Installation, Commissioning and Field Testing
What the exam tests here
Whether you can install to specification, pressure-test properly, commission zone by zone, and prove performance with measured numbers rather than impressions.
Core rules
- Survey and mark alignment first; place the head unit on high, firm, flood-safe ground close to the source.
- Trench mains and submains 30–45 cm deep and laterals 15–20 cm. PVC jointing: cut square, clean, apply solvent cement to both surfaces, push with a quarter turn, hold 30 seconds, cure 24 hours before pressure testing.
- Flush mains and laterals before fitting emitters or end caps; punch holes with a proper punch tool, not a nail.
- Hydro-test at 1.5 times working pressure, or at least 5 kg/cm², for one hour, and watch the joints rather than the pump.
- Commissioning: run each section, record pressure at head and tail, measure emitter discharge, compute EU, train the farmer and hand over documents.
Worked example
Eight emitters sampled along a lateral give 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1 and 4.2 lph. Mean = 3.85 lph; mean of the lowest quarter = (3.5 + 3.6) ÷ 2 = 3.55. EU = 3.55 ÷ 3.85 × 100 = 92.2%, which is acceptable. If the figure were 78%, the likely causes would be excessive lateral length, low inlet pressure or a blocked filter - investigate before handover.
Traps that cost marks
- Pressure-testing before the solvent cement has cured.
- Measuring flow at the head instead of at field emitters.
- Skipping the flush and later blaming the emitters for clogging.
- Handing over without a signed installation report and a farmer demonstration.
Quick recall
Trench, joint, cure, flush, test, measure, hand over.