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Gas Safety

Exam revision materials for Plumbing Level 2&3 and ACS Gas Safety test

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Gas Pipework

New Installation

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Safety Devices and Controls

Air/Gas ratio valves

Appliances Controls

Flame Supervision Devices FSD

Gas Controls

Gas Meter Controls

Safety Cut-off Devices

Spare Part Identification


Open-vented System


Gas Appliances

Ventilation Sizing

Unsafe Situations

Dealing with Unsafe Situations

Emergency Notices and Warning Labels

Gas Leak




Tightness Test

Gas Performance

Gas Rate

Heat Input

Gas Supply

Gas Meters

Gas Pipework

Gas Fittings and Pipes

Gas Supply


New Installation

Pipe Protection

Pipework Sizing

Chimney and Flue


Flue Construction

Flue Inspection and Testing

Flue Terminals

Flue Types


Carbon Monoxide Poisoning

Combustion Process

Natural Gas

Portable Combustion Gas Flue Analysers


Components and Safety Devices

Gas Installation Types

  • low-pressure installation (up to 350mbar)
  • medium pressure-fed installation (up to 8.6bar)
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Underfloor installation

  • 150mm away from electrical meters
  • 25mm away from any electricity supply cables or metallic services
  • BS 6891 - protected against damage and corrosion
  • Notching:
    • MAX depth is D/8
    • S/14<Position from the wall<S/4
  • Drilling:
    • MIN distance apart = 3Ø
    • S/4<Position from the wall<2/5S
    • MAX diameter = D/4
  • Chasing:
    • horizontal = T/6
    • vertical = T/3
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Equipotential Bonding

  • MAX within 600mm of the meter
  • 10mm2 minimum cable size
  • 1200mm - minimum length
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Exterior Pipework

Exterior gas pipework
  • External control valve where the gas pipe leaves the dwelling
  • MIN 375mm depth for buried pipework in driveways, open soil , lawns or gravel paths
  • MIN 40mm depth for buried pipework under pedestrian concrete path
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