Replace a section of damaged pipe — HomeGraft

Cut out a damaged pipe section, fit a new length safely, and reconnect without leaks in one session.

PL-01Check the damage and plan accessLook at the damaged pipe and decide how much you need to cut out — usually 150-300mm either side of the split or corrosion, so you have clean pipe to join to. Work out whether the pipe is exposed (under a sink, in a loft) or hidden behind plasterboard, masonry, or old lath and plaster. If it's hidden, you'll need to open the wall or ceiling before you can start.

PL-02Isolate the water supplyTurn off the stopcock and open the nearest tap to drain the section you're working on. Hold a bucket and old towel under the damaged pipe as you drain it, since water sits in the lowest points. Confirm the flow has actually stopped before you cut anything.

1 each · Bucket

Buy:ScrewfixB&QToolstationAmazon

1 each · Old towel or rag

Buy:ScrewfixB&QToolstationAmazon

PL-03Check for cables and pipes before you cut into the wallIf the pipe run is hidden, you'll be drilling, cutting or chasing into a wall or ceiling — cables and other pipes can run almost anywhere, not just in the 'safe zones'. Use a cable and pipe detector, then still treat the area as live: detectors miss deep cables, cables in metal conduit, anything behind metal-backed plasterboard, and metal stud frames confuse cheap detectors. Before you drill, find your stopcock (usually under the kitchen sink) and check it turns freely, so you can shut water off fast if you hit another pipe. If there's any doubt, isolate the relevant circuit at the consumer unit before drilling, and make sure the water is off at the stopcock before you cut in.

1 each · Cable and pipe detector

Buy:ScrewfixB&QToolstationAmazon

PL-04Work out what kind of wall or ceiling you're openingTap the surface. A dull, solid sound with no give is solid brick or block. A hollow sound with a regular pattern of screw heads under the paint is a stud wall — run a magnet or stud detector along it to find the studs. A hollow sound with no clear screw pattern and a slightly springy feel is often dot-and-dab plasterboard, fixed to masonry with adhesive blobs behind a 25-50mm air gap. Old, uneven, slightly bouncy walls or ceilings in pre-1930s houses are usually lath and plaster — narrow timber strips under lime plaster. A small pilot hole tells you more: fine pale dust means timber or plasterboard, grey dust means masonry, and bright metal swarf means a metal stud.

PL-05Open up the wall or ceiling to expose the pipeOn solid brick or block, chase out a channel with a hammer and bolster or an angle grinder with a diamond blade, wide enough to get pipe cutters around the pipe. On timber or metal stud plasterboard, cut a rectangle between the studs with a plasterboard saw — metal studs often have pre-punched holes the pipe already runs through, so cut carefully to avoid the sharp edges. On dot-and-dab, cut the board back to the nearest stud line or bead; the pipe is usually sitting in the void behind, not set into the masonry. On lath and plaster, expect the plaster to crumble beyond your cut line — support the edges with masking tape first and cut back to the nearest joist or batten. Keep the offcut if it's in good condition, for patching later.

1 each · Plasterboard saw

Buy:ScrewfixB&QToolstationAmazon

1 set · Bolster chisel and club hammer

Buy:ScrewfixB&QToolstationAmazon

1 each · Angle grinder with diamond blade

Buy:ScrewfixB&QToolstationAmazon

1 each · Dust sheet

Buy:ScrewfixB&QToolstationAmazon

PL-06Cut out the damaged sectionMark clean, undamaged pipe on both sides of the problem area. Cut squarely with a pipe cutter for copper or a pipe slice for plastic — a square cut matters for a good joint. Deburr the cut ends with a file or the cutter's built-in reamer.

1 each · Pipe cutter

Buy:ScrewfixB&QToolstationAmazon

1 each · Half-round file

Buy:ScrewfixB&QToolstationAmazon

PL-07Cut and fit the replacement sectionMeasure the gap and cut a new length of pipe to match, allowing for how far each coupling will slide onto the pipe. Fit slip couplings or compression fittings at each end using your usual joint method, checking the pipe seats fully home before tightening. Give every joint a firm check by hand once fitted.

0.5 m · Copper or plastic pipe, 15mm

Buy:ScrewfixB&QToolstationAmazon

2 each · Slip or compression couplings

Buy:ScrewfixB&QToolstationAmazon

1 roll · PTFE tape

Buy:ScrewfixB&QToolstationAmazon

PL-08Support the pipe with clips — fixing depends on what's behind itInto a timber stud, screw the pipe clip's back plate directly into the centre of the stud with a wood screw — never rely on the plasterboard alone. Into a metal stud, use a self-drilling metal-stud screw or a snap-fit clip made for metal track; an ordinary wood screw or a plastic wall plug will strip straight through 0.5mm steel and won't hold. Into plasterboard between studs with no stud to hand, use a small toggle or hollow-wall anchor rated for the clip's load — pipe clips are light, but the anchor still needs to grip the board properly. Into solid masonry, drill to the plug's stated depth and diameter (typically 6mm for a light clip) and fit a matching plug and screw. Behind dot-and-dab, use a fixing long enough to pass through the plasterboard and the adhesive void and bite into the masonry behind — usually 60-75mm. Into lath and plaster, fix to a joist or batten wherever you can reach one; if you must fix into the plaster itself, use a proper hollow-wall fixing rated for crumbly, uneven material, not a plain wall plug.

2 each · Pipe clips, 15mm

Buy:ScrewfixB&QToolstationAmazon

4 each · Wood screws, 40mm

Buy:ScrewfixB&QToolstationAmazon

4 each · Self-drilling metal-stud screws

Buy:ScrewfixB&QToolstationAmazon

4 each · Rawlplugs, 6mm

Buy:ScrewfixB&QToolstationAmazon

2 each · Hollow-wall toggle fixings

Buy:ScrewfixB&QToolstationAmazon

2 each · Long fixings for dot-and-dab, 75mm

Buy:ScrewfixB&QToolstationAmazon

PL-09Turn the water back on and check for leaksClose the tap you opened earlier, then open the stopcock slowly rather than all at once. Watch every joint closely as the pipe fills and pressurises. Run the tap for a minute to clear air, then check again.

PL-10Leave it and check again before closing upLeave the joints exposed for 20-30 minutes and check them again, including underneath where drips aren't obvious straight away. Dry the pipe with a cloth first so a new leak shows up clearly. Don't board or plaster over anything until you're confident it's dry.

PL-11Make good the wall or ceilingOn masonry, fill the chase with mortar or a deep-fill plaster repair and leave it to cure before decorating. On stud walls, screw your plasterboard offcut back in place (or a new patch) and finish with joint tape and filler. On lath and plaster, a plasterboard patch fixed to the exposed joist or batten is more reliable than trying to repair the original lime plaster. Leave any filler to dry fully before sanding and painting.

1 each · Plasterboard patch

Buy:ScrewfixB&QToolstationAmazon

1 set · Jointing tape and filler

Buy:ScrewfixB&QToolstationAmazon

1 bag · Ready-mixed mortar

Buy:ScrewfixB&QToolstationAmazon

PL-12Clean upDispose of the old pipe section and any plaster or masonry debris. Wipe down tools and the work area, and do a final check under the repair once everything's dry, including after the first time the hot water runs through it.

Some links may earn us a small commission at no extra cost to you.

Save this as a project

Back to all guides