State Water Heater E55 Error Code — What It Means
The E55 code on State water heaters (manufactured by A. O. Smith) indicates that the unit’s leak detection system has sensed moisture or water near the heater. This is a safety feature designed to alert you to potential leaks before they cause major damage. On brand-new installations, E55 can also appear if the tank has not been completely filled with water during initial startup, causing the control to register a fault condition.
Common Causes
- Active water leak Water is leaking from the tank itself, plumbing connections, drain valve, temperature and pressure relief valve, or nearby piping and dripping onto the base or control area.
- Moisture on electrical components Water or condensation has gotten onto wiring, connectors, or the control board, triggering the leak sensor even after the source has stopped.
- Tank not fully filled (new install) During initial setup, the water heater was powered on before the tank was completely full and all air was purged from the system.
- Faulty or wet leak sensor The moisture detection sensor itself is malfunctioning or has residual water on it from installation or a previous leak.
Step-by-Step Fix
- Turn off power at the circuit breaker before inspecting the water heater to prevent shock hazards.
- Check for visible leaks around the floor, all inlet and outlet pipe connections, the drain valve at the bottom of the tank, and the T&P relief valve on the side or top of the unit.
- Inspect electrical components by removing the access panel and looking for moisture, corrosion, or water damage on wiring, connectors, and the control board. Dry any wet areas completely with a clean cloth.
- Verify the tank is full (especially on new installs) by opening a hot water tap in the house and confirming steady water flow, then checking the T&P relief valve to make sure the tank is full and air has been purged.
- Power-cycle the unit by turning the breaker off for 30 seconds, then back on. If the tank is now full and dry, the code should clear on restart.
- Recheck the leak sensor area if the code returns. Look for trapped moisture in the base pan or sensor housing and dry thoroughly before resetting again.
- Call a qualified technician if the E55 code persists after confirming the tank is full, all connections are dry, and no active leaks are present. The sensor or control assembly may need replacement.
Parts Often Needed
| Part | Notes |
|---|---|
| Leak Sensor / Moisture Sensor | Amazon | Replacement sensor if the unit false-trips after drying and leak correction. Match to your State/A. O. Smith model number. |
| Electronic Thermostat Control Assembly | Amazon | Required if the control board is damaged by moisture or the fault cannot be cleared after sensor and wiring are verified. |
| Temperature & Pressure Relief Valve | Amazon | Replace if the T&P valve is the source of the leak. Must match your heater’s pressure and temperature rating. |
| Drain Valve | Amazon | Standard brass or plastic tank drain valve if the existing valve is leaking at the base of the tank. |
When to Call a Pro
Call a licensed plumber or water heater technician if you cannot locate the source of moisture, if the E55 code returns after you have dried all components and verified the tank is full, or if you find an active leak from the tank itself (which may require tank replacement). Also call a pro if you are uncomfortable working around electrical components or if the control board shows signs of corrosion or water damage. Persistent E55 codes with no visible leak often indicate a failed sensor or control assembly that requires diagnostic tools and replacement parts.