Water Heater Not Working? Here's What to Check
If your water heater is not producing hot water, check the pilot light (gas) or circuit breaker (electric) first. Gas: relight the pilot following the label instructions. Electric: reset the breaker and the high-temperature cutoff button on the unit. If these do not fix it, you likely need a professional to replace the thermostat ($150–$250) or heating element ($200–$350).
Cost Breakdown
| Service | Low | High | Notes |
|---|---|---|---|
| Thermocouple replacement | $100 | $200 | Gas models, pilot won't stay lit |
| Thermostat replacement | $150 | $250 | Electric models |
| Heating element | $200 | $350 | Electric models |
| T&P valve replacement | $100 | $200 | Safety valve |
| Tank flush (maintenance) | $80 | $150 | Annual recommended |
| Full replacement | $900 | $3,000 | Tank model installed |
Troubleshooting a Water Heater
No Hot Water At All
Gas water heater: Check if the pilot light is lit. If not, follow the relighting instructions on the label. If the pilot will not stay lit, the thermocouple is likely faulty ($100–$200 repair). Also check that the gas valve is in the ON position.
Electric water heater: Check your circuit breaker panel — the water heater breaker may have tripped. Reset it. If it trips again immediately, there is an electrical problem that requires a professional. Also try pressing the red reset button (high-temperature cutoff) on the upper thermostat behind the access panel.
Not Enough Hot Water
- Thermostat set too low — should be 120°F (factory default)
- Tank too small for your household — see sizing guide below
- Sediment buildup reducing capacity — flush the tank annually
- Dip tube broken — cold water mixing with hot at the top of tank
Water Too Hot
Check the thermostat setting — it should be at 120°F. Higher settings waste energy and risk scalding. If the thermostat is set correctly but water is dangerously hot, the thermostat is malfunctioning and needs replacement.
Strange Noises
Popping or rumbling: Sediment buildup on the bottom of the tank. Flush the tank by connecting a garden hose to the drain valve and running it until the water is clear.
High-pitched whining: Sediment on the heating elements (electric models). Elements may need cleaning or replacement.
Leaking Water Heater
- From the top: Usually a loose inlet/outlet connection or faulty T&P valve — often repairable
- From the bottom: Usually internal tank corrosion — replacement needed
- From the T&P valve: May need replacement ($100–$200) or could indicate dangerous pressure buildup
When to Replace
Replace your water heater if it is over 10–12 years old and leaking from the tank, if repair costs exceed 50% of a new unit, or if you are getting rusty water from hot taps only (indicates internal corrosion).
Related Questions
How long can I go without a water heater?
You can live without hot water indefinitely — it is uncomfortable but not dangerous (except in extreme cold where pipes could freeze). Most plumbers can do a same-day replacement if needed. Plan for 2–4 hours for a standard swap.
Can a water heater explode?
It is extremely rare but possible if the temperature and pressure relief (T&P) valve is blocked or removed. Never cap or plug the T&P valve. If you hear loud rumbling, see bulging at the top, or notice the T&P valve constantly discharging, turn off the unit and call a plumber immediately.
Should I turn off my water heater when on vacation?
Set it to vacation mode or the lowest setting instead of turning it off completely. Turning it off can cause issues with restarting (gas models) and takes hours to reheat when you return. Vacation mode saves energy without the drawbacks.