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True Trade Path

Diagnostic guide

No Hot Water

Find out why a water heater has stopped producing hot water, for both gas and electric units.

System
Plumbing
Causes covered
8
You can check
4 without a technician

Stop and read this first

  • If you smell gas near the water heater, leave and call the gas utility from outside.
  • Water hotter than 120°F can scald in seconds, and at 140°F in under five seconds. Households with children or elderly occupants should stay at 120°F.
  • A relief valve that discharges repeatedly indicates excessive pressure or temperature. Do not cap or plug it under any circumstances.
  • Turn off power or gas to the unit before working on it, and let the water cool before draining.

Work through these in order

Ordered from most to least likely. Working top down means you rule out the cheap, common causes before paying anyone to look at the expensive, rare ones.

  1. Tripped breaker (electric unit)

    CommonYou can check
    How to check
    Check the double-pole breaker labeled for the water heater.
    The fix
    Reset once. A repeat trip usually means a failed element or a shorted thermostat and needs diagnosis.

  2. Pilot light or igniter failure (gas unit)

    CommonYou can check
    How to check
    Look through the sight glass at the base of the tank for a lit pilot or a status LED flash code.
    The fix
    Follow the relighting instructions printed on the tank. If it will not stay lit, the thermocouple or gas control valve has failed.

  3. Failed heating element (electric unit)

    CommonNeeds a pro
    How to check
    Hot water runs out very quickly, or is lukewarm at every fixture. Electric tanks have an upper and a lower element.
    The fix
    A plumber tests continuity and replaces the failed element. A lower element failure typically shows as a small amount of hot water; an upper failure as none.

  4. Thermostat set too low or failed

    CommonYou can check
    How to check
    Check the setpoint behind the access panel. The recommended setting is 120°F.
    The fix
    Adjust the setpoint. If water still does not heat, the thermostat itself has failed and needs replacement.

  5. Sediment buildup in the tank

    CommonYou can check
    How to check
    Rumbling or popping noises during heating, and reduced hot water capacity over time.
    The fix
    Flush the tank. Annual flushing extends tank life significantly, and heavy sediment insulates the burner from the water.

  6. Failed thermocouple or gas control valve

    PossibleNeeds a pro
    How to check
    The pilot lights but goes out as soon as you release the control knob.
    The fix
    A plumber replaces the thermocouple, or the gas control valve if the valve itself has failed.

  7. Failed dip tube

    UncommonNeeds a pro
    How to check
    Hot water turns lukewarm quickly even though the unit is heating normally.
    The fix
    A plumber replaces the dip tube. A broken dip tube lets cold inlet water mix at the top of the tank instead of at the bottom.

  8. Tank failure

    PossibleNeeds a pro
    How to check
    Water pooling around the base, or rust-colored hot water at every tap.
    The fix
    Replace the unit. A leaking tank cannot be repaired, and a tank above finished space should be dealt with immediately.

Once you know what it is

Step one

Know what it should cost

Get the range before you call, so the first number you hear is not the only number you have.

Step two

Decide repair or replace

On equipment near end of life, the repair is usually the first of several.

Step three

Check the quote

Compare against the typical range and confirm the terms before you sign.

Estimate the repair costAnalyze a quote

What the fix costs

Tools for this decision

Other symptoms