Even a small pipe leak can ruin a wall, a floor and the neighbours' ceiling within days, so act quickly. The sequence is always the same: shut off the water, find the leak, clean the area and decide how to seal it or what to replace.
The repair method depends on the pipe material, its age and the size of the damage. You can often manage it yourself, and sometimes it is simpler to replace a single fitting or section. Rusted couplings and nuts usually cause the most trouble, and that is where a penetrating lubricant helps.
What you will need
- adjustable spanner and pipe wrench
- wire brush, rags, a bucket
- pipe repair clamp, or plumbing thread or PTFE tape
- new fittings or a pipe insert (for larger damage)
- WD-40 Specialist Penetrant
- WD-40 Smart Straw with the two-position straw
Important: If water has reached sockets, wiring or the fuse box, switch off the electricity first. Only work on a hot-water pipe once it has cooled. A clamp is a temporary fix: plan to replace the section.
Step 1
Shut off the water and find the leak
In a flat, the valves on the hot and cold risers are usually next to the meters; in a house the main stopcock is at the supply entry or in an outside chamber. Close it and open a tap to release the pressure.
Trace the pipe from the wet patch. If the outside is dry but a stain on the wall keeps growing, the leak is probably in a chased-in pipe and the wall will have to be opened.
Step 2
Clean the damaged area
A seal only holds on a clean surface. Use a wire brush to remove rust, limescale and old paint for a few centimetres either side of the leak, then dry the pipe.
Internal deposits in old steel pipes are removed with compressed air or a sand and water mix, but that is a job for professionals.
Step 3
Seal a small leak
For a pinhole or crack in a metal pipe, fit a repair clamp with a rubber gasket centred exactly over the damage and tighten the screws evenly.
If a threaded joint is leaking, undo it, wind plumbing thread or PTFE tape around the thread in the direction of tightening and reassemble. On an old system with high pressure, a pressure-reducing valve helps protect the pipes.
Step 4
Replace the damaged section
If the pipe is corroded through or the crack is long, it is better to replace the section or fitting. The main obstacle is rusted nuts, couplings and unions that will not shift even with a long wrench.
Apply WD-40 Specialist Penetrant to the thread and give it 10-15 minutes to work under the rust. In tight spaces behind pipes, WD-40 Smart Straw is handy: the straw delivers the spray right onto the nut. Then undo it with a pipe wrench while holding the adjoining part with a second wrench so the pipe does not twist.
Step 5
Turn the water back on and check
Open the valve gradually rather than straight to full pressure. Wipe the repair dry and watch it for a few minutes: there should be no drips or damp.
If it stays dry, open the valve fully. Also check nearby joints and the riser: after a pressure change an old system sometimes starts leaking somewhere else.
Tip: Once a year, turn the ball valves on the risers through their full travel and treat the handles and nuts with
WD-40 Multi-Use. A valve that has not moved for years often refuses to turn just when there is an emergency.
What next
Inspect exposed pipes in the bathroom and kitchen every season, especially before winter in a house where unheated sections can freeze. Keep WD-40 Specialist Penetrant next to your plumbing wrenches so a seized nut never holds up an emergency repair.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
More guides in «How to use».