Almost all of the damage from a burst pipe happens after the water has stopped. The flood is dramatic and brief. The plaster, the floor, the joists and the insulation then stay wet for weeks, and that is what decides whether you end up with a repair or with a mould problem that outlives the pipe by years.
So this page is a third about stopping it and two thirds about drying.
The order that matters
Step two is the one people skip and it is not optional. Closing the stop tap stops more water arriving. It does nothing about the water already standing in every pipe in the building, and in a two storey house that is a surprising amount, all of it uphill of the hole. Opening the taps lets it out somewhere you have chosen.
A loft tank changes the arithmetic entirely. A cold water storage tank holds roughly 200 to 230 litres in a typical UK installation, it is above everything, and the stop tap does not touch it. There is normally a gate valve on the outlet pipe. If you cannot find it or it will not move, opening every tap is what empties the tank.
Turn the boiler off once the water is off. A combi firing with no water going through it, or an immersion heater running in a draining cylinder, is a way to damage an expensive appliance and in some cases worse.
Electricity and water
Anything that got wet and is plugged in stays unplugged until it has been checked, however fine it looks. That includes extension leads, which sit on floors and fill up.
Holding it until you can fix it
You may not get a plumber the same day, particularly in a cold snap when every pipe in the county has gone at once.
- A pipe repair clamp is the proper answer for a split in copper. A few pounds, keeps working for months, and worth having in the cupboard before you need it.
- Self-amalgamating tape wraps and fuses to itself, and will hold a pinhole or a weeping joint at mains pressure. Stretch it hard as you wrap and overlap by half each turn.
- Epoxy putty works on a pinhole in a dry, clean, roughened pipe. It will not work on a wet one, so you have to get the water off and the pipe dry first, which means the stop tap stays shut while it cures.
- A cut-off and cap is often the calmest option. If the burst is on a branch feeding one thing, isolating that branch lets you turn the rest of the house back on.
Drying, which is the real job
Get the water out physically first. Mop, wet vacuum, towels. Every litre you remove by hand is a litre you do not have to evaporate.
Then warmth and airflow together. Either alone is much weaker than both. Heat without ventilation just moves the water into the air and then back into the cold wall in the next room. Ventilation without heat is slow.
A dehumidifier is the single most effective tool if you have power for one. Run it in a closed room, empty it daily, and be prepared to be shocked by how much it pulls out of a wall that looks dry.
Lift what you can. Carpet and underlay off the floor; underlay is almost never worth saving. Skirting boards off, or at least drill a line of holes behind them, so the wall cavity can breathe.
Wet insulation comes out. Mineral wool that has been soaked does not recover, it holds water against the structure, and it weighs a great deal.
Do not close it up until it is actually dry. Not "feels dry". A cheap moisture meter costs less than one wasted redecoration, and the sequence that ruins the job is always the same: it looked fine, it got plastered, and the stain came back through in the spring.
Stopping the next one
Most UK domestic bursts are freezing, and freezing is preventable.
- Lag every pipe in an unheated space: loft, garage, outbuilding, under a suspended floor, and against an outside wall. Foam lagging is a few pounds a length.
- Lag the loft tank and its pipework, but never underneath it. The small amount of heat rising from the house below is part of what keeps it from freezing, and insulating under the tank cuts it off.
- Leave the loft hatch open in a hard frost, for the same reason.
- Keep some heat on rather than turning it off entirely when the house is empty in winter. A low background temperature costs far less than a burst.
- Fix dripping outside taps and isolate them for winter if you can.
- Know where the stop tap is and that it turns. See the mains shut-offs, which is the page this one depends on.