quality drawings, but the symbols should be recognisable.
What is the difference between LP and MP pipe symbols?
Low Pressure (LP) is below 75 mbar — this is standard domestic supply pressure. Medium Pressure (MP) is 75 mbar to 2 bar, used for longer supply runs or commercial installations.

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