No hot water: what to check on gas, electric and tankless heaters

Start with what you're seeing

If No hot water anywhere in the house

The heater isn't heating. Go to the checks for your heater type below.

If Hot water at some faucets but not one

That fixture's mixing valve or cartridge, not the heater. See faucet repair.

If Hot at first, then lukewarm within minutes

Lost capacity: sediment, a broken dip tube, or one failed element on an electric heater.

If Water is too hot or the relief valve is discharging

Turn the heater off and call. A stuck thermostat or gas valve is a safety issue.

If Tankless unit shows a code

Note the code before resetting; it tells the plumber where to start.

Gas tank heaters

1. 1

   Check the status light or window

   Many modern gas controls blink a pattern when the pilot or flame sensor has failed. The pattern is decoded on the label.

2. 2

   Relight only if the label says how

   Follow the printed lighting instructions exactly. If you smell gas, don't relight; leave and call the gas utility.

3. 3

   Pilot won't stay lit

   A pilot that lights but goes out when you release the knob usually means a worn thermocouple or flame sensor.

Caution: Gas controls, burners and venting are not DIY parts. Anything beyond the printed relighting steps belongs to a licensed plumber.

Electric tank heaters

1. 1

   Check the breaker

   A double-pole breaker for the heater may have tripped. Reset it once. If it trips again, stop and call.

2. 2

   The reset button

   Behind the upper access panel there's a red high-limit reset. Pressing it once is reasonable; if it trips again, there's a fault, often a shorted element or thermostat.

Caution: Turn off power before removing access panels. Elements and thermostats carry 240 volts.

Why hot water runs out too fast

• Sediment buildup

  Most common

  Tell: Popping or rumbling sounds, gradually shorter showers, common in hard-water areas.

  Fix: Flushing can help if the tank isn't too far gone. See water heater maintenance.

  Water Heater Repair →

• Failed lower element (electric)

  Most common

  Tell: A small amount of hot water, then cold.

  Fix: Replace the element and test the thermostat.

  Water Heater Repair →

• Broken dip tube

  Less common

  Tell: Lukewarm water quickly; plastic bits in faucet screens.

  Fix: Replace the dip tube.

  Water Heater Repair →

• Heater too small for the household

  Possible

  Tell: Ran out after more people moved in or a bigger tub was installed.

  Fix: A larger tank, a higher-recovery model or a tankless unit.

  Water Heater Replacement →