Gas fitting: cost of pipework per linear metre 2026, valves and inspection

Gas pipework and gas appliances are safety-critical installations. Only a qualified, registered gas engineer, working for a business authorised for that type of work, may install, repair, alter or inspect them. This applies to jobs that look minor too: extending a pipe by half a metre, swapping a shut-off valve or moving the cooker connection a little further along the worktop.

Why so strict? You cannot "tighten a gas leak later" the way you would a dripping tap. Natural gas mixed with air can explode even at low concentrations. A badly connected or badly adjusted appliance can also produce carbon monoxide, which you can neither see nor smell. So as a homeowner, leave alone anything on a gas installation that would mean undoing a joint, taking a part off or cutting into the pipework.

In practice it often happens that, during a kitchen or bathroom refit, a helper "just moves" the gas connection and the gas engineer only turns up for the final check. A registered engineer will not sign off someone else's unauthorised work, so the pipework has to be redone. It works out cheaper to bring the gas engineer in at the start, while you are still deciding where the appliances will go.

Gas reaches your home through the distribution network and a service pipe that ends at the main emergency control valve. After that come the pressure regulator and the gas meter. The meter belongs to the network or metering operator and carries a seal. If someone breaks the seal or moves the meter themselves, that counts as unauthorised interference, and the operator treats it as a serious breach of the supply terms. If you want the meter or its box moved, agree it with the gas distributor first.

Everything after the meter is your installation: the pipework in the house or flat right up to the appliances. As the owner, you are responsible for keeping it safe and having it checked regularly. If you let a property, local rules often place extra duties on you as a landlord, such as yearly safety checks, so look up what applies where you live.

In a block of flats it gets more complicated. Risers and shared pipework are common parts of the building, so you may only work on them with the consent of the building management or the owners' association. The building management usually arranges periodic checks of the whole building too. When that happens, you need to let the engineer into your flat, otherwise the inspection is incomplete.

A new gas connection, a change in supply capacity or a larger alteration to the pipework usually needs a proper gas installation design. Whether your work needs notification, approval or nothing at all depends on local building regulations. Check with the local building authority and with the gas distributor before anything starts, and do not assume that a quick notification will be enough.

The traditional material for pipework inside the home is steel pipe joined by welding. A weld cannot be taken apart, and when it is done well it is very reliable. That is why welded steel is still used mainly in wall chases and on longer runs.

A common alternative is copper joined by brazing, also called hard soldering. The soft soldering you may know from water pipes is not used on gas. Press-fit systems in steel, copper or stainless steel go in quickly and without a naked flame. However, only fittings and seals expressly approved for gas may be used. Manufacturers mark them, often with a yellow stripe or a symbol. A water fitting and a gas fitting can look almost identical, and mixing them up is a serious mistake.

Underground pipework outside the house uses polyethylene pipe made for gas, usually yellow. It sits in a sand bed at the depth set in the design, typically around 0.8 m, with yellow warning tape laid above it. Where the pipe comes out of the ground into the building, a PE-to-steel transition fitting is used, and the pipe passes through the wall in a sleeve.

The route should be short and easy to follow. Only permanent joints may disappear into a chase under plaster: welds, brazed joints or press-fit joints approved for concealment. Joints that can be undone, such as the threaded connection of a valve, must stay accessible. So never plaster over a shut-off valve or hide it behind fixed boarding or tiling without an access panel.

Gas pipework must keep the required distance from electrical cables, water pipes and drains, and must never be used as an earth. Where it passes through a wall or floor, it goes in a sleeve so that movement in the structure cannot damage it. Gas pipes only go inside plasterboard partitions, into unventilated shafts or under floors you cannot inspect if the design and the relevant EN standards and local regulations expressly allow it.

Exposed pipework is painted yellow or labelled so that anyone can see straight away what it carries. When someone drills into that wall a few years later, it saves them time and trouble.

A tightness test shows whether the pipework is sealed, before it is covered up and before any appliances are connected. The engineer pressurises the pipework with air or an inert gas to the test pressure and watches whether the pressure drops over the required period. The result goes into a test certificate, which forms part of the commissioning documents.

The inspection and commissioning record confirms that the installation was safe and met the rules on the day it was checked. It is not a permanent guarantee. If you replace an appliance or the pipework is altered after the inspection, it needs checking again.

Besides the first check before the gas goes on, the installation needs periodic inspections. How often depends on local regulations and the type of property, with rented homes often under stricter rules. You will usually find the next due date on the latest record. Your boiler also needs its own service as the manufacturer specifies, often once a year, and the warranty usually depends on it.

Since September 2015, EU ecodesign requirements have practically pushed conventional non-condensing boilers off the market. When you replace an old boiler, you will almost always get a condensing one. That brings a few changes that are easy to forget when planning.

