CSLB C-27 Landscaping ContractorIrrigation SystemsHard
A landscape contractor is performing a system audit on an existing irrigation system. They observe that one zone has significant dry spots between sprinkler heads, despite appearing to have adequate pressure and flow. The sprinkler heads in this zone are spaced 30 feet apart, and each head has a radius of throw of 15 feet. What is the most probable cause of the dry spots?
- AThe nozzles on the sprinkler heads are partially clogged.
- BThe sprinkler heads are spaced too far apart for head-to-head coverage.
- CInsufficient operating pressure for the sprinkler heads.
- DThe controller is programmed for an incorrect run time for the zone.
Show answer & explanationAnswer & explanation
Correct answer: B. The sprinkler heads are spaced too far apart for head-to-head coverage.
Effective irrigation requires 'head-to-head' or 'overlap' coverage, meaning each sprinkler should spray to the adjacent sprinkler head. If heads are spaced 30 feet apart but only have a 15-foot radius, there will be a 15-foot gap in coverage between them, leading to dry spots. This is a fundamental design flaw.
Why the other options are wrong
- A. Partially clogged nozzles would result in reduced throw, but the primary issue described is a systemic spacing problem, not just individual head underperformance.
- C. The question states 'adequate pressure and flow', so this is unlikely to be the primary cause.
- D. Incorrect run time would lead to general underwatering or overwatering, not specific dry spots between heads when pressure/flow are adequate.
Head-to-Head Spacing
Sprinkler heads must be spaced so that the throw of one head reaches the adjacent heads, ensuring uniform water distribution and preventing dry spots.
- Spacing should be equal to or less than the radius of throw.
- Ensures all areas receive water from multiple heads.
- Prevents dry spots and promotes even growth.
Memory trick: Head to head, no dry spots spread.