Water heater leaking? What to do right now

What to do right now

If you smell gas, skip every step below. Leave the house, do not touch light switches, and do not use a phone inside. Call the gas utility or 911 from outside or from a neighbor's phone^[4]. See gas smell near a water heater.

If there is no gas smell, do these four things in order:

1. Shut off the water to the heater. Close the shut-off valve on the cold water line, usually on the pipe above the heater's inlet^[1][2]. This stops new water from feeding the leak.
2. Shut off the heat source. Electric: switch off the water heater breaker. There may be more than one^[2]. Gas: turn the unit off using the shutdown steps on the label on the heater or in the owner's manual. A.O. Smith says to turn off power or gas before any inspection^[1].
3. Protect the area. Move stored items, put down towels, and use a bucket or wet vac. If water has reached the burner area, the controls or any wiring, stay back and call a pro.
4. Take photos. Rheem suggests photographing visible leaks, rust or unusual condensation before you call a plumber^[6]. Photos help a plumber tell the cause before the visit.

Keep the heater off while the supply valve is closed. Rheem's electric manual says not to turn the heater on unless the tank is full, and not to turn it on with the cold supply valve closed^[3].

Where is the leak coming from?

Dry everything first. Then watch where water shows up first. Water runs down the outside of the jacket, so a leak at the top often ends up as a puddle at the bottom.

Where you see water	Likely cause	Can it wait?	Who fixes it	Read more
Top: supply lines, inlet and outlet fittings, the relief valve threads, the anode port	Loose fitting or connector, worn connector, a loose anode or debris in its threads[1][5]	A slow drip can usually wait a day or two with the water off. A spray cannot	A licensed plumber. Gas units: always a pro	Leaking from the top
Bottom: drain valve	Valve not closing fully. A.O. Smith says replacement is usually the best fix[1]	Often, if it is a slow drip into a pan or bucket	A licensed plumber	Leaking from the bottom
Bottom: beads of water, sizzling under a gas burner	Condensation after a cold refill. Normal, and it fades as the tank heats[4]	Yes. Watch it for a few hours	No one, if it stops. A plumber if it keeps going	Leaking from the bottom
Bottom: from under the jacket, none of the above	Tank corrosion. Rheem says this often requires replacement[6]	No. Plan a replacement soon	A licensed plumber (replacement)	Leaking from the bottom
Relief valve or its discharge pipe	High pressure or temperature in the tank[1]	Not if it releases hot water or steam. Shut off and call	A licensed plumber. Never cap the valve	Relief valve dripping
Tankless unit: under the cabinet or from the condensate drain	Loose water connections, a blocked condensate line, or a leak inside the heat exchanger[7]	No, if water is inside the cabinet	A licensed plumber or the brand's service provider	Rinnai error codes

Electric tanks have one more spot. Rheem's service bulletin lists heating element failure as a common leak source on electric units, with rust or water trails around the element cover^[5]. Element work means draining the tank and opening an electrical compartment, so leave it to a pro.

Tankless clues. Rinnai's troubleshooting guide notes that liquid coming out of the condensate drain while the unit is not running is a common sign of a leaking heat exchanger. Some Rinnai models show code 79 when an internal leak sensor detects water^[7].

Can I still use water if my water heater is leaking?

Usually yes, for cold water. In most homes the shut-off valve on the heater's cold inlet isolates only the heater. Toilets and cold taps elsewhere in the house still work. You will not have hot water until the heater is repaired or replaced.

Two cautions. First, if you cannot reach the heater's valve, or the leak is heavy, close the main water shut-off to the house. Then nothing in the house will have water. Second, do not restart the heater with the supply closed or the tank partly empty^[3].

If the leak is only at a fitting and you need hot water for a day, ask a plumber before reopening the supply. Running a leaking unit means more water on the floor.

Is a leaking water heater dangerous?

It can be. The risks, from most to least common:

• Water damage. Slow leaks rot subfloors and drywall. Rheem notes that small amounts of condensation are normal, but pooling water indicates a problem^[6].
• Water on electrical parts. Rheem's electric manual says that if a heater has been through a flood, turn off the power and water and do not run it again until qualified service personnel check it^[3].
• Overheating. A relief valve that releases hot water or steam is a sign of excess temperature or pressure^[1]. Bradford White says that if overheating occurs or the gas supply fails to shut off, turn off the manual gas control and call a qualified service technician^[4].
• Gas. A gas smell is an emergency, separate from the leak. Follow the steps at the top of this page.

Leaks rarely fix themselves. A.O. Smith says a leak at the base is often the first sign of a serious problem^[1].

What a leak usually costs

National ranges only. Your quote depends on the cause, your area, and the heater.

Repair	Range	Source
Leak repair at valves, fittings or lines	$150 to $600	Modernize, Aug 2026[8]
Relief valve replacement	$150 to $350	Modernize, Aug 2026[8]
Anode rod replacement	$200 to $500	Modernize, Aug 2026[8]
Like-for-like 40 to 50 gallon gas tank replacement	$2,600 to $5,050	ProjectCostPro, 2026[9]
Like-for-like 40 to 50 gallon electric tank replacement	$2,550 to $4,650	ProjectCostPro, 2026[9]

Modernize lists a tank leak or tank failure as "often replacement" rather than repair^[8]. Rheem's rule of thumb: replace rather than repair if the repair costs more than 50% of a new heater, if you have needed several repairs in the past two years, or if the unit is close to or over 10 years old and having issues^[6].

For price drivers, see the replacement cost guide. To weigh age and repair history, see repair or replace.

When to call a pro

• Water is coming from the tank body or from under the jacket.
• The relief valve is releasing hot water or steam, or a steady stream.
• Water has reached the burner, gas controls, wiring or the electrical panel.
• You dried everything, watched for an hour, and still cannot find the source. An independent licensed plumber in your area can find it and quote the fix.