• Flue: a condensing boiler produces cool, damp flue gases. An old masonry chimney cannot cope with them, so it is lined with a plastic or stainless steel liner rated for condensing use, or a concentric balanced flue is fitted instead.
• Condensate: the boiler produces acidic water that drains through a trap into the waste system. You therefore need a drain close to the boiler.
• Flue check: before the boiler is started, the flue is checked and a record issued. For gas appliances the flue check is then usually repeated once a year, or at whatever interval local rules set.
• First start-up: the installer or the manufacturer's authorised service does this. They set up combustion and record the commissioning.

For hot water from gas there are two options. A gas-fired storage water heater connects directly to the gas supply and has its own flue. An indirectly heated cylinder does not connect to gas at all: water from the boiler heats it through a coil, and fitting it is a job for a heating engineer and plumber.

A cooker or hob connects to the pipework either rigidly or with an approved flexible hose, and there must be an isolation valve in front of it. Only a registered gas engineer may connect or disconnect the appliance, and they check tightness and correct operation at the same time. Swapping the hose yourself when moving house or fitting a new kitchen is a typical risky job in homes, and people tend to underestimate it.

Flexible hoses do not last for ever. You will find the production or expiry date printed on the hose. Rubber hoses need replacing sooner, usually after a few years, while stainless steel corrugated hoses last longer. The hose must not run behind the oven or over a hot surface, and it must not be stretched, kinked or trapped by a drawer.

Newer hobs have a flame failure device on every burner: if the flame goes out, it shuts off the gas. On an old cooker without one, a pan of milk boiling over is enough to put the flame out while gas keeps flowing. That alone is a good practical reason to replace an old cooker.

Natural gas is lighter than air and rises to the ceiling, so its detector goes high up, usually just below the ceiling. LPG from cylinders, a propane and butane mix, is heavier than air and gathers near the floor, so its detector goes low down. If you switch from bottled gas to mains gas, the detector has to be moved or replaced.

A gas leak detector does not replace a carbon monoxide alarm. Carbon monoxide forms when fuel burns incompletely, for example when the flue is blocked or there is not enough air, and no gas has to be leaking at all. In a room with a boiler or an instantaneous water heater that has an open combustion chamber, a CO alarm is a sensible safeguard. Detector sensors have a limited life, which the manufacturer states on the label.

Boilers and water heaters that take their air from the room need a permanent air supply. If you replace old windows with airtight uPVC ones without trickle vents, or fit a powerful cooker hood that extracts outside, the air pressure in your home can change. Flue gases may then spill back into the room.

Natural gas has no smell of its own. The distributor adds an odorant so you notice a leak before it reaches a dangerous level. If you smell gas, follow these rules:

• Do not use naked flames, do not smoke and do not light any appliances
• Do not switch lights or electrical appliances on or off, do not pull out plugs and do not ring neighbours' doorbells, because a spark in a switch can ignite the mixture
• Open windows and doors and, if it is safe, turn off the gas at the main emergency control valve
• Leave the building and warn others by knocking and calling out
• Once you are outside in a safe place, call the gas emergency line (the number is usually on the meter or your gas bill) or the emergency number 112

Never look for a leak with a flame or a lighter. If the smell is faint, only near the cooker, and goes away once you close the cooker valve, do not use the cooker until a registered gas engineer has checked it.

In this guide you take nothing apart and do not touch the pipework or any joints. It is a regular check any flat or house owner can manage, and it helps you spot in good time when to call a gas engineer.

1. Find the main emergency control valve and the cooker isolation valve, and make sure nothing blocks access to them.
2. Dig out the latest inspection record and check when the next inspection is due.
3. With the cooker cold and the valve closed, look over the connection hose, check its expiry date and make sure it is not cracked, kinked, stretched or running over a hot spot.
4. Remove the burner caps and flame spreaders, wash them in warm water with washing-up liquid as the manufacturer recommends, and let them dry completely.
5. Put the parts back exactly where they belong, light the burner and check the flame: it should be blue, steady and even all the way round.
6. Press the test button on the gas detector and the CO alarm, and check the sensor's expiry date.
7. Make sure the vents and grilles in the room with the appliance are not covered or taped over.
8. Note any yellow or sooty flame, a flame lifting off the burner, a damaged or expired hose or an overdue inspection, and book a registered gas engineer.

• Proof of the gas engineer's qualification and registration, and of the business's authorisation
• Tightness test certificate issued before the pipework was covered
• Inspection and commissioning record with a satisfactory result and the date of the next inspection
• Flue inspection record for any appliance with a flue
• Record of the boiler's commissioning by the installer or authorised service
• Main valve and appliance valves accessible, labelled and working
• Exposed pipework painted or labelled, chases closed only after testing
• Appliance hoses approved for gas, with a legible date
• Detectors positioned for the type of gas and working
• A sketch of the pipe route in the walls for future alterations