Testing, Maintenance, Repair and Troubleshooting
This domain covers pressure and leak testing, planned maintenance, fault diagnosis and repair quality. Questions ask you to choose the right test, interpret gauge readings, and find the root cause instead of replacing parts at random.
Testing
Water-supply pipework is commonly hydrostatically tested at about 1.5 times the working pressure, or the specified minimum, held long enough to reveal leaks - often at least one hour. Isolate the section, fill slowly, vent air, and watch the gauge for a steady drop. Drainage is tested by water, air or smoke test, with trap seals protected. Never use compressed air to test plastic pressure pipe unless the procedure and safeguards specifically allow it.
Maintenance and diagnosis
Keep a schedule for strainers, valves, taps, geysers, tanks, pumps and relief valves. For low pressure, measure at two points: if pressure is low at the tank outlet and at the tap, the problem is supply, tank level or pump; if it falls only at the tap, look for a blocked strainer, partly closed valve, scale or undersized branch. For a blocked drain, locate the blockage with a rod or camera before jetting. For a leaking joint, identify whether it is thread, solvent, solder or seal failure.
Worked example
A first-floor tap has poor flow but the ground-floor tap is normal. Fit a gauge at the tank outlet: 1.1 bar. Fit a gauge at the first-floor tap: 0.3 bar. The 0.8 bar loss over that branch points to friction or a restriction - check the strainer, isolation valve, scale and pipe size before replacing the tap.
Traps that cost marks
Do not over-pressurize a system to find a leak; do not test without isolating and venting; do not repair a symptom without finding the cause; and do not leave a system under test unattended without recording the gauge reading.