Stop pipes knocking and banging — HomeGraft

Work out why your pipes bang or knock, then trace and re-fix the loose clip safely, whatever your wall or ceiling type.

SP-01Listen and work out the type of noiseA single bang when a tap or washing machine valve shuts off is usually water hammer. A rattling or knocking noise as the heating warms up or cools down is usually a pipe rubbing against a loose clip or joist. Note when the noise happens and which room it's loudest in before you do anything else, as this tells you where to look.

SP-02Find your stopcock and check it turnsBefore you touch any pipework, find your main stopcock — usually under the kitchen sink — and turn it a quarter turn to check it moves freely. You may need to shut the water off quickly if you disturb a joint while working. Don't skip this even if you don't expect to need it.

SP-03Rule out trapped airTrapped air can cause banging in radiators and pipes. Bleed each radiator with a radiator key until water flows steadily with no hissing, and run each tap in the house for 20 seconds to clear air from the supply pipes. If the noise stops here, you're done.

1 each · Radiator bleed key

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SP-04Check a worn tap washer or valveIf the bang happens the instant a tap is turned off, the washer inside that tap or the washing machine's inlet valve may be worn, letting water slam shut. Turn off the isolation valve under the tap, undo the tap head, and check the washer for wear or splitting. Fit a new washer if it's flattened or cracked.

1 each · Tap washer (assorted sizes)

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1 roll · PTFE tape

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SP-05Check the loft tank ballcock if you have oneIf you have a cold water tank in the loft, a worn or badly adjusted ballcock valve can bang as it closes. Lift the float arm gently — if the noise matches, the washer inside the valve needs replacing, or the arm needs adjusting so it closes more gently. Leave this to a plumber if the tank is hard to access safely.

1 each · Ballcock washer kit

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SP-06Trace the pipe run and find the loose clipFollow the noisy pipe from where it's visible — under floorboards, in a cupboard, or along a wall — and gently push or wobble it by hand every 300-500mm. A clip that's cracked, missing, or not gripping the pipe tightly is usually the culprit. Mark the spot with masking tape so you can find it again.

1 roll · Masking tape

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SP-07Work out what's behind the wall or ceiling before drillingCables and pipes can run almost anywhere, not just in the usual safe zones, so always use a cable and pipe detector before drilling — then still assume something might be there and check as you go. Detectors miss cables that are deep, in metal conduit, behind metal-backed plasterboard, or outside the usual routes, and a metal stud frame can confuse cheap detectors further. If there's any doubt, isolate the circuit at the consumer unit before drilling, and make sure your stopcock (from step SP-02) is ready to turn off if you nick a pipe.

1 each · Cable and pipe detector

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SP-08Work out timber stud, metal stud, or solid wallRun a magnet or stud detector along the wall or ceiling: a steady line of hits every 300-600mm following screw heads usually means timber studs or joists. A dull, even hollow sound with no magnet hits often means metal studs. Drill a small 3mm pilot hole in an inconspicuous spot — timber dust means wood, fine grey swarf means metal, and solid resistance with brick-coloured dust means masonry.

1 each · Stud detector or magnet

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1 each · 3mm drill bit

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SP-09Re-fix the pipe clip with the right fixing for your wall or ceilingInto a timber joist or stud: use a wood screw straight into the centre of the timber, no plug needed. Into a metal stud: use a self-drilling metal-stud screw or a small toggle fixing — never a plain wall plug or an ordinary wood screw, as it will strip straight through 0.5mm steel. Into solid brick or block: drill a 6mm hole to 30mm deep, insert a plastic wall plug, then screw in. Behind dot-and-dab plasterboard: use a fixing at least 60-75mm long so it bites into the masonry behind, not just the plasterboard. Into lath and plaster: locate the timber lath behind with a pilot hole and screw into that, or use a spring toggle if you can only find plaster, and don't overtighten as old plaster crumbles.

1 each · Pipe clip (15mm or 22mm)

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2 each · Wood screws 32mm

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2 each · Self-drilling metal-stud screws

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1 each · Spring toggle fixing

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2 each · Red masonry wall plugs (6mm)

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2 each · Long masonry screw fixing 75mm

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SP-10Add foam lagging where the pipe touches anything solidSlip foam pipe insulation over the section that passes through or rests against the clip, joist, or wall. This stops the pipe rattling against hard surfaces as it expands and contracts with temperature, even if a clip loosens again in future. Cut it to length with scissors or a craft knife and push it fully over the pipe.

1 each · Foam pipe insulation (1m length)

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SP-11Turn the water back on and testOpen the stopcock fully, run the taps you tested earlier, and turn the heating on for a full cycle. Listen at the spot you fixed for at least 10 minutes, checking there's no dripping at the clip or any nearby joints you disturbed. Clear away tools, dust, and offcuts, and vacuum up any masonry or plaster dust.

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