Water Heater Leaking? Call Emergency Plumber — Now

Walking into a garage or utility room and finding water around the base of the water heater is one of those moments where your first instinct is to assume the worst. Sometimes that instinct is right. But often the leak is coming from a connection or valve — not the tank itself — and the fix is straightforward.

The location of the water heater leaking tells you almost everything you need to know before calling anyone.

Step One: Turn It Off, Then Diagnose

Before you do anything else:

• Gas heater: Turn the thermostat dial to the "Pilot" position
• Electric heater: Flip the circuit breaker for the water heater to OFF
• Cold water supply: Find the cold water inlet valve at the top of the unit and turn it off (clockwise)

Now the heater isn't adding heat or receiving more water. You can inspect it safely.

Locate the Leak: Working from Top to Bottom

Leaking from the Top: Cold/Hot Water Connections

At the top of every tank water heater are two pipe connections — cold water inlet and hot water outlet. These connect to the household plumbing above. The connections are threaded, often with flexible stainless steel supply lines running to them.

Dripping or moisture at the top almost always means a loose fitting or a failed supply line connection. These are the easiest water heater leaks to fix.

Fix: Tighten the connection with a wrench — sometimes that's all it takes. If there's still a drip, the supply line itself has a hairline crack or the fitting thread sealant has failed. Replace the supply line ($10–$15 for a braided stainless replacement) or reseal the threaded fitting with Teflon tape and pipe dope.

Leaking from the T&P Relief Valve

The temperature and pressure relief valve (T&P valve) is a safety device on the side of the tank, usually with a small pipe running down the side toward the floor. Its job is to open and release water if tank pressure or temperature exceeds safe limits.

If water is dripping from the T&P valve discharge pipe, it means one of two things:

• The valve is doing its job — temperature or pressure inside the tank exceeded the safety threshold and the valve opened. This is a sign your thermostat is set too high or your pressure relief is being triggered by high system pressure. Both need to be addressed.
• The valve itself has failed — the internal spring has weakened and the valve now weeps water under normal operating conditions. A failed T&P valve needs to be replaced, not ignored.

T&P valve replacement costs $20–$40 in parts and is a 30-minute job for a plumber. If the valve was discharging due to high temperature or pressure, those root causes need to be addressed too. Do not plug or cap a T&P valve discharge — it's there to prevent tank explosions.

Leaking from the Drain Valve

Near the bottom of the tank is a drain valve — it looks like a hose bib and is used for tank flushing and maintenance. These plastic or brass valves develop leaks from corrosion, debris in the valve seat, or a worn washer.

Try attaching a hose and opening the valve briefly to flush any debris, then close it firmly. If the drip continues, replace the drain valve. It's accessible without removing the tank — shut off the cold water, partially drain the tank via a bucket, unscrew the old valve, apply Teflon tape to the new valve threads, and install. Parts cost $10–$25. A plumber charges $50–$150 for this.

Leaking from the Tank Body

This is the bad news scenario. If water is seeping from the tank body itself — not from a valve or fitting, but from the metal walls or base of the tank — the tank has corroded through internally. This is the heater tank leak that cannot be repaired.

Sediment accumulates at the bottom of tank heaters over years. When the anode rod (the sacrificial metal rod that protects the tank walls from corrosion) has been consumed, the tank walls begin to rust from the inside. Eventually the corrosion creates a pinhole or seam crack that leaks water. Once this starts, it accelerates — and the tank can fail suddenly and completely.

The correct response to a leaking tank body is replacement. There is no patch, no seal, no repair that fixes internal tank corrosion reliably. If the heater is under warranty, contact the manufacturer — most tank heaters have 6–12 year warranties, and tank failure is typically covered.

Is It Actually a Leak or Condensation?

Before assuming the worst, check whether the moisture around the heater might be condensation rather than a leak. Condensation forms on the outside of a cold tank when it's surrounded by warm, humid air — particularly common when the heater is in a garage in humid climates. Condensation moisture is a light, even film on the tank exterior and disappears once the tank heats up.

A genuine leak produces a dripping or seeping pattern that originates from a specific point and doesn't disappear when the tank runs. Dry the exterior with a cloth, run the heater for an hour, and check again — condensation won't return on a hot tank, but a real leak will.

Repair vs. Replace Decision

Use this framework:

Leak Source	Repair or Replace?
Supply line connection (top)	Repair — $10–$50 DIY
T&P valve dripping	Repair — replace valve ($100–$200 with plumber)
Drain valve dripping	Repair — replace valve ($50–$150 with plumber)
Tank body / base seeping	Replace — no repair possible
Tank over 10 years old + any leak	Replace — cost of repair rarely worthwhile

How Long Should a Water Heater Last?

Tank water heaters have an average lifespan of 8–12 years. A few factors that affect this significantly:

• Water quality: Hard water accelerates internal corrosion and sediment buildup. Homes in hard water areas (much of the Southwest, Midwest, and Southeast) often see heaters fail at 8–10 years.
• Anode rod maintenance: The sacrificial anode rod should be inspected every 3 years and replaced when it's reduced to a thin wire core. Most homeowners never do this — which is why most tanks fail prematurely.
• Annual flushing: Flushing 2–4 gallons from the drain valve annually removes sediment that otherwise builds up at the tank bottom, accelerating corrosion and reducing heating efficiency.
• First-hour rating matching usage: A heater that's consistently undersized for household demand runs more, heats more cycles, and wears out faster.

When Should You Just Replace It?

Even if the leak is repairable, consider replacement if:

• The unit is 10+ years old
• The tank has visible rust at the base or discharge pipe
• Hot water has been discolored or smelled rusty recently (internal corrosion)
• The repair cost exceeds 30–40% of a new unit's cost
• You're already unhappy with its recovery time or hot water volume

A new 40-gallon tank heater installed typically runs $800–$1,500. A tankless (on-demand) water heater is $1,500–$3,500 installed but has a 20+ year lifespan and can reduce water heating costs by 20–35%. If you're replacing a failed tank, it's worth getting a quote on tankless at the same time.

Also check: if you're also dealing with no hot water in the house, a leaking tank may explain why — a significantly depleted tank from a slow leak can't maintain hot water volume. And if water damage from the leak has reached adjacent areas, see our guide on water leaking from ceiling if the heater is on an upper floor.

Safety Tips for Water Heater Leaks

• Never cap or plug the T&P valve — it's a pressure safety device, not a simple leak
• Don't use power tools near a gas heater with an active leak — gas connections near the unit may be compromised
• For electric heaters, always turn off the circuit breaker before working near any water-affected components
• If the heater is in a basement and water is near electrical outlets or the panel, prioritize getting power off before wading in

Frequently Asked Questions