If you can smell gas right now, stop reading and ring the National Gas Emergency Service on 0800 111 999. It is free, it is open all day and night, and the engineer they send will make the property safe. Do not use a light switch, a phone inside the house or anything that could spark on your way out.
This page is for what comes after that call. The emergency engineer will usually isolate the supply at the meter and leave you with no gas and a leak somewhere on your own pipework that still has to be found. We explain the safety steps, what the emergency service does and does not do, and how gas leaks in Hertfordshire and Essex are pinpointed with tracer gas and detection equipment.
What to do in the first five minutes
Open the doors and windows to let the gas out. Turn the gas off at the meter if you can reach it safely, by turning the lever a quarter turn so it sits across the pipe. Do not switch anything electrical on or off, including lights, and do not light a match or smoke. If the smell is strong, go outside before you make the call.
Ring 0800 111 999 from outside or from a neighbour's house. Tell them your address and what you can smell. If anyone feels dizzy or sick, get them into fresh air and tell the operator. Keep people and pets away from the room with the strongest smell until the engineer arrives.
If you are in a flat or a terrace, let the neighbours know. Gas moves through shared voids and under floors, and the leak may not even be in your home. Stay out until the engineer has been and says it is safe to go back in, however cold it is outside.
• Open windows and doors
• Turn the gas off at the meter
• No switches, flames or phones indoors
• Call 0800 111 999 from outside
• Tell the neighbours
What the emergency service does, and what it leaves you with
The emergency engineer's job is to make the property safe. They will test for gas, find out roughly where it is coming from, and if the leak is on your side of the meter they will normally turn the supply off at the meter, fit a warning label and tell you not to use it until the pipework has been repaired and tested.
What they do not do is find the exact point of a leak on your own pipework. The gas network's responsibility ends at the meter. Everything after it, the pipe to the boiler, the hob and the fire, belongs to the householder or landlord, and so does finding and fixing the leak on it.
If the leak is small and the pipe runs under a solid floor or inside a wall, a gas engineer without tracing equipment cannot see where it is. That is when a slow leak becomes a leak detection job rather than a plumbing one.
How a slow gas leak is found with tracer gas
Charlie isolates the suspect pipe run, which is already off at the meter, and charges it with a tracer gas, a small proportion of hydrogen in nitrogen made for leak testing. It is not flammable at that mix and it leaves no residue. Hydrogen is the smallest molecule there is, so it escapes through the same hole the gas was leaving by and rises straight up through screed, tiles and plaster.
A hand held detector is then passed along the pipe route: over the floor, up the wall and out across the garden if the pipe runs to an outbuilding. The reading climbs as the probe nears the leak and peaks directly above it. That spot is marked on the floor or wall. On a long run the whole route is walked so a second leak is not missed.
Where the pipe route is not known, it is traced first. A thermal camera is useful on pipework that runs alongside heating pipes, and a pressure gauge on the isolated run confirms the leak is real and gives a sense of its size before any tracer gas is used.
The job ends with a written report giving the location, the method and photographs. Your gas engineer then opens the floor or wall at the marked point, repairs the pipe and tests the system before the supply goes back on. We find the leak. The repair and the recommissioning are for a registered gas engineer.
Where gas pipes leak in Hertfordshire and Essex houses
In the 1950s to 1970s houses that make up so much of Stevenage, Welwyn Garden City, Harlow and Basildon, the gas pipe to the kitchen and the gas fire often runs in the concrete floor. Steel pipe in screed corrodes from the outside, and the first sign is a faint smell near the skirting that comes and goes.
In the older terraces of Hertford, Ware and Colchester the pipe runs under suspended timber floors and through walls, with joints where the house was converted or extended. Each joint is a place for a slow weep. Pipes to garden rooms and outbuildings, buried without the right protection, are a growing source of callouts.
Flats are the hardest, because a smell in one home can come from a pipe in another, or from a riser in a shared duct. The tracer gas method works there too, because it tests one isolated run at a time.
The cost of leaving it
A gas leak that has been made safe at the meter means no heating, no hot water and no cooking until it is found and repaired. Every day the pipe stays unfound is a day of that. A slow leak that has not yet been reported is worse, because gas can collect in a floor void or under a kitchen unit with nowhere to go.
Some people try to find it by lifting boards or chasing the pipe along the wall. Each opening is repair work later, and most leaks are not where the smell is strongest. Pinpointing first and opening once is cheaper and quicker, which is also the argument an insurer will accept.
Getting a visit in Hertfordshire or Essex
Ring 07897 020 680 once the emergency service has been and the supply is off. Charlie covers Hertfordshire and Essex from Haverhill in Suffolk, about 45 miles from Hertford and 40 from Maldon, and can usually book you in within 24 to 48 hours. Say on the phone that the gas is off, so the visit is booked as early as the diary allows.
We have found leaks for customers in Bengeo and Hertford Heath in Hertford, Codicote and Graveley near Stevenage, Bocking in Braintree, Hockley, and Pitsea in Basildon. The visit runs on no find, no fee, and you get the written report your gas engineer and insurer both need.
Questions people ask
I can smell gas now. Should I ring you?
No. Ring the National Gas Emergency Service on 0800 111 999 first, open the windows, turn the gas off at the meter and go outside. They make the property safe. Ring us afterwards if the leak is on your own pipework and has not been pinpointed. We find leaks that have already been made safe; we are not an emergency gas service.
Do you repair the gas pipe as well?
We find the leak and mark it. Repairing gas pipework and putting the supply back on must be done by a registered gas engineer, who will also test the system afterwards. The report from the leak detection visit tells that engineer exactly where to open up, so the repair is one hole rather than a search.
Can the tracer gas be used while we are living in the house?
Yes. It is a mix of a small amount of hydrogen in nitrogen, made for leak testing, and at that proportion it will not burn. It is used in an isolated pipe run, not released into the room, and the small amount that escapes at the leak rises and disperses. The house can stay occupied during the survey.
Can you find a gas leak under a concrete floor in Welwyn Garden City or Stevenage?
Yes. That is the typical job in those towns, where the pipe to the kitchen or fire was laid in the screed. Tracer gas rises through concrete and tiles, and the detector reads it at the surface directly above the leak. The floor is opened at that one point. The same applies to the older terraces in Hertford and Ware.