Preventing Frozen and Burst Pipes

When water freezes it expands, but the failure usually occurs somewhere other than the ice itself. As the plug of ice grows it traps water between itself and a closed outlet, and it is that trapped, rising pressure that splits the pipe. The split then leaks when everything thaws.

Which pipes are most at risk

• Runs in unheated spaces: roof voids, crawl spaces, garages and outbuildings.
• Pipework on external walls, particularly where insulation sits behind rather than in front of the pipe.
• Outdoor taps and the short run of pipe feeding them.
• Any run in a property left empty and unheated during cold weather.

Prevention that works

• Insulate exposed runs, giving attention to the sections that pass through the coldest spaces.
• Isolate and drain outdoor taps before hard weather, and leave the outside tap open.
• Keep some background heat on in the building during freezing periods rather than turning heating fully off.
• Open cupboard doors under sinks on external walls so room air can reach the pipework.
• In severe conditions, a slight trickle from a far tap keeps water moving and relieves pressure build-up.

If a property will be empty

For extended absences in cold climates, isolating the supply and draining the system removes the risk entirely. Where that is impractical, background heating plus a means of remote temperature monitoring is the pragmatic alternative.

If a pipe has already frozen

A tap that gives nothing while others work normally suggests a frozen section. Close the main isolation valve before thawing, because a split will only reveal itself once flow returns. Thaw gently with warm air or warm cloths, working from the tap end back toward the frozen section. Never use a naked flame.

If a pipe has already split, keep the water off and arrange the repair before restoring supply.