Why outside taps freeze and burst

Outside taps are one of the most common sources of a winter emergency callout, and almost always preventable. The pattern is nearly always the same: a cold snap freezes water sitting in the pipe, the ice expands and splits the pipe or the tap body, and the leak only becomes obvious once the thaw comes and water starts running from a crack that has been there for days.

Why it happens

Outside taps and the short run of pipe feeding them are exposed to outside temperatures in a way that indoor pipework is not, and they are also usually the last thing anyone thinks about before a freeze. Water left standing in that exposed section is what actually freezes and splits the pipe — it is very rarely the tap fitting itself that fails first.

How to stop it happening

• Disconnect and drain any hose before the first proper cold snap, since a hose left attached holds water against the tap.
• Fit an insulated tap cover, sold cheaply at most hardware shops, over the tap body itself.
• Where the supply allows it, isolate the outside tap's internal stopcock and open the outside tap to drain the short pipe run completely before winter.
• Lag any exposed pipework leading to the tap, particularly where it runs through an unheated garage or outbuilding.

If it has already happened

A burst outside tap on its own is rarely a full emergency — isolating it at the internal stopcock usually stops the leak until it can be properly repaired. But if you cannot find or reach that isolation point, or water is getting into the house rather than just the garden, that becomes an emergency plumbing callout rather than something to leave until Monday. Once it is fixed, refitting with a proper frost-proof outside tap is worth doing rather than replacing like-for-like, since a frost-proof valve sits back inside the wall where it is protected from exactly this.

A frozen or burst pipe elsewhere in the house is a job for pipe repair. If you suspect a leak you cannot see, our guide to hidden leaks and high water bills explains what to look for.