A.O. Smith Water Heater Leaking — What’s Happening
A leak from your A.O. Smith water heater means water is escaping from some part of the unit or its connected piping. This is a physical symptom, not an electronic fault code. The manufacturer’s guidance is to identify the exact source of the leak before deciding on a repair. Common sources include pipe fittings, the temperature-and-pressure relief valve, the drain valve, and in the worst cases the tank itself.
A.O. Smith’s published maintenance information makes clear that most leaks are caused by poor or loose connections rather than a cracked tank. That means many leaks can be stopped with simple tightening or valve replacement. If the tank body itself is corroded or cracked, replacement of the entire water heater is typically required.
Most Likely Causes
- Loose or poor water connections The manufacturer states that most leaks are caused by poor connections rather than tank failure, and pipe fittings may only need tightening if the leak is external to the tank body.
- Faulty or leaking drain valve The drain valve can leak if it is loose, cracked, or does not close properly.
- Temperature-and-pressure relief valve discharge The T&P valve can leak if the valve itself is faulty or if system pressure or temperature is too high.
- Excessive water pressure in the plumbing system High water pressure can force leakage, especially at the T&P valve, and A.O. Smith recommends a pressure-reducing valve if water pressure exceeds code maximum of 80 psi.
- Corroded or cracked tank If the tank itself is cracked or corroded, replacement of the water heater is typically required rather than repair.
How to Diagnose and Fix
- Shut off power (electric models) or gas (gas models) to the water heater before inspection.
- Shut off the cold-water supply valve to stop further leakage.
- Locate the exact source of the water by inspecting the top fittings, side connections, T&P discharge pipe, drain valve, and tank shell.
- If the leak is at a pipe fitting, gently tighten it without overtightening.
- If the leak is at the drain valve, plan to replace the valve.
- If the T&P valve is discharging, check system water pressure with a gauge and verify it does not exceed 80 psi.
- Inspect the tank body for corrosion or cracks, and plan for heater replacement if the tank is compromised.
- After repairs, restore power or gas and the water supply, then recheck all connections for leaks.
Parts You Might Need
| Part | Notes |
|---|---|
| Temperature-and-pressure relief valve | Amazon | Replace if leaking or faulty. |
| Drain valve | Amazon | Replace if leaking or not closing properly. |
| Pressure-reducing valve (PRV) | Amazon | Install on main water line if pressure exceeds 80 psi. |
| Expansion tank | Amazon | May be needed if T&P valve discharges from thermal expansion. |
Related Error Codes
If your appliance also shows a code on the display, these match this problem:
- A O Smith Water Heater E2 error code
- A O Smith Water Heater E4 error code
- A O Smith Water Heater E6 error code
When to Call a Pro
Call a licensed plumber if the leak is coming from the tank body itself, if you cannot locate the source of the leak, or if system pressure remains high after installing a PRV. Tank replacement requires proper disconnection of gas lines (on gas models), electrical wiring, water piping, and safe disposal of the old unit. If the T&P valve continues to discharge after you have checked pressure and temperature settings, a pro should verify that the valve is sized correctly and that an expansion tank is properly installed and charged. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.