Maintenance, Repair, Leak Detection and Testing of Installations
What is tested
This domain covers planned and reactive maintenance, fault finding, leak location and proving an installation before handover. Expect questions on pressure testing, inspection, flushing, disinfection and the sequence for repairing a leak without contaminating the supply.
Core rules
- Preventive maintenance includes checking supports, valves, traps, tank cleanliness, pump strainers and insulation on a schedule.
- Before opening a line, isolate it, lock off if possible, drain down, and confirm zero pressure.
- Leak detection methods: visual inspection, dry surfaces, water-meter observation with all taps closed, listening with a stethoscope, dye testing in drains, and pressure testing.
- Hydrostatic testing is preferred for water pipework: fill slowly, expel air, pressurise to the specified test pressure, and hold for the specified time. A pressure drop with no visible leak indicates trapped air or a concealed leak.
- Do not use compressed air to test large plastic pipework unless the procedure and safeguards are approved; stored energy can cause violent failure.
- After repair, flush, disinfect where required, and restore supports and insulation.
Worked example
A concealed hot-water line loses pressure overnight. Close the isolating valve to the geyser and test the house line separately. If the house line holds, the fault is on the heater side; if it falls, isolate branches one by one. Suppose the bathroom branch falls only when its valve is open: the leak is on that branch. Expose the joint, repair, re-test at the specified pressure, then flush.
Traps
Do not tighten a joint under pressure. Do not assume a pressure drop always means a leak; temperature change and air can mislead. Do not test plastic pipe at a pressure above its rating. Do not leave a repaired line unflushed.