Routing, support and protection

Where you run pipework decides how safe it stays over its life: whether it can be damaged, corroded or knocked, and where gas would go if it ever leaked. The law sets the principle (GSIUR regs 18–20), and BS 6891 gives the detail.

General rules

• Safe position. Pipework must not go anywhere it can't be used safely, given other pipes, drains, cables and electrical equipment, and the building structure (reg. 18).
• Don't weaken the building. It must not impair the structure, fire resistance, damp-proof course, or the thermal or sound insulation (reg. 20; BS 6891 8.1.3).
• Keep gas out of cavities. Route pipework so escaping gas can't get into cavities.
• Keep the bore clear. No kinks, burrs or debris, and keep dirt and water out while you work.
• Protect it where it could be damaged, and avoid places where getting at it later could affect the building's structure.
• Not in air ducts. Never run gas pipe in a ventilation or air-conditioning duct.
• Keep it apart from other services, and don't let it touch metal fittings that could cause electrolytic corrosion.

Other services

Where pipework isn't separated from electrics by an insulating enclosure, barrier, trunking or conduit, keep it:

• at least 150 mm from electricity meters, main cut-outs, main isolators, distribution boards and consumer units
• at least 25 mm from switches, sockets and cables.

Where that isn't practicable, sheathe the pipe in insulating material rated at 230 V or more, or put an insulating panel between them. Don't position pipework so it stops a switch or socket being used. Don't bury pipework in a floor with electric underfloor heating unless the heating is permanently disconnected. Where electro-osmotic damp-proofing is fitted, keep all metal gas pipework above ground-floor level.

Corrosion protection

Pipework at risk of corrosion, such as pipe buried in floors, walls or the ground, must be made of a corrosion-resistant material or protected, including the joints.

• Use factory-protected pipe where practicable. Check its coating for cuts and make good any damage, to the manufacturer's instructions.
• Apply site protection only to clean, dry pipe, and only after a successful tightness test. Wrapping tape should overlap by at least 55%, giving a double layer. Yellow ochre is the preferred colour for wrapping and coatings.
• Pipe in a fireplace opening must be factory protected or wrapped, because soot and debris can be very corrosive. Coastal areas can be corrosive too.

Supports

Support pipework to the manufacturer's instructions or, if there are none, at no more than the intervals in BS 6891 Table 4. For example:

Supports must suit where they're used (for example corrosion-resistant or UV-stabilised outdoors) and stop the pipe touching surfaces that could corrode it. Where the meter isn't securely fixed, for example to a bracket, the first 600 mm of pipework from the meter installation must be rigid and securely fixed.

• Where the meter installation includes a flexible connection, the pipework before and after it needs particular care. Without extra support, the flexible connection lets a pipe extension act as a lever on its one fixed end, so clips may be needed.
• After any alteration, make sure the installation is secure, and that no undue stress is put on the pipe, fittings or meter installation.
• If existing pipework isn't adequately supported, tell the customer or responsible person.
• If the gas network's service pipe is insecure, report it to the gas network and get a reference number.

Outside, above ground

Protect external pipework against mechanical damage (for example in a car port) and against corrosion. Copper exposed to the weather doesn't normally need extra protection unless there's another source of corrosion. Bear in mind that copper may be stolen.

Buried in the ground

Buried metal pipework is only installed where it's appropriate, after a risk assessment, and with an inspection plan given to the customer. It must be pre-insulated copper (BS EN 13349), CSST approved for direct burial, or pipe in a buried outer sleeve or channel that can be inspected. Ordinary steel tube must not be buried. PE may be used outside, but only above ground where it rises to change to metal, shielded from sunlight and damage, and never solvent welded.

Minimum depth of cover (Table 5) ranges from 375 mm in private gardens to 600 mm under drives that heavy vehicles may use, and more on farmland. Lay the pipe on fine, stone-free material with at least 75 mm of it on top, keep joints to a minimum, and keep 250 mm from foundations and other services where practicable. Leave joints exposed until the tightness test is done. Lay yellow "gas" marker tape 100–300 mm above the pipe, unless the route is recorded or obvious.

Sources: GSIUR 1998 regs 18, 20safe use, protection of buildings BS 6891:2015 8.1general, corrosion BS 6891:2015 8.2600 mm BS 6891:2015 8.4.1–8.4.2, 8.4.4other services BS 6891:2015 8.8, Table 4supports Gas Safe Register TB 156 (2019)adequate support BS 6891:2015 8.12–8.15, Table 5external, buried, PE CCN1 Issue 16 §5assessed

▸Tutor notes

• Take learners round a kitchen (or a photo of one) and have them mark where pipework could and couldn't run, and the clearances to the consumer unit and sockets.
• Ask why protection goes on only after the tightness test.
• Show a photo of a meter with a 1.2 m outlet pipe clipped only at the far end. Using TB 156, ask whether it's adequately supported, and why the Table 4 spacing alone doesn't answer that.
• CCN1 §5 covers external surface-mounted pipework (item 8) and buried pipework depths (item 21); use Table 5 for the latter.