A leaking water heater ranges from a minor, fixable drip to a failing tank that needs replacing. The good news is that where the water is coming from tells you which. A leak from the top is often a loose fitting or a valve you can address; a leak from the bottom of the tank usually means internal corrosion, which cannot be repaired. This guide helps you find the source, act safely, and decide whether to repair or replace.
First Steps: Make It Safe
- Turn off the power or gas: for an electric unit, switch off its breaker; for a gas unit, turn the gas control to the OFF or pilot position.
- Turn off the cold water supply: close the shut-off valve on the cold inlet at the top of the tank so no more water feeds the leak.
- Contain the water: mop up standing water and keep it away from electrical outlets and the furnace.
- Then diagnose where the leak is coming from.
Leaking from the Top
A leak at the top of the tank is often repairable. The usual sources are loose cold-inlet or hot-outlet fittings, a leaking temperature and pressure (T&P) relief valve, or condensation on a gas unit. Tightening a fitting or replacing a valve can solve it. Top leaks are worth a technician visit because they are frequently a repair rather than a full replacement.
Water Heater Leaking from the Bottom
A leak from the bottom of the tank is the more serious one. It usually means the steel tank has corroded internally and water is escaping through the shell, which cannot be repaired; the unit needs replacing. But water pooling at the base does not always come from the base. Before assuming the worst, work through these sources in order, with the power or gas and the cold water supply already shut off.
The drain valve
The spigot near the bottom of the tank is used for flushing. Wipe it dry and watch it. If water beads at the valve outlet or around its threads, the valve is the leak. A loose or worn drain valve is a repair, not a reason to replace the tank.
The T&P discharge pipe
The temperature and pressure relief valve on the side or top of the tank has a pipe that runs down toward the floor. If the end of that pipe is wet, the water at the base came from the valve, not the tank. That points to a failed valve or a tank that is getting too hot or over-pressurized, which a technician should diagnose.
A leak higher up
Water from a loose inlet or outlet fitting at the top of the tank can run down the outside and collect at the base. Dry the tank and check the top connections and the pipes above it.
Condensation (gas units)
A gas water heater can drip condensation onto the burner area, especially when it refills with cold water. Condensation is light, comes and goes, and stops once the tank is up to temperature. A steady flow is not condensation.
The tank itself
If the drain valve, discharge pipe, and fittings are all dry and water keeps appearing under the tank, the tank shell has failed. It cannot be patched. Plan for a replacement soon, because a corroded tank can give way and flood the area.
Pressure Relief (T&P) Valve Leaking
The temperature and pressure relief valve is a safety device that releases water if the tank gets too hot or over-pressurized. A little discharge can be normal, but a steady drip means either the valve is doing its job because pressure or temperature is too high (a real problem to diagnose) or the valve itself has failed and needs replacing. Do not cap or plug this valve; it is a critical safety component.
Is a Leaking Water Heater Dangerous?
A slow leak is mostly a water-damage and mould risk, but it can become dangerous: water near the electrical connections of an electric unit or near a gas burner is a hazard, and a tank leaking because of over-pressure is a safety issue. If you smell gas, do not touch anything: leave and call Enbridge at 1-866-763-5427 from outside. Otherwise, shut off the power or gas and the water supply. A tank can also fail suddenly and flood, so a bottom leak should not be ignored.
Repair or Replace?
- Repairable: loose fittings, a failed drain valve, or a failed T&P valve on an otherwise sound tank.
- Replace: a tank leaking from the bottom shell (internal corrosion), or any tank near or past its 8 to 12 year lifespan.
- Rule of thumb: if the tank body is leaking or the unit is over 10 years old, replacement is the sensible call. A new tank runs about $1,400 to $2,200 installed.
When to Call a Technician
Call EcoFrost once you have shut off the water and power or gas. We identify whether it is a repairable valve or fitting or a failed tank, and we replace gas, electric, and tankless water heaters across the GTA, often same day. If the tank is leaking from the bottom, do not wait, as it can fail and flood.
One check before you book anyone: a rental provider sticker on the tank, or a rental line on your gas or hydro bill, means the provider is responsible for the repair. Our Toronto water heater repair page explains how we confirm ownership on arrival.
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