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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.

Direct answer

No hot water at any fixture usually means the water heater lost power (tripped breaker, pilot out on gas, blown fuse on electric), a failed thermocouple or gas valve, or burned-out heating elements on electric tanks. Check other hot faucets — if all are cold, the heater is the problem. If only one fixture is cold, suspect a stuck mixing valve or closed valve. Gas units with a rotten-egg smell or soot require shutting the gas and calling a pro immediately.

Severity and urgency

Fix now for daily living

No hot water affects hygiene and dishwashing immediately. Gas heaters with ignition failure or venting issues can pose CO risk if manually bypassed — do not disable safety devices.

Cost of ignoring it

A small leak at the relief valve ignored becomes tank failure and flooding ($1,000–$15,000 damage). Sediment-heavy tanks that stop heating often mean elements buried — continued operation strains components. Gas pilot issues left unfixed can waste fuel and soot the burner.

How a pro will diagnose it

Plumber checks gas supply and venting, lights or tests pilot per code, measures voltage to electric elements, tests thermocouple millivolts, and inspects for cross-connected dip tubes or failed upper/lower thermostats. Tankless units get flow-sensor and error-code diagnosis. Expect $89–$175 trip fee; thermocouple or element jobs often same visit.

Prevention and maintenance

  • Flush tank annually in hard-water areas to reduce sediment
  • Test T&P valve yearly — lift handle briefly
  • Replace anode rod on schedule to slow tank corrosion
  • Keep clearance around gas heaters per label
  • Know where the water heater breaker and gas shutoff are

For trade owners

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Common questions

Could tripped breaker (electric unit) be causing this?
Check the double-pole breaker labeled for the water heater. Reset once. A repeat trip usually means a failed element or a shorted thermostat and needs diagnosis.
Could pilot light or igniter failure (gas unit) be causing this?
Look through the sight glass at the base of the tank for a lit pilot or a status LED flash code. Follow the relighting instructions printed on the tank. If it will not stay lit, the thermocouple or gas control valve has failed.
Could failed heating element (electric unit) be causing this?
Hot water runs out very quickly, or is lukewarm at every fixture. Electric tanks have an upper and a lower element. 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.
Could thermostat set too low or failed be causing this?
Check the setpoint behind the access panel. The recommended setting is 120°F. Adjust the setpoint. If water still does not heat, the thermostat itself has failed and needs replacement.
Why is there no hot water in the whole house?
Water heater not heating — power, gas, pilot, elements, thermocouple, or thermostat. Confirm cold at multiple hot taps before blaming one fixture.
Electric water heater no hot water?
Check double-pole breaker (both legs). Reset once. If still cold, upper element or thermostat often failed — requires electrical testing.
Gas water heater pilot won't stay lit?
Dirty thermocouple, failed gas valve, or draft issue. Clean pilot assembly only if you are trained — otherwise plumber.
No hot water after vacation?
Breaker may have tripped, gas may have been shut off, or vacation mode on tankless. Check settings before assuming failure.
How much to fix no hot water?
Thermocouple: $150–$250. Element/thermostat: $200–$400. Gas valve: $300–$550. Full replacement if tank leaking: $900–$2,400+.
Is no hot water an emergency?
Not life-threatening unless paired with gas smell or CO symptoms. Same-day service is reasonable for households without backup.
Tankless no hot water?
Flow too low to trigger, error code on display, gas supply, or scale blockage — needs manufacturer-specific diagnosis.
Hot water then suddenly cold?
Different symptom — often dip tube or sediment, not total loss. See 'hot water runs out fast' if showers end cold.
Can I relight the pilot myself?
Follow label instructions only if no gas odor and you are comfortable. If it will not stay lit after one careful attempt, call a plumber.
When replace instead of repair?
Tank leak, rust at base, unit over 10–12 years with major component failure, or repeated gas valve issues.

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.

Water Heater Replacement cost guideRepair or replace calculatorEstimate repair costAnalyze a quote

What the fix costs

Tools for this decision

Other symptoms