Why Pipe Insulation Matters
When temperatures drop, water inside exposed pipes can freeze. As water freezes, it expands — and that expansion puts enormous pressure on pipe walls, often causing them to crack or burst. When the ice thaws, the result is a leak that can flood your home in minutes.
Pipe insulation (also called lagging) is a simple, low-cost preventative measure that every homeowner should consider, particularly for pipes in unheated spaces.
Which Pipes Are at Risk?
Prioritise insulating pipes in the following locations:
- Loft and attic spaces
- Garages and outbuildings
- Under suspended timber floors
- Pipes on exterior walls
- Pipes in unheated cupboards or utility rooms
- Outdoor taps and the pipes leading to them
Types of Pipe Insulation
| Type | Best For | Notes |
|---|---|---|
| Foam lagging tubes | Standard copper and plastic pipes | Most common, easy to fit, cheap |
| Mineral wool wrap | Larger diameter pipes and awkward runs | Good for tight spaces |
| Flexible foam wrap | Bends and irregular shapes | Self-adhesive options available |
| Pipe heating cables | Extreme cold or high-risk areas | Electric, plugs in — more expensive to run |
How to Insulate a Pipe with Foam Lagging
- Measure the pipe diameter to buy the correct size lagging. Most foam tubes come in 15mm, 22mm, and 28mm sizes to match standard pipe widths.
- Cut the lagging to length using scissors or a sharp craft knife. For bends, cut 45-degree mitre joints so pieces fit neatly around corners.
- Open the pre-cut slit along the length of the foam tube and snap it around the pipe.
- Seal the joins with pipe lagging tape or duct tape. Don't leave gaps — cold air exploits any opening.
- Cover end pieces and joints thoroughly. These are the most vulnerable points.
Insulating an Outdoor Tap
Outdoor taps are particularly vulnerable to freezing. In addition to insulating the pipe leading to the tap:
- Fit an outdoor tap cover (a foam cap available at garden centres and DIY stores).
- During prolonged cold snaps, turn off the indoor isolation valve for the outdoor tap and open the outside tap to drain any residual water.
What to Do If a Pipe Does Freeze
If you turn on a tap and get little or no water during cold weather, you may have a frozen pipe. Here's how to handle it safely:
- Don't use a blowtorch or open flame — this is a fire hazard and can damage pipes.
- Apply gentle heat using a hairdryer on a low setting, working from the tap end towards the frozen section.
- Wrap the pipe in warm (not boiling) wet towels and refresh them regularly.
- Keep the tap open so water can flow as the ice melts.
- Check for any cracks or leaks as the pipe thaws — call a plumber immediately if you spot any damage.
The Cost of Pipe Insulation vs. The Cost of a Burst Pipe
Foam lagging is inexpensive and widely available at DIY and hardware stores. A small roll of lagging tape and enough foam tubes to cover the most at-risk pipes in a typical home can cost very little — a fraction of the potential cost of water damage from a burst pipe. It's one of the best-value preventative home maintenance tasks you can do before winter.