Flashing lights on tank-style units
Many gas tank water heaters use a simple flashing LED pattern — a certain number of flashes repeated in a pattern — to indicate status codes ranging from "normal operation" to specific fault conditions like a flame sensor issue or a blocked vent. The flash pattern (count and spacing) is what actually identifies the code, so it's worth timing it or recording a short video before calling.
Numeric error codes on tankless and digital units
Tankless units and newer digital tank models typically display an actual number or letter-number combination rather than a flash pattern. These usually map to categories like ignition failure, overheat protection, a sensor fault, or a flow or combustion issue — each with a different likely cause and fix.
What usually causes the most common codes
A large share of error codes across brands trace back to one of a handful of root causes: a blocked or restricted vent, a dirty flame sensor or igniter, mineral scale buildup inside a tankless heat exchanger, or a gas supply or pressure issue. Which one applies depends on the specific code and the unit's age and maintenance history.
When to reset it yourself vs. call a plumber
A single, one-time code after a power blip is sometimes safe to reset by following the manufacturer's reset procedure. A code that returns repeatedly, especially anything related to gas, flame, or overheat protection, shouldn't be reset and ignored — it's the unit telling you something needs an actual repair.
Rheem is one of the most common water heater brands we service in Marietta, and its Guardian System flash codes are a good example of how these patterns work — but the same logic applies across most major brands. If your unit is flashing or displaying a code, we can identify it and the actual fix during one visit.