Lag hot and cold water pipes

Wrap exposed hot and cold pipework in foam lagging to stop heat loss and reduce the risk of frozen pipes.

AB-01Measure your pipes and buy the right laggingMeasure the outside diameter of each pipe with a tape measure — most UK copper pipe is 15mm or 22mm, with 28mm used for some boiler and cylinder pipework. Buy foam pipe lagging (pipe insulation tube) to match each size, plus a roll of pipe insulation tape for joints and awkward shapes. For pipes in a loft, garage or under a suspended floor, buy the thicker or weatherproof-rated lagging, since these are the pipes most likely to freeze.

6 each · Foam pipe lagging, 15mm bore x 1m

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4 each · Foam pipe lagging, 22mm bore x 1m

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1 roll · Pipe insulation self-adhesive tape

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1 each · Tape measure

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AB-02Get set up safely before you startPipe lagging is low-risk work, but if you're heading into a loft, wear gloves and old clothes — loose loft insulation is itchy and gets everywhere. Only stand on joists or proper loft boards, never on the plasterboard ceiling between them, or you risk your foot going straight through. If you're working near hot pipework, let the heating cool down first so you don't burn yourself.

1 pair · Work gloves

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1 each · Head torch or work light

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AB-03Fit lagging along straight pipe runsMost foam lagging has a slit down one side — open it up and press it over the pipe so it clips shut around it. Push each length up against the last one so there are no gaps, and cut lengths to size with a craft knife or scissors. Work along the whole visible run, including pipes tucked against walls or joists.

1 each · Craft knife or scissors

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AB-04Cover bends, corners and tee jointsAt a bend, either use a pre-formed foam elbow piece if you bought one, or mitre-cut the straight lagging at 45° so the two pieces meet neatly around the corner. At a tee joint, cut a notch into one piece so it fits snugly around the branch pipe. Wrap pipe insulation tape around every joint and cut edge so there are no gaps where cold air can reach the pipe.

4 each · Pre-formed foam pipe elbows

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1 roll · Pipe insulation self-adhesive tape

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AB-05Wrap valves, stopcocks and irregular fittingsStop taps, isolation valves and pipe fittings are awkward shapes that foam tube won't fit over. Wrap these in several layers of pipe insulation tape instead, working from one side to the other so it overlaps like a bandage. Don't cover the handle of any valve or stopcock completely — you need to still be able to find and turn it in an emergency.

1 roll · Pipe insulation self-adhesive tape

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AB-06Secure loose sections and check for gapsRun your hand along each length of lagging to check the slit has closed fully and nothing has sprung open. Add extra tape at any point where lagging meets a wall, joist or another pipe, since these are the spots most likely to work loose over time. Pay particular attention to pipes near an outside wall, loft hatch or air vent, as these are most exposed to cold air.

AB-07Clear up and do a final checkCollect all offcuts of foam and tape backing and put them in your general waste bin — pipe lagging can't be recycled with normal packaging. Do a last walk-through of every pipe run you've lagged, checking hot and cold pipes both, and confirm no bare copper is left showing. Wash your hands after handling foam insulation, as it can leave a fine residue on your skin.

1 each · Bin bags

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