No hot water or water that turns cold
Separate a fuel, power, flow, thermostat, and recovery problem before replacing parts. Start with the control state and what changed.
Start with no heatField-tested guidance · tank · tankless · RV
Find out why your water heater stopped working.
Start with the symptom you can see. Get the likely cause, the checks that are safe to make, and a clear point where a licensed plumber should take over.
Written around real service-call diagnosis, not product roundups.
A better first visit
01
Describe the symptomNoise, leak, code, or no heat
02
Run the safe checksPower, water, flow, and controls
03
Know when to stopGas, 240 volts, and pressure stay serious
Start here
What is your water heater doing?
No hot waterTank, gas, electric, or tanklessWater is leakingFind the source and limit damagePilot will not stay litGas control and flame faultsBreaker keeps trippingElectric tank and tankless checksA code or light is flashingRead the exact brand and patternRV heater is downAtwood, Suburban, Truma, and more
A clearer way to troubleshoot
Start with what changed, then narrow the system.
Water heaters rarely fail with a helpful label. A cold shower, wet pan, blinking light, or strange sound is the starting clue. The useful next step is matching that clue to the heater type, energy source, and timing of the failure.
Our guides are built for that first pass: identify the symptom, make the safe observations, and stop before the job moves into gas, high voltage, combustion, or pressure work.
How we build the guidesEvery useful diagnosis answers
- What changed?Noise, leak, code, temperature, or ignition.
- What can I safely see?Controls, shutoffs, water source, and timing.
- Where should I stop?Know when a licensed technician needs to take over.
Inside the library
Answers for the way failures actually show up.
The library currently includes 365 focused troubleshooting guides. Each one starts with an observable symptom instead of asking you to guess the part name first.
That matters because “no hot water” can mean a dead element, a gas ignition failure, a tankless flow problem, or a control that has locked out. The right first check depends on the system in front of you.
Search the full guide libraryLeaks, puddles, and relief discharge
Name the wet component first. A fitting leak, drain leak, T&P discharge, and leaking tank have very different next steps.
Start with a leakLights, codes, noises, and shutdowns
Photograph the exact pattern, note when it happens, and avoid repeated resets. The timing often tells you more than the code alone.
Read the code guideTankless and RV-specific faults
Flow sensors, freeze damage, bypass valves, 12-volt controls, and coach layouts need a different diagnostic path than a standard tank.
Explore RV diagnosisBrowse by system
Go straight to your heater type.
125 guides
Troubleshooting
Leaks, noises, codes, shutdowns, and the fastest safe first checks.
View guides 74 guidesGas
Pilots, burners, ignition faults, gas odors, and venting problems.
View guides 83 guidesTankless
Flow faults, cold showers, lockouts, condensate, and brand codes.
View guides 41 guidesElectric
Breakers, elements, thermostats, ECO trips, and heat-pump units.
View guides 42 guidesRV
Atwood, Suburban, Truma, Dometic, and coach water-heater faults.
View guidesMost useful first reads
Popular field diagnoses
Troubleshooting
Rheem Water Heater Not Heating
A Rheem that will not heat is an element, ECO, gas valve, or dip tube. Diagnose by fuel type, then hire a licensed tech.
Read diagnosis TroubleshootingWhat To Do If a Water Heater Bursts
A burst tank: shut the cold inlet, kill energy, stay off the water. Never cap the T&P. Hire a licensed plumber in your zip now.
Read diagnosis GasWhy Won't My Gas Water Heater Stay Lit?
A gas water heater that lights then dies is thermocouple, thermopile, draft, or the gas valve. If you smell gas, leave. Get a licensed tech now.
Read diagnosis ElectricHeater Trips Breaker After a Few Minutes
A breaker that holds, then trips, is a shorted element, wet thermostat, or undersized breaker. Kill 240V, then hire a licensed tech.
Read diagnosis TanklessRinnai Error Code 12: Flame Failure
Code 12 means the Rinnai lit, then lost flame. One reset after you check vents and gas, then hire a licensed tech.
Read diagnosis RVAtwood RV Water Heater Troubleshooting
Atwood/Dometic dead? Split gas vs electric vs ECO vs bypass. Follow this tree, then hire an RV tech.
Read diagnosisBefore you begin
Common questions about troubleshooting.
Can I troubleshoot a water heater myself?
You can safely identify the heater type, read the display or status light, check an accessible shutoff, and note when the problem started. Stop before gas controls, combustion, 240-volt covers, pressure devices, or any area with water near electricity.
Why does resetting the heater often fail?
A reset clears a safety device; it does not repair the condition that caused the trip. A repeated trip can point to a shorted element, blocked vent, flame-sensing fault, dry-fire condition, or unsafe temperature or pressure problem.
How do I know whether my heater is gas or electric?
Look for a gas pipe and burner or vent assembly, or a dedicated double-pole electrical breaker and access panels. Do not remove covers to identify it. The rating plate usually names the fuel and model safely from the outside.
When is a water-heater leak urgent?
Treat a leak from the tank shell, a streaming temperature-and-pressure valve, water near electrical equipment, or flooding that cannot be isolated as urgent. Close the cold inlet only if you can do it safely, keep clear of hot discharge, and call a qualified professional.
Safety before diagnosis
Smell gas, see flooding, or hear a burner bang?
Leave the area when gas is involved, shut off water or power only when you can do it safely, and get a licensed professional involved.
Licensed local technicians
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