Frozen outdoor pipes — how to thaw and prevent
⚠️ Never use a gas torch or heat gun on plastic pipes or on any pipe within a wall. Do not use boiling water — the sudden thermal shock can crack copper or plastic fittings.
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Most likely cause & what to check
External pipes — outdoor taps, garden supply pipes, pipes in unheated outbuildings — are the first to freeze when temperatures drop below zero. Signs of a frozen pipe: no flow from the outdoor tap, no flow in the shed or garage, or an unusual hissing when the internal stopcock is opened.
Turn off the indoor isolating valve for the affected pipe. This isolates the frozen section and prevents a burst pipe from flooding when it thaws.
To thaw, work from the tap or outlet end back towards the house — this allows the ice to melt with an exit route. Apply a hair dryer on low heat, a warm water bottle, or pour warm (not boiling) water over lagged cloths wrapped around the pipe.
Once flow is restored, open the tap fully for 30 seconds to flush any debris. Check all compression joints and push-fit fittings for leaks — freezing can crack fittings or break the olive seal inside compression joints.
Insulate the pipe immediately once thawed. Use closed-cell foam pipe lagging (£2–£4 per metre) with self-adhesive tape at all joins. For outdoor taps, a proprietary outdoor tap cover (£5–£10) adds significant frost protection.
For the future: in October, close the indoor isolating valve to the outdoor tap and open the outside tap to drain the exposed section. Leave the outside tap open slightly over winter so residual water can drain. A garden tap with a built-in drainage cap makes this simple.
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