Ongoing neighbor-caused water intrusion — was advised to report but not file claim. Next steps?

For ~2 years we’ve had slow water migration from a neighboring property. Recently, after pulling flooring, we discovered moisture beneath our slab foundation.

Evidence so far:

• Trenching along the affected side shows water collecting within 24–48 hours (no rain, no water use on our side) • Our water meter shows no abnormal usage • Neighbor’s meter increased ~90 units in under 24 hours with no intentional use

• Leak detection ruled out plumbing/irrigation on our property

The neighbor had limited pool testing back in May (bucket + dye only). More thorough pool tests were not done. A plumber is coming Monday, but the plumbing company confirmed they do not perform pool leak detection.

I notified my homeowners insurance but did not open a claim since this is an ongoing condition, not a sudden loss. My adjuster suggested asking the neighbor to open a liability claim so their insurer could investigate. I relayed that, but haven’t received a response.

Additional context: The neighboring property is held in a trust. The executor does not reside at the property; a family member occupies the home. The water account may be on autopay, which could explain why elevated usage went unnoticed. This is included for context only.

My questions: • Is documenting without filing a claim still the right approach? • At what point should I formally open a claim to protect myself? • Do insurers rely on hydrologist / forensic reports for subsurface water migration?

Thanks for any insight.