No hot water? What to check before you call

Safety first

Gas water heaters burn fuel inside your home. Rheem’s manual says that if you smell gas, do not light anything, touch electrical switches or use a phone in the home – call the gas supplier from a neighbor’s phone, or the fire department if you cannot reach it, and stay out until they say it is safe. Keep gasoline and other flammable liquids away from a gas water heater, and do not use one that has been under water until a qualified technician has inspected it. A carbon monoxide alarm sounding is a reason to leave and call 911.

Gas or electric?

A gas heater has a burner at the bottom and a vent pipe on top. An electric heater has no vent and usually two panels on the side covering the heating elements and thermostats. A storage tank keeps a reservoir of hot water and draws from the top of the tank when a hot tap opens, as the U.S. Department of Energy describes it – so running out can also simply mean the tank has been emptied faster than it can reheat.

Electric water heater: power and the reset

Check the breaker for the water heater. Electric heaters also have a high-temperature limit control that cuts power if the water gets too hot – Rheem notes this can cause a no-hot-water situation. On the Rheem model we checked, resetting it means turning off the power, removing the control cover and insulation, and pressing the red reset button. Follow the manual for your own model, and never work behind the covers with the power on. If the limit trips again, a thermostat or element is likely failing – call a plumber or the manufacturer.

Gas water heater: gas and the burner

Make sure the gas valve to the heater is open and that other gas appliances work. Many gas heaters have a small window to see the burner or pilot. Relighting instructions are printed on the label on the heater itself – follow them exactly. If the pilot will not stay lit, or the control shows an error code, call a plumber and tell them the code.

Temperature setting

Someone may have turned the dial down. The U.S. Consumer Product Safety Commission urges households to set water heaters to 120 degrees F, and notes that lowering the temperature also saves energy. You can check what comes out of the tap with a candy or meat thermometer under the faucet, CPSC says. Do not turn it up much higher to “get more hot water”: CPSC says burns can occur in six seconds at 140 degrees F, and most tap-water scald injuries involve older adults and children under five.

Lukewarm water or running out fast

• Sediment. Minerals settle at the bottom of a tank and reduce how much hot water it holds. Rheem suggests draining a few quarts from the tank monthly to clear sediment; check your own manual.
• One failed element on an electric heater often means water that is only warm.
• Demand. Back-to-back showers, laundry and the dishwasher can outrun a small tank.
• Only one tap affected? The problem may be a mixing valve in that faucet, not the heater.

Repair or replace?

The Department of Energy puts the life of a storage water heater at about 10 to 15 years. An older heater with a failing part may be worth replacing rather than repairing, especially if it is also leaking. Water heating is about 18 percent of a home’s energy use, according to DOE, so a replacement is a chance to look at more efficient options – see tank vs tankless.

When to call a plumber

• Any gas smell, or a pilot that will not stay lit.
• An electric heater that keeps tripping its breaker or limit control.
• Water leaking from the tank, or rusty or smelly hot water.
• Rumbling or popping that is getting worse.
• Any work on gas lines, venting or wiring.