Installing gas pipework: clip distances, joints, sleeves and routes

Installation pipework has to be sized, supported, protected, sound and tested tight. Most of the rules below guard against the same failure: a joint that is strained, hidden or leaking into an enclosed space, where a small escape can build up unnoticed.

Supports

Clips stop the pipe sagging and keep bending loads off the joints. Sag, knocks and vibration work joints loose over the years, so support is leak prevention, not tidiness.

• Secure both ends of every run, then clip in between at no more than these spacings.
• Copper up to 15 mm: 1.5 m run horizontally, 2.0 m run vertically.
• Copper 22 mm and 28 mm: 2.0 m horizontally, 2.5 m vertically.
• Mild steel DN15: 2.0 m horizontally, 2.5 m vertically. DN20 and DN25: 2.5 m and 3.0 m.
• A vertical run can be clipped further apart because its weight hangs along the pipe instead of bending it.
• Fix clips to something solid, and keep the pipe off surfaces that could corrode it.

Joints

• The threads alone do not seal. Use a jointing compound or PTFE tape made for gas and conforming to the relevant part of BS EN 751: part 1 anaerobic compounds, part 2 non-hardening compounds, part 3 PTFE tape.
• Apply the sealant as its instructions say, and never make a threaded joint up dry.
• A compression joint seals at the olive, not the thread. Make it up to the fitting maker's instructions and never wrap tape round the olive.

Through walls and floors

A pipe through a solid wall or floor takes the shortest practicable route, inside a sleeve. The sleeve protects the pipe from movement in the structure and, if the pipe leaks within the wall, leads the gas out instead of letting it spread into the building.

• Use a sleeve of a material that can contain gas, such as copper, steel, PE or PVC, through the full thickness of the wall or floor.
• Bed the outside of the sleeve into the structure at each end with building material such as mortar.
• Seal the gap between pipe and sleeve at one end only, with a flexible fire-resistant sealant. Through an outside wall, seal the inside end so any leak vents outdoors.
• Keep joints out of sleeves: a leak starts at a joint, and inside a sleeve nobody can see or reach it.

Cavities, ducts and voids

Gas leaking into a closed space is hard to detect and can build up into an explosive mixture.

• Ordinarily, a pipe may cross a cavity wall by the shortest practicable route, suitably sleeved, but may not run along the cavity. Adding ventilation to the cavity does not remove that restriction.
• The narrow exception is the supply to a living flame effect fire that simulates a solid-fuel fire, has a fanned flue and is installed within the inner leaf. Keep the cavity section as short as reasonably practicable, enclose it in a gas-tight sleeve and seal the joint where it enters the fire.
• A shaft, duct or void that a pipe runs through must be adequately ventilated, unless the pipe is itself enclosed in a ventilated duct.

Preserve the building’s protection

Plan chases, holes and notches so the gas route does not weaken the structure. A tightness pass establishes nothing about a beam’s remaining strength. Resolve the route or obtain an appropriate structural detail before cutting.

Ventilation for a pipe duct must also preserve fire and smoke separation. Do not open a path through a compartment wall simply to vent the duct; coordinate the ventilation and fire-stopping arrangement so both protections remain effective.

Buried and embedded pipe

• Where no vehicles cross, such as under a garden, give buried pipe at least 375 mm of cover. Where vehicles cross, follow the pipe maker's figure.
• Buried or embedded metal pipe needs factory sheathing or a wrapping, because damp in the ground or structure corrodes bare metal from the outside until it leaks.
• Pipe laid in a solid floor or wall must be protected so movement of the structure cannot break it.
• Pipe running beneath foundations, wall bases or footings needs protection against movement of the structure or ground. Burial depth alone does not establish that the pipe can withstand settlement or other movement.
• Tightness-test before you wrap, paint or cover joints. A wrapped, painted or buried joint can hide its leak; paint can even seal a small leak for a while and falsify the test.

Clearance from electrics

Unless insulating material separates them, keep installation pipework at least:

• 150 mm from electricity meters and their controls, consumer units, distribution boards, switches and sockets.
• 25 mm from electricity supply and distribution cables.

A switch can spark as it operates, so the gap keeps it away from any escape at a joint, and it stops the pipe touching electrical metalwork that could corrode it.

Marking

Outside homes, for example in shops and offices, installation pipework that can be seen must be permanently marked or colour coded as gas pipe (regulation 23). Dwellings and living accommodation are exempt.

Main bonding

• Where main protective bonding is needed at an internal meter, use suitable consumer-side rigid metallic pipework before any branch, preferably within 600 mm of the outlet where practicable. The main connection is not made to the supplier’s pipe before the meter.
• With an outside meter, bond inside the building as near as practicable to where the pipe enters, before any branch, or in the meter box on the meter outlet pipe, as long as the cable does not breach the box or its sleeve seal.
• The clamp carries a label reading Safety electrical connection – do not remove.
• Whether bonding is needed is an electrical judgement: metal pipework fed by a plastic service pipe may not need it.
• If you connect pipework to a primary meter and bonding may be needed, tell the responsible person in writing that an electrically competent person should check it.