Gas units depend on a sealed gas line, proper venting, the gas valve, the burner assembly, and the pilot tube. Electric units run two heating elements, two thermostats, and a high limit switch, and most calls are one of the two elements or thermostats. Tankless units add the heat exchanger, which scales up under hard water; an annual descaling flush is the maintenance that keeps that from being a problem. Rinnai, Navien, and Bosch tankless units throw specific fault codes we read on site with the manufacturer apps. Hybrid heat pump units, including the Rheem ProTerra and AO Smith Voltex, add a heat pump fan, an evaporator coil, and a condensate drain line to the standard tank.
When repair makes sense, we repair. Many calls are resolved with a new heating element, thermocouple, gas valve, or igniter, and we always present a repair option when one is reasonable. Our recent water heater repair versus replace guide walks through the framework we use to decide when a small repair is the right answer and when replacement is the better long term value.