Water Heaters
Error codes, troubleshooting, and maintenance information for water heaters.
Last updated: 2026-02-24
Error Codes
Failed upper or lower thermostat (electric), Thermostat out of calibration, Corroded thermostat wiring connections, Control board thermostat circuit failure (tankless)
Faulty thermostat not shutting off heating element, Sediment buildup insulating element causing hotspots, Stacking effect from repeated short draws, Miswired heating elements after repair
Bird nest or debris in flue pipe, Disconnected or collapsed vent pipe, Improper vent pipe installation, Excessive condensation blocking exhaust
Pilot light blown out by draft, Dirty or failed thermocouple/flame sensor, Gas supply interrupted or valve closed, Clogged burner orifice
Mineral scale buildup on flow sensor, Failed flow sensor turbine, Low water pressure below activation threshold, Inlet filter screen clogged
Corroded tank with pinhole leak, Loose inlet/outlet pipe connections, T&P relief valve dripping from excess pressure, Drain valve not fully closed or failing
Troubleshooting
View all →Common Failure Modes
Tank leaks due to internal corrosion are fatal and require complete replacement. Heating elements in electric tanks and thermocouples in gas tanks are common, easily fixable failures.
Maintenance
View all →Check for leaks and corrosion
Visually inspect around the base of the water heater, all pipe connections, and the T&P valve discharge tube for any signs of water, rust stains, or mineral deposits. Small leaks often indicate larger problems developing.
Flush the tank
Connect a garden hose to the drain valve at the bottom of the tank and drain several gallons (or the entire tank) to flush out sediment buildup. Sediment insulates the water from the heating element, reducing efficiency and eventually causing premature tank failure.
Inspect the anode rod
The anode rod is a sacrificial metal rod that attracts corrosive elements to protect the tank lining. Remove the rod from the top of the tank (may require a socket wrench) and check for heavy corrosion. Replace if less than half an inch thick or coated in calcium.
Test the temperature-pressure relief valve
Lift the lever on the T&P relief valve and let it snap back. You should hear a gurgle of water flowing into the drain tube. If no water flows or the valve leaks afterward, it needs replacement. This valve is a critical safety device that prevents tank explosion.
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