Fix a pinhole leak in a copper pipe

Isolate the water, cut out the damaged section of copper pipe, and fit a repair coupling to stop the leak.

PL-01Find the leak and set upLook for the pinhole itself — a fine spray, a drip, or green-blue staining on the copper. Dry the pipe with a cloth so you can see exactly where the hole is. Lay a dust sheet and towels underneath, and have a bucket, torch and mirror ready if the pipe is hard to see.

1 each · Dust sheet

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1 each · Bucket

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PL-02Turn off the water and drain the pipeTurn off the stopcock, usually under the kitchen sink, and check it fully shuts. Open the taps fed by that pipe, plus the highest tap in the house, to let it drain and let air in. Never cut into a copper pipe until you're sure it's empty — a pinhole leak under mains pressure can spray hard enough to hurt you.

PL-03Mark and cut out the damaged sectionMark a point about 20mm each side of the damaged spot, giving room for two couplings. Cut both marks with a pipe cutter for a clean, square cut, then remove the damaged length. Deburr the inside and outside of both cut ends with a file or the cutter's reamer.

1 each · Pipe cutter (15mm)

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1 each · Half-round file

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PL-04Clean the pipe endsClean the last 25mm of each remaining pipe end with wire wool or emery cloth until it's bright copper. This matters more for compression joints, but do it for push-fit too. Wipe away any swarf or grit before you fit anything.

1 each · Wire wool or emery cloth

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PL-05Cut the replacement pipe sectionMeasure the gap and cut a new length of 15mm copper pipe to fit, allowing for how far each end sits inside a coupling. Deburr and clean this new piece the same way as the existing ends.

1 each · 15mm copper pipe (1m length)

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PL-06Fit the repair couplingsJoin the new section to the existing pipe with two compression couplings or two push-fit couplings. For compression, slide on the nut and olive, push the pipe fully home, then tighten by hand plus one further turn with a spanner — don't overtighten. For push-fit, push each end firmly into the fitting until it stops; no tape or jointing compound needed.

RULES

2 each · 15mm compression coupling

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2 each · 15mm push-fit slip coupling (alternative)

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1 each · Adjustable spanner

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KNOW THE RULES

The Water Supply (Water Fittings) Regulations 1999 require any fitting used on a drinking water system to be suitable for that use — check it's marked as such (most UK plumbing fittings sold for domestic use are WRAS approved).

PL-07Turn the water back on and check for leaksClose the taps you opened earlier, then turn the stopcock back on slowly. Run your hand carefully along the repaired section, checking both joints closely for drips — cut pipe edges can be sharp. Leave it for 15-20 minutes and check again before you leave the area.

PL-08Recheck later and tidy upCome back after a few hours, ideally after the hot water or heating has run again, and check the joints once more — they can seep slightly under heat when they didn't under cold pressure. Dry the area, dispose of the old pipe section and used wire wool, and remove the dust sheets.

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