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What to do if…
you suddenly have no hot water and the water heater shows an error or warning light

Short answer

First check for danger: if you smell gas, hear hissing, or a carbon monoxide (CO) alarm goes off, leave immediately and from a safe location call 911 and/or your gas utility emergency line. If there are no danger signs, photograph the error light/code and arrange service (property manager if you rent; licensed plumber/HVAC if you own).

Do not do these things

  • Do not keep trying to restart/reset a heater that immediately faults again.
  • Do not relight a pilot or open panels unless the manufacturer’s instructions are on the unit and there are no gas/CO warning signs.
  • Do not ignore a CO alarm or symptoms like headache, dizziness, nausea—especially near fuel-burning appliances.
  • If you smell gas, do not operate light switches, garage door openers, or other electronics before leaving.
  • Do not use unvented devices (oven, grill, generator) to “make heat” while you wait.

What to do now

  1. Do a fast safety scan (30 seconds).

    • Gas smell or hissing near the heater or gas line: get everyone out and call 911 and/or your gas utility emergency line from outside.
    • CO alarm sounding or anyone feels suddenly unwell: get into fresh air immediately and call 911.

  2. Stabilize the area.

    • Stop using hot water for now.
    • Keep the area around the heater clear so responders/techs can access it easily.

  3. Record what you’re seeing (this speeds up safe help).

    • Take photos of: the error code/light pattern, the make/model/serial label, and (if visible) the control panel.
    • Write down when it started and whether there was a recent outage, storm, leak, or maintenance visit.

  4. Do only external “no-tools” checks.

    • Electric water heater: check your circuit breaker for a trip (don’t touch anything with wet hands or standing water).
    • Gas water heater: if you do not smell gas, see whether other gas appliances work; if nothing gas-related works, contact your utility.
    • Look for obvious water leaks around the tank/lines. If there’s active leaking and it’s safe to access, you can shut off the cold-water supply valve to the heater. If there’s any electrical hazard (water near wiring/outlets), don’t touch valves—step back and call for help.

  5. Contact the right party and use the info you captured.

    • If you rent: report “no hot water + error light/code” to your landlord/property manager and send the photos.
    • If you own: contact a licensed plumber or HVAC service and provide the photos and model/serial. If it’s under warranty/service plan, use that provider’s service line.

  6. If you consider a reset, keep it conservative.

    • Only do a single reset if the manufacturer’s quick-start instructions are on the unit/manual and there are no gas/CO danger signs.
    • If it faults again, stop and wait for a professional.

What can wait

  • You don’t need to interpret the fault code perfectly or order parts now.
  • You don’t need to decide “repair vs replace” today.
  • You can wait to troubleshoot deeper (pilot, gas valve, venting, sensors) until a qualified tech is present.

Important reassurance

Many heaters shut down to protect you (ignition problems, venting/combustion issues, overheating, or power interruptions). A quick safety check plus getting the right service arranged is the safest way forward.

Scope note

This guide covers immediate safety and first actions only. Your exact steps can differ by heater type (tank vs tankless; gas vs electric) and by local utility guidance.

Important note

This is general information, not professional or emergency guidance. If you suspect a gas leak or carbon monoxide exposure, treat it as urgent and involve emergency services and/or your gas utility.

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