Yes, if the insured is liable for the resulting water damage, the general liability policy will apply. This is a completed operations claim, and the only exclusion that would apply is exclusion l., damage to your work. This exclusion applies to property damage to the named insured's work arising out of that work. So, if the insured caused damage to his own work, for example, the water line, that would not be covered; but, if his work caused damage to another's property, for example, the damage caused by the leaking water, that is covered by the general liability policy.

The liability policy does apply to the claim if the insured is liable for the damage. Whether he is liable is, of course, a legal question that we cannot answer and you should contact an attorney in your area who is familiar with the law there on this point. But, if the insured is liable, the general liability policy will apply.

There is one more comment. For informational purposes, generally, the policy in effect at the time the damage is discovered or manifests itself is the policy that will apply to the property damage claim.