Leak Detection, Testing, Repair and Maintenance
Test methods
- Hydraulic pressure test on supply lines: plug all outlets, fill, expel air, raise to about 1.5 times working pressure with a hand test pump (commonly around 10 bar for domestic lines), hold one hour, and record the gauge reading. No drop means pass.
- Drainage: water test - plug the low end, fill the section to a head of about 1 m above its highest point and hold 30 minutes; air or smoke test for stacks, where smoke reveals open joints and missing traps.
- Meter test: close every tap and appliance and watch the water meter; a moving meter means a leak on the live side.
Locating a leak
Isolate zones with valves to narrow the fault, then listen with a listening stick, look for damp patches and salt marks, feel for warm patches on hot lines, and drop dye into a cistern to check a WC leak. Open a wall only after the zone is isolated and confirmed.
Repairs
- Replace the washer or jumper in a bib cock; replace the O-ring in a quarter-turn ceramic valve.
- Compression joint leaking: renew the olive rather than tightening harder.
- GI pin-hole: cut out the section and fit a new length with two couplings and fresh threads; epoxy putty is temporary only.
- Failed solvent-welded joint: cut it out and remake with two couplings - cement will not rebond a failed joint.
- OHT float valve: renew washer or the whole valve, and check the overflow.
Worked example. A damp patch appears under a first-floor bathroom. Close the main stop cock; if the meter still moves, the leak is on the pressurised side. Re-pressurise zone by zone, isolating the WC and basin lines in turn; the zone that loses pressure holds the leak, and only that wall is opened.
Traps that cost marks
Using an air test on a supply line instead of water (stored energy, masks leaks); testing before solvent cure; over-tightening compression nuts; ignoring a seeping overflow. Maintenance: descale aerators, exercise valves, clean the sump annually.