High liability note: This topic requires careful language. A pool leak detector is not a structural engineer, geotechnical engineer, or forensic investigator. Surface indications are observable and documentable. Sub-deck void confirmation is not within leak detection scope.
Never write "confirmed sub-deck void" in a report unless that conclusion was made by a qualified professional whose findings you are referencing. Document observations only. Recommend evaluation. Refer the structural conclusion to the right professional.
What Surface Indications Can Be Observed
Sinking or rocking pavers
Deck pavers that have settled, shifted, or rock underfoot suggest the substrate beneath them has moved or been eroded. This is observable and photographable. The cause - pool leak, irrigation, drainage, poor compaction, or ground movement - is a separate question that the surface observation alone does not answer.
Settled or cracked concrete sections
A concrete deck that has cracked along a linear pattern, settled unevenly, or created a step-down at a joint may indicate that the underlying soil has shifted. Photograph the crack pattern, measure the settlement if visible, and note the location relative to the pool and the suspected plumbing area.
Gaps at coping or pool edge
Gaps appearing between the coping and the deck, or between the coping and the pool shell, can indicate differential movement between the pool structure and the surrounding deck. This may result from soil erosion beneath the deck or from the pool and deck moving independently.
Hollow-sounding deck areas
Tapping the deck surface with a mallet or foot in an area near a suspected underground leak and hearing a hollow sound suggests that material beneath the surface deck has moved or been washed away. This is an observational finding - not a void confirmation.
Recurring damp surface areas
A deck surface that remains damp or shows persistent wet areas in dry weather may indicate water is moving through or collecting under the deck. Photograph the area, note the conditions, and document the proximity to the suspected plumbing location.
- "Surface indications observed in the area of [location]: settled pavers, hollow sound when tapped, gap at coping."
- "These observations may be consistent with sub-deck movement or soil erosion. Further evaluation by a qualified contractor, structural engineer, or geotechnical professional is recommended before any deck or excavation work is planned."
- "Cause of surface settlement was not determined during this evaluation. Multiple causes are possible including pool plumbing leak, irrigation, drainage, compaction, or ground movement."
- Do NOT write: "Confirmed sub-deck void." Do NOT write: "Void caused by pool plumbing leak." These are forensic conclusions that require professional engineering evaluation.
Document only what you can see and test. A hollow-sounding area near a pressure-tested failing return line is a significant combined finding - document both clearly. But the report says "surface indicates possible sub-deck concern in this area" not "void confirmed." The structural professional confirms the void. The leak detector confirms the leak and documents the surface observations.
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