Short answer: if every fitting and valve on top is dry and water keeps collecting under the heater, the steel tank has corroded through and has to be replaced. Tank leaks cannot be welded or patched. First rule out connector leaks, relief valve drips and condensation, then, if the tank is the source, arrange water heater leak repair in Diamond Bar that includes a replacement quote.
How tanks corrode from the inside
A storage water heater is a steel tank with a thin glass lining. Over time, tiny cracks let water reach the steel. To slow that, tanks contain a sacrificial anode rod, usually magnesium or aluminum, that corrodes first so the tank does not. When the rod is used up, the steel starts to rust, and the rust eventually becomes a pinhole leak or a seam failure.
Hard water speeds this up in two ways: scale and sediment settle at the bottom, which overheats the lining and hides corrosion, and the anode rod is consumed faster. In places with hard supply, such as the parts of Walnut and Rowland Heights served by Walnut Valley Water District, or Pomona’s groundwater-based system, maintenance matters more.
Is it really the tank? Rule out these first
| What you see | What it might be | How to tell |
|---|---|---|
| Damp base, dry fittings, hot-water use just ended | Condensation, especially on a gas heater or in a cool garage | Moisture is light and stops once the heater is idle for a few hours |
| Drips along a pipe on the side | Relief valve discharge | Follow the pipe. See relief valve leaks |
| Wet top of the tank | Connector or valve leak running down the jacket | Dry the heater and watch which joint beads first. See flex line and valve leaks |
| Drip at the drain valve | Worn drain valve | Water from the small spigot near the bottom. Often replaceable |
| Steady water under the tank, rust streaks on the jacket | Tank corrosion | No other source. Usually accompanied by rusty hot water or rumbling |
Signs a tank is near the end
- Rust-colored or metallic-smelling hot water, while cold water runs clear
- Rumbling, popping or knocking from sediment cooking at the bottom
- Rust streaks or flaking on the base, or a corroded drain valve
- A heater well into the 8 to 12 year range that manufacturers commonly cite
- Reduced hot water capacity as sediment fills the tank
Can an anode rod or a flush save the tank?
Maintenance prevents failures, but it cannot reverse one. Checking or replacing the anode rod every few years, as many manufacturers suggest, and flushing sediment can extend a healthy tank’s life. Once water is escaping through the shell, the liner has already been breached, and no rod or flush will stop the leak. A plumber can confirm by inspecting the tank base and the burner or element compartment.
What to do right now
- Close the cold-water supply to the heater. That stops the flow and limits the damage. See our first-ten-minutes checklist.
- Turn off power or gas if the control is safe to reach. If you smell gas, leave and call 911 or SoCalGas at 1-800-427-2200.
- Contain and photograph the water. Photos help with insurance and landlord reports.
- Call and ask for an on-site inspection and a written replacement quote. Ask about permit, bracing, haul-away and warranty.
Need a plumber for this? Describe the leak and your address. If a provider covers your area, you can ask about fees, timing and scope before agreeing to anything.
Call +1 (909) 760-1466When a tank leak has already soaked flooring or drywall, read our guide to drying and extraction. The sooner materials are dried, the less likely mold and rot become an added cost. To reach a plumber, see how the referral service works.
Frequently asked questions
Can a leaking water heater tank be repaired?
No. If the leak comes through the tank shell or lining, the tank has corroded and cannot be reliably patched. The heater has to be replaced. Leaks at connectors, valves and the drain valve are different and are usually repairable.
What does an anode rod do?
It is a sacrificial metal rod inside the tank. Because it is more reactive than steel, it corrodes first and protects the tank from rust. Once it is used up, the tank itself begins to corrode.
How often should an anode rod be replaced?
There is no single schedule. Many manufacturers recommend checking it every few years, and more often with hard water or a softener. A plumber can inspect it and tell you how much is left.
Is a small puddle under the heater an emergency?
It is urgent, because a tank that is weeping can fail suddenly and release the rest of its contents. Close the supply, turn off the heat source if safe, and arrange an inspection promptly.
Will a water softener help my heater last longer?
Softened water reduces scale, though it can also use up some anode rods faster, so ask your plumber about the right rod. Local hardness varies, so check your water provider’s annual report.
Sources and further reading
Related guides
- Emergency water heater leak repairWhat to do in the first ten minutes, how to find where the water is really coming from, and when to call right away.
- Replacing a leaking water heaterWhen a leak means replacement, what a California-compliant installation includes, and how permits and bracing fit in.
- Tankless leaks, scale and flushingWhere tankless units leak, how hard-water scale builds up, and what a descaling flush involves.