Maintenance, Repair and Testing
Maintenance, Repair and Testing tests fault-finding, safe repair and proving a system before handover. The exam favours method: isolate, drain, repair, test, disinfect and record.
Maintenance
Preventive checks include valve exercising, strainer cleaning, flushing, lagging and leak surveys. Leaks on GI often occur at threaded joints; on PVC at solvent joints; on copper at soldered elbows. Use the correct replacement part, not a larger clamp.
Testing
- Water supply: hydrostatic test at 1.5× working pressure or a specified minimum head, held without pressure drop.
- Drainage: water test or smoke test to prove joints and trap seals.
- Disinfection: chlorinate the tank, hold, drain and flush. Always cure solvent joints before testing.
Worked example
A supply main works at 4 bar. The test pressure is 1.5 × 4 = 6 bar. Pressurise slowly, vent air, hold for the specified period, often 1 hour, and check for pressure drop and visible leaks. A drop means a joint or valve is leaking; do not simply top up and pass it.
Traps
Testing a PVC line immediately after solvent welding; using a smoke test on a water main; over-pressurising a plastic line; and repairing a leak without checking the cause.