AO Smith Water Heater Leaking From Bottom — Fix Guide

What Does This Error Mean?

Water leaking from the bottom of an AO Smith tank usually means the tank itself has rusted through. This is not repairable — the unit needs replacement. A leaking drain valve is the only DIY-fixable cause.

Affected Models

AO Smith ProMax
AO Smith Signature
AO Smith Signature Premier
AO Smith Vertex

Common Causes

Rust-through of the steel tank from the inside (most common — not repairable)
Failed drain valve at the bottom of the tank (replaceable)
Pressure relief valve dripping due to high pressure
Loose cold or hot water connection on top, water running down the side
Condensation in cold weather (not a real leak)

How to Fix It

Identify the source of the leak.

Dry the area around the heater with towels. Watch where water reappears. From the drain valve = drain valve issue (fixable). From the tank seam or bottom directly = tank failure (replace unit). From above the tank = a connection.
Shut off water and power.

Turn off the cold water supply valve to the heater. For electric units, switch off the breaker. For gas units, set the gas control to OFF (not Pilot).
Tighten or replace the drain valve.

If the leak is at the drain valve, try tightening it. If still leaking, the valve seat has eroded — replace the drain valve. Drain the tank first, then unscrew the old valve and install a new one.
Check the pressure relief valve.

If the leak is at the T&P (temperature and pressure) relief valve, the system pressure is too high. Check the expansion tank if present. Replace a defective T&P valve. If the issue persists, an expansion tank may be needed.
Plan for replacement if the tank is leaking.

A leaking tank cannot be repaired safely or reliably. Shut off water and power, drain the tank, and contact a plumber for replacement. AO Smith water heaters typically last 8–12 years.

When to Call a Professional

A leaking tank is an emergency — water damage and possible electrical hazard. Shut off water and power immediately and call a plumber. Replacement is the only fix for a tank leak.