Three moves stop most disasters at home: close a valve, flip a switch, turn a tap. As long as you know where they are before you need them.
ACT
You smell gas.
- Don't touch any switch, not to turn on, not to turn off. No flame, no doorbell, no phone call inside.
- Open the windows on your way, without lingering.
- Close the gas valve if it's on your way out: near the meter, a quarter turn. Handle across the pipe: closed.
- Get everyone out, and leave the door open.
- Call from outside, away from the house: the gas emergency number, or the fire service.
Water is pouring and won't stop. Close the main stop valve, often near the water meter: basement, under the sink, a utility cupboard, or a box in the ground outside. Turn it clockwise. Then cut the power if the water is reaching sockets or the fuse box.
You need to cut the power. At the fuse box, flip the main switch or the main breaker, often near the meter. Dry hands, dry feet. If the box is already in water: don't go near it, get out and call for help.
First of all, today: find all three. Label them, leave an adjustable wrench next to the gas valve if it needs one, and write down where they are in a sheet of your own, with a photo.
ADAPT
After shutting off the gas, don't turn it back on yourself. Every appliance has to be checked and relit: that's a professional's job, and the rule in many countries.
Earthquake. Only shut off the gas if you smell it or hear it hiss. Shutting it off "just in case" leaves you without heating until a technician comes by, and they'll have a thousand other houses to see.
A flood is coming. Cut the power before the water gets in, while the fuse box is still dry. Then turn nothing back on until an electrician has looked at the installation.
Fire. Cut the power if it's on your way out, never by going back in. See House fire.
The water valve is stuck. A valve that's never been turned seizes up with limescale. Work it gently, with small back-and-forth moves, and no extension on the wrench: an old valve that snaps is a leak you can no longer stop. Last resort: the valve on the street side of the meter, or the water company.
You're draining the pipes or the hot water tank. Cut the power to the water heater first: an electric element running dry burns out in minutes.
You live in a flat. The meter and the gas valve are often on the landing or in a service duct, sometimes shared by the whole building. Find the building's ones too, and who has the key.
Turning the power back on. Switch the main switch back on, then the breakers one by one. If one trips straight away, leave it off: the fault is on that circuit.
UNDERSTAND
Why no switch. A switch makes a tiny spark every time its contacts open or close, even when you turn something off. Natural gas ignites when it makes up roughly 5 to 15 % of the air: a room that smells strongly can be right in that range. A doorbell, a phone, a fridge motor kicking in make the same spark.
Why it smells. Natural gas has no smell at all. A sulphur compound that smells of rotten eggs is added on purpose, so a leak gets noticed at levels far below the ones that explode.
Why a quarter turn. A gas valve is a ball with a hole through it. The handle always lines up with the hole: along the pipe, gas flows; across it, gas is blocked. No label to read, no light needed.
Why water and power go together. Water conducts electricity. A fuse box or a power strip sitting in water can make all the water in the room live, with nothing to see. That's why you cut the power before stepping into a flooded basement, and never while standing in the water.
Why find them now. A burst pipe can release tens of litres a minute. By the time you've found the valve with a torch, the ceiling below has come down. The three places fit in three lines: it's the shortest and most useful sheet you'll ever write.