Recently a friend had this issue with a slow leak behind the wall. As a former independent insurance broker, he asked for my help with his insurance company.
It seems a major insurance carrier has no coverage for this issue, unless you purchase a separate rider, and then they limit coverage to a max of $10,000.
I hate to be an advertisement for an insurance company but The Hartford, through AARP offers an Advantage Coverage Package, that covers this issue, up to your limits of property coverage, subject to the deductible.
If there is a leak behind a wall, how can it be a maintenance issue? People don’t normally maintain pipes behind the wall.
This seems to be a problem with many homes in our community over the last few years. The first thing to do is call your insurance company, but then call a restoration company, or a public adjuster that will fight for you with your insurance carrier. If you go through an insurance agent, remember they work for the insurance company. If you go through an insurance broker, they work for you.