Burst pipe repair

First, stop the water

Before anything else: internal stopcock off, cold taps open downstairs, heating and hot water off. If water is anywhere near light fittings or sockets, turn off the relevant circuit. Then photograph the damage before you start mopping.

Why pipes actually burst

Freezing

Water expands by about nine per cent when it freezes, and copper has nowhere to go. A frozen section splits along its length, or a compression joint is pushed apart. The pipes that freeze are the ones in unheated space: lofts above the insulation, garages, outbuildings, crawl spaces and external walls. In practice the pipes that freeze are almost always the ones somebody ran across a loft after the insulation went in.

Corrosion

Copper pitting corrosion, usually from aggressive water chemistry or from debris sitting in a low spot. Galvanised steel, still present in plenty of older Norfolk property, corrodes from the inside until the wall thickness fails. Lead – still occasionally found on incoming supplies – fatigues and splits. Corrosion failures are gradual and almost always preceded by weeping somewhere.

Mechanical damage

A nail or screw through a pipe under a floor, a joist notched too deeply, a pipe clipped hard against a rough edge and abraded by expansion movement. The classic version of this appears weeks or months after somebody laid a new floor.

Pressure

Excessive mains pressure hammers every joint in the house. Water hammer – the bang when a valve or appliance shuts off quickly – produces pressure spikes well above the static figure. A house with very high pressure and no pressure-reducing valve will keep producing failures at its weakest joints.

The repair

Assuming the source is identified and accessible, the sequence is straightforward:

1. Isolate and drainDown to the affected section, with the system relieved so the repair is not fighting residual pressure.
2. Expose the damage properlyEnough to see the whole affected length. A split rarely stops exactly where the visible damage does, and repairing a section that is still work-hardened from freezing is a repeat visit.
3. Cut out and replaceCopper in copper, plastic in plastic, with the right fittings for the material and the location. Soldered, press or compression as the situation warrants – each has a proper place and none is universally correct.
4. Pressure test before closing upRefill slowly, check every joint, and leave it under pressure before anything is boxed back in.
5. Address the causeInsulation, re-routing, clipping, a pressure-reducing valve, or replacing a run that has corroded – whatever the actual reason was.
6. Make goodWe repair the plumbing and tidy up properly. Plaster, flooring and decorating are separate trades and we will say so rather than doing a poor job of them.

Preventing the next one

After a freeze-related burst, the useful work is not the repair. It is these:

• Insulate every pipe in unheated space. Loft pipes must be lagged and must sit *above* the loft insulation is wrong – they should be below it where possible, so they stay in the warm side. Where they cannot be, they need proper lagging with no gaps, particularly at bends and valves where the lagging is usually missing.
• Insulate the cold water tank but do not insulate underneath it – the tank benefits from warmth rising from the house below.
• Fit a drain point and isolation for any external run, so outside taps and outbuildings can be emptied before winter.
• Deal with draughts into the loft, which are what actually drives loft temperatures down to freezing.
• Keep the heating on low during cold snaps if the house is empty, or drain the system down properly if it will be empty for a long period. Turning it off completely for a fortnight in January is how second homes get destroyed.
• Fit a pressure-reducing valve if your mains pressure is high enough to be causing failures.