Polaris was engaged to evaluate a tankless water heater that failed shortly after installation, causing water damage throughout a residential structure in Texas.  Polaris’s mechanical engineering expert observed that the flow sensor of the water heater had fractured, a piece of which was embedded inside the heating element. No damage was observed at the cold or hot water lines of the tankless heater or at the stainless-steel braided hoses. However, the cold-water line inlet was observed to be dislodged from the chassis.

Review of the installation manual for the tankless water heater revealed that two wrenches were required to properly install the supply line to the cold water line inlet. Specifically, one of the wrenches was to be used to tighten the connection, while the other was needed to hold the connection so the flow sensor would not become loosened or damaged. The use of two wrenches for such a connection is also generally accepted installation practice.

Polaris’s mechanical engineering expert concluded that the plumber that installed the water heater did not secure/stabilize the flow sensor during connection of the supply line. This improper installation resulted in overtightening of the plastic housing and a minor fracture at the exit of the flow sensor. The water pressure in the supply line and flow sensor worsened the fracture overtime, ultimately resulting in the failure which led to the leak and associated water damage.