No. First of all, casualty losses are only deductible if the loss was caused due to a federally declared disaster (like a flood or wildfire).
Second, damage caused by a slow leak over time is never considered a casualty loss, even if it was otherwise deductible. A casualty loss is a sudden, unexpected and unpreventable event. A slow leak is not detectable and it is preventable, at least in theory, by early detection.
