Florida Subscriber

You present a very logical argument for coverage. The septic tank, by virtue of being part of the dwelling's plumbing system, is covered as a part of the dwelling even though it is located outside the dwelling's walls. Remember that structures attached to a dwelling are covered under coverage A. The additional coverage for glass breakage does not state that the glass must be part of a door or window. The glass must be part of a covered building, but the septic system meets that criterion. Webster's Collegiate Dictionary (Tenth Edition) says that fiberglass is simply glass in fibrous form, so it cannot be argued that fiberglass is not truly glass.

Further, the insuring agreement for the coverage states that the insurer covers breakage, with no limitations or exclusions except for vacancy of the dwelling, which is not the case here. 

It might also be possible to consider coverage under the additional coverage of reasonable repairs. Replacing the tank could protect against further damage as well as the threat of a suit when it is learned the waste is entering the ground water.