Gas Leak London
Smell gas? Act now — don't touch switches. Get out, open windows, call 0800 111 999 (National Gas Emergency), then call us. We carry out trace, repair, and tightness testing across London — Gas Safe registered.
🚨 IF YOU SMELL GAS RIGHT NOW — DO THIS IMMEDIATELY
Don't operate any switches
Don't turn lights, appliances, or electrical switches on or off — a spark can ignite gas. Don't use your mobile phone inside the property.
Open all windows and doors
Ventilate the property immediately to disperse any gas that has accumulated. Do not use extractor fans (electrical).
Get everyone out
Leave the property. Close the front door behind you but do not lock it — you may need emergency access.
Call the National Gas Emergency line
Call 0800 111 999 from outside your property. Free, 24/7. They will attend within 1 hour. Do not re-enter until they clear the property.
Call us after the emergency team leaves
National Grid will isolate the gas but will not make permanent repairs. Call us to carry out the full trace, repair, tightness test, and reinstatement.
- Turn any electrical switches on or off
- Use your mobile phone inside the property
- Light a match, candle, or cigarette
- Turn the boiler on or off
- Use any electrical appliances (including extractor fans)
- Try to trace the leak yourself
- Re-enter the property until the emergency service clears it
Where Do Gas Leaks Come From?
The most common gas leak sources in London properties — ranked by frequency. Our engineers use electronic gas sniffers to pinpoint the exact source before any repair.
Gas meter connections
High riskThe union connections on either side of the gas meter are common failure points — particularly on older meters or those that have been recently replaced. A small leak here can accumulate in an enclosed meter cupboard.
Signs: Smell near meter cupboard. Whistling or hissing sound from meter area.
Flexible gas connectors (cooker / hob)
High riskThe flexible corrugated connector between the gas supply pipe and a cooker or hob deteriorates over time. Cracks in the outer sheath allow gas to escape. These have a 10-year recommended service life.
Signs: Smell near the cooker when all burners are off. Connector visually cracked or kinked.
Boiler gas valve or burner
Medium riskA faulty gas valve or worn burner seal can allow small gas escapes inside the boiler casing. These are only detectable with electronic sniffers — not reliably by smell.
Signs: Boiler error codes. Pilot light going out. Smell near boiler flue.
Underground service pipe
Medium riskThe gas service pipe running from the pavement to the meter can corrode or suffer ground movement damage. Older properties (pre-1970) may have iron mains pipes which are being progressively replaced by National Grid.
Signs: Dead patches of grass along the pipe route. Persistent smell in the street. Bubbles in puddles.
Internal gas pipework joints
Low–Medium riskPush-fit or compression fittings on internal gas pipework can work loose over time, particularly after nearby building work that has caused vibration. All gas pipework must be tested after any building work in the property.
Signs: Smell in specific room not related to appliances. Smell after recent renovation work.
Unused gas points (capped pipes)
Low riskOld gas outlets for removed fires or appliances should be properly capped. Removed appliances sometimes have their supply turned off at the isolation valve but not properly capped — a valve alone is not a permanent seal.
Signs: Smell in a room where a gas fire or appliance was previously fitted.
Gas Leak Repair Prices — London 2026
| Job | Typical time | Price |
|---|---|---|
| Emergency gas isolation (National Grid called — cap not our scope) | N/A | Free via 0800 111 999 |
| Gas tightness test (after isolation or post-renovation) | 45–60 min | £85–£120 |
| Trace and repair — minor leak (joint, flexible connector) | 45–90 min | £120–£180 inc. parts |
| Flexible gas connector replacement (cooker / hob) | 30–45 min | £75–£110 inc. parts |
| Gas pipe section replacement (internal) | 1–2 hrs | £150–£350 inc. parts |
| Gas meter connection repair | 45–60 min | £120–£180 inc. parts |
| Gas safety certificate (CP12) after repair | 45–60 min | £80–£110 |
| Full gas installation test (post-renovation) | 60–90 min | £120–£180 |
Fixed quote before we start. No call-out fee. All repairs include a final gas tightness test. We issue a Gas Safety Record on completion.
Gas Engineers Across All London Boroughs
Gas Safe engineers on call across all 33 London boroughs. Same-day attendance.
Gas Leak FAQs
What should I do if I smell gas in London?
Act immediately: don't turn any switches on or off. Open all windows and doors. Get everyone out. Call the National Gas Emergency line (0800 111 999) from outside — free, 24/7. Don't re-enter until National Grid attends and declares the property safe. After they leave, call us to carry out the repair and tightness test.
How much does gas leak repair cost in London?
Gas tightness testing costs £85–£120. Trace and repair of a minor gas leak (fitting joint, flexible connector) is £120–£180. Pipe section replacement is £150–£350 depending on length and access. All work is Gas Safe registered and includes a pressure test before sign-off. Fixed quote before starting.
What does a gas leak smell like?
Natural gas is odourless — suppliers add mercaptan (a sulphur compound) that gives it a distinctive 'rotten eggs' or 'rotten cabbage' smell. Even a faint smell should be treated seriously. You may also notice a hissing sound near gas pipes, dead patches of grass above underground pipes, or higher-than-expected gas bills.
Can I use a detector to find a gas leak?
Domestic gas detectors can indicate the presence of gas, but cannot pinpoint the source. We use calibrated electronic gas sniffers and pressure testing equipment that isolate a leak to a specific joint, appliance connection, or pipe section. If your detector alarm has triggered, treat it as a real emergency and call 0800 111 999.
Who can legally repair gas leaks in the UK?
Only Gas Safe registered engineers are legally permitted to work on gas appliances and gas pipework in the UK. It is illegal for anyone who is not Gas Safe registered to carry out gas work. Always check the engineer's Gas Safe ID card — you can verify registration at the Gas Safe Register website. We are Gas Safe registered.
What happens if National Grid caps my gas?
The National Gas Emergency service will isolate and cap your gas supply if they find a dangerous escape. They will not carry out permanent repairs — that is your responsibility. After they leave, call us to trace the fault, carry out the repair, conduct a full tightness test, and restore your gas supply.
Related Services
Smell Gas? Call Now.
Gas Safe registered · Same day · All 33 boroughs
Emergency gas escape: 0800 111 999 (National Grid — free, 24/7)
📞 Call 020 0000 0000