How to thaw a frozen pipe safely

Signs a pipe may be frozen

• Little or no water comes from one tap while other parts of the property still have a supply.
• An exposed pipe in a loft, garage, outbuilding or outside wall has frost, ice or a visible bulge.
• The problem started during freezing weather, especially after an outside tap or unheated section was left full of water.
• A pipe may already have split without leaking because the ice is temporarily blocking the opening.

Before you apply any warmth

• Turn off the main stop tap if it is safe and accessible. This limits the amount of water that can escape if the pipe has split.
• Open the affected cold tap to relieve pressure and give thawed water somewhere to flow.
• Inspect the accessible pipe for cracks, bulges and displaced joints. Do not begin thawing if the pipe is damaged or close to unsafe electrics.
• Move possessions away and be ready to catch a small amount of water, without standing beneath an unsafe ceiling or wet electrical fitting.

Use gentle, controlled warmth

Start at the end nearest the open tap and work gradually towards the frozen section. Suitable methods for a safely accessible pipe include a warm towel, a hot-water bottle filled with warm—not boiling—water, or warm air from a hairdryer used carefully and kept away from water. Stay with the pipe throughout.

• Never use a blowtorch, naked flame, heat gun or boiling water. These can damage the pipe, start a fire or turn trapped water into dangerous steam.
• Do not use electrical heating equipment where water is present or could suddenly escape.
• Do not cut into a frozen pipe or attempt to thaw a pipe hidden inside a wall, floor or ceiling.
• Stop if you see a split, leaking joint, swelling pipe or any electrical risk.

After the water begins to flow

Keep the affected tap open and restore the main supply slowly while watching the entire accessible section. Check again after a few minutes because a small split may only become visible under pressure.

If water escapes, turn the supply off again and call a plumber. If the pipe is inaccessible, repeatedly freezes or serves an outside tap, AFS can assess the cause, repair damage and improve isolation for future cold spells.