A plumbing failure due to a construction or workmanship deficit is one that will not be covered by a general homeowners insurance policy. There are workmanship exclusions included in the fine print of a homeowner’s insurance policy that exclude work done by either a contractor or a homeowner. This is why licensed plumbers carry a separate general liability insurance policy.
One of the biggest reasons plumbers charge what they do is the extreme liability that comes with working on a highly pressurized system. When you have a supply line that has a bad connection, joint, or hose it is going to create devastating problems within a matter of minutes. An open water line runs at a much higher flow rate than any fixture throughout your home. I have been called out to repair a burst pipe that was on the second floor of a home. The leak started sometime during the day when the homeowners were at work. By the time the homeowner made it back from work, there was over $40,000 worth of damage to their home. As a licensed plumber in Knoxville, I see this happen on a regular basis.