Cold and Hot Water Supply Installation and Testing
Domain focus
This domain tests cold and hot water supply installation, storage, distribution, testing and commissioning. It includes tanks, pumps, cylinders, valves, insulation, backflow control and pressure testing.
Core rules
- Cold water: maintain an air gap at the storage tank, screen the inlet, support the tank, and prevent backflow by correct arrangement.
- Hot water: fit a cylinder with expansion control, temperature limiting and insulation; avoid long dead legs.
- Use isolation valves at fixtures and groups; label pipes and direction of flow.
- Test before concealment: fill slowly, vent air, isolate, and apply the specified hydrostatic test-typically 1.5 times design pressure or the project minimum.
- Hold the test, inspect every joint, and record gauge readings. Flush and chlorinate where specified.
- Do not test a hot-water cylinder beyond its rated pressure.
Worked example
Design pressure is 300 kPa. The nominal test is 1.5 × 300 = 450 kPa, but the specification sets a 1000 kPa minimum for this project. Use 1000 kPa, provided the components are rated for it. The reasoning is that the higher of the calculated and specified minimum governs.
Traps
Testing with air instead of water; leaving the gauge on a live line; failing to vent air; testing the cylinder at mains pressure; no isolation at fixtures; ignoring thermal expansion